The purpose of this article.
The purpose of this article is to document in detail, my personal tests, and findings of such tests, of the performance of a particular WFCO 9845 Converter/Charger. Call it an, "independent study" if you will, but not to be considered as a "consumer report". It is not meant as an evaluation of WFCO converters as a whole, nor is it intended to instruct anyone how to install a WFCO converter or any other company's converter product. This document is not to be considered an advertisement for any product or company, nor is it to be considered propaganda against any product or company. I will however, at the completion of my testing, offer my personal opinions, based on my test results of what should be considered during an installation of the product I have tested. These opinions should not be considered a strict guideline for any installation, but rather as a basis of comparison for an installation one may wish to undertake. Additionally, this document is not intended to sway anyone's thinking, if considering the purchase of one of these or any other converter product. These tests are to be considered definitive only for the purpose of gathering information concerning a [particular unit] which may or may not be problematic in operation and for the determination of such possible problems with the test unit in particular. I'll provide my results and what I think, you draw your own conclusions.

What started it all.
Some time ago, about a year I'm guessing, I was considering a new converter to replace my 30 year old linear converter with an upgrade to a newer 'smart' switching converter. I wanted something that would provide a 'float' charge and power my rig's 12 v electrical at the same time. My rig was designed such that my converter only powered the 12 volt systems and battery charging was done solely from the chassis alternator. My original converter was not designed to be a charging converter and when I tried using it in that capacity, I found very quickly it would make a very good equalization charger spitting out 16+ volts when connected to a battery load while it attempted to boil the battery to death. This just would not do! So, I began searching the web for converters and read the forums in an effort to help myself with a decision of what to buy. At the time, it was a toss up over the WFCO or the Progressive Dynamics brand converters, but I was having trouble making a decision over which I would get.

When the discussion who's subject appeared as: Parallax 7345 & (2) 6 volt batteries on the RV.net forum (thread dated: 02.15.06), I read with great interest to see what the outcome might me. From it, came much debate about the operation and functionality of the WFCO 98xx series Converter/Chargers manufactured by the World Friendship Corporation. Of particular interest was the dialog between Caseydon and Melm concerning Casey's seeming inability of getting a newly installed unit to perform as expected. Specifically, getting it to function in the Bulk mode of operation.

When Casey continued the dialog with a new thread: WFCO Charger Output (thread dated: 02.18.06), I again read with great interest in hopes I would get some answers to help with my dilemma as to which converter I should get. I was leaning towards the PD brand converter at that point as it was looking like the WFCO was being misrepresented or there were problems with the product. Not only Casey, but others were also complaining of the very same problem with these units not going into bulk mode. Another was RJCorazza, who was stating the very same thing only to find that later on in the thread, he returned his defective converter and was sent a replacement which he claims does the same thing as the first! There still seemed to be no resolve with this and I had made up my mind to go with a PD converter to avoid taking any chances. As it turned out however, I ended up putting the whole converter shopping issue on the back burner for some time to come. My finances wouldn't allow me to invest in a new one at the time and because my old one was (is) still working okay, I really didn't see a need to be in a rush about it.

Several months later, after finances took an upward swing for a short time, I called Bestconverter looking to buy. What I didn't realize at the time, was Randy, whom I'd always thought to be the tech guru, turns out to be the owner and tech guru. This made for easy conversation and even though I was pretty set on a PD already, it gave me the opportunity to ping him for some answers to some of my concerns about the two different brands. Of course the issue of the WFCO bulk mode problem was something that was talked about along with some thoughts about the Charge Wizard of the PD's. Part of the 45 minute long conversation covered ground on the failure rate of these units and I was assured that neither of the converter brands had even a hint of failures that could be considered as, "abnormal". In fact, he stated that of the WFCO's he had only had a very few of them ever returned and of those only a couple were actually deemed by the factory as faulty and the others were returned to him as, "No problem found". That's factory tech talk for, "It ain't broke!". When I mentioned the forum threads I was getting my information from, more details came up and he told me that one of the units was sitting on the shelf and happened to be the very one that RJCorazza had exchanged as being faulty, but had been "blessed" by the factory after it's return. Then to my surprise, he offered it to me for a highly discounted price (without warranty) that was just too sweet to pass up. He said it should be a good unit and the price was right for me, so why not give it a try?

The converter arrived on 08.15.06 and though my rig was never designed to be a "test fixture", it has indeed turned into one, just as other forum members rigs have become home to WFCO and other units where testing has been performed.

Other issues within a more recent thread entitled, Converter Charger - Is it Charging? (thread dated: 05.21.06) will be addressed also.

Lets look at what the World Friendship Co. has to say about the operation of the UUT.....

The Specifications of the WFCO converter.
The WFCO 98xx series (pic) converter manual available on their Website or HERE (download), states the following information:

Each of the various statements will be examined fully during the following series of tests. The rest of the information contained in the manual concerns safety issues, installation, troubleshooting and warranty statements which are not pertinent to the testing process presented here and are therefore excluded in this document. There is mention in the manual that the Bulk mode has a duration of four hours maximum. Of course there are output ratings listed also for each different model number.

As a very important note which pertains to the functionality of the device, there are no specifications given as far as wiring sizes or lengths of any sort which are acceptable for a proper installation. Also noted is, there are no specifications given, as to battery type or amp hour capacity which are acceptable for proper operation of the device. Something I find equally distressing is that the Progressive Dynamics Intelli-Power manual for the 91xx series converters does not contain this important information either! I can only assume, they assume we all just somehow 'magically' know how to install these units and all the other necessary particulars about doing so! Okay! With that, lets continue....

The original test setup.
See the WFCO test setup drawing below for component references in this section. The original test setup consisted of one battery, B2 and 10ga cabling throughout and included the total length of all cables. L1 - L5. The setup included all other devices as they were existing already in the installation. Basically speaking, the test fixture is my rig. The loads presented to the UUT are that of lighting and other apparatus within the rig which are available at FB1. The wiring was all original. The battery was 2 years old (at least) and had been kept on a small float charger for most of it's life. When the UUT was introduced into the system, it was wired in at a location nearer the battery compartment with some cheap jumper cables (10ga) with the clamps cut off and lugs for the battery installed. The main idea at the time was just to see the UUT go into bulk mode. Though the setup was about as hoaky as it could be, it "seemed" like it should work. I proceeded to load B2 down to about 50% SOC and energized the UUT to find it come up in Absorption mode. "OK, good and fine", I thought. I'll just load it again and bring the battery down even further. That didn't work either. So, I brought that poor battery down to it's knees, I mean, LIGHTS OUT! I reapplied power and the UUT still came up in Absorption mode. I didn't try "resetting" it by disconnecting the B2 load, the thought hadn't occurred to me at the time. I just let the battery charge in absorption mode for days after that in hopes it would forgive me for treating it so cruelly. Though this was a total failure, it really got my curiosity up and brought up several questions. Is this unit bad after all? Is there too much resistance in the wiring? Not enough battery capacity? Just what is going on here?

My initial thought was, the UUT was faulty, but because it had been "blessed" by the factory, I had to conclude the test setup was at fault. That left two things which could possibly be amiss. Wiring resistance and battery load capacity. The obvious and least expensive way to go would be to alter the wiring in the test setup, but from the conversation with Randy when I bought the UUT, he had mentioned that the battery load must be able to "accept" the output of the converter to function properly. Ahh, this got me thinking, "Hmm, there's just not enough battery capacity to load the UUT properly". At that point I was in a dilemma about what to do next. Change the wiring or get another battery, change the wiring or get another battery? Round and round I went until, I decided to go against common sense to change the wiring and instead, broke open my piggy bank and ordered another battery, a Trojan J150. In reality, I just needed a good reason to break open the piggy bank and justify the purchase of the J150. I was going to get one anyway, but this simply gave me a valid reason to do it when I did instead of waiting until a later date.

A week and a half later, an impressive J150 arrived home. Not only does this battery make a group 27 look like a group 24 with it's size, it's weight is something to be reckoned with, not to mention the very impressive price of $152 and change! We'll see about it's longevity at a later date. After charging with a trickle charger and topping off the cells with water, I installed the new battery (B1) in parallel with the older Exide (B2) using the L5 cables (6ga) as shown in the test setup drawing (below). The rest of the wiring remained unchanged. Needless to say, testing resumed with hopes that higher battery capacity might resolve the issue of the UUT going into bulk mode, but, as could have been expected, the results were continued failures. This did help resolve the issue of capacity however. Because I now had over double the capacity of my previous tests and the UUT was still failing to go into bulk mode, added capacity was no longer an issue. Now it was either a bad unit or excessive resistance in the wiring of the test setup. The failures of this original test setup of course, got me thinking of things at the drawing board and eventually led back to the obvious.
(Back)

An improved test setup.
Another trip to the auto parts store to pick up a few more lugs and another length of 6ga cable and about an hour later, the new cables were installed. Initial tests with the new setup provided immediate positive results The UUT was observed to function in all the modes (with BOTH batteries) and now I was convinced it wasn't faulty. The obvious seemed true. Too much resistance seemed the culprit of the previous failures and now the test setup looked good. So now, on to the "nitty gritty" testing to see just what the WFCO tic.

The following is a drawing of the test setup which will be used during testing and for all data collection appearing in this document. I would consider this setup not only to be very near optimal for testing purposes, but would be very close to, though not quite an "ideal" installation. The only modifications necessary to call this setup an ideal one, would be to remove the extra shunt S1 and cable L1. Then, shorten the lengths of the cables L2 and L3 by a total length of about 6 feet leaving L2 and L3 at about 3 feet or less each.. In addition, the cables L5 paralleling B1 and B2 could be shortened by as much as 4 feet. Available space within the battery compartment and the larger size of B1 prohibits the shortening of these two cables in my particular installation however, as the batteries will only fit in separate compartments and thus require the extra cable length to connect them together. (Back)

The "Better Than Ever" test setup which is still, not perfect!
On 09.26.06 the Xantrex Communications Kit arrived. It has since been introduced into the test setup. The connection of the interface is block diagrammed below.

This addition to the test setup allows data to be collected at intervals of one second for an indefinite period of time. It has no bearing on the tests themselves but will be used for the collection of some of the test data. We should see very accurate results with the addition of this data collection method. The rest of the test setup remains unchanged. I'll post some screen shots of some of the result gathered during a couple tests using this method. It should prove, very interesting, if not very exciting! Well, okay, maybe not as exciting as beer and nekkid women, but still interesting!

At this point, lets begin with an explanation of the various devices used for the tests. For the sake of simplicity, I'll go down the list as presented in the drawing with a discussion of each item in some (more or less) detail.

B1, B2 the battery load.
Battery B1, as noted in the drawing, is a Trojan J150 (site). This battery is not "considered" to be a "true deep cycle" battery, rather, IS the real McCoy. This is a rather expensive battery with a price tag over $100.00 which is more than I wanted to spend for a good battery, but I wanted a chance to use a real true deep cycle battery for these tests and of course, my own personal usage after the tests are completed. As I have mentioned above, the purchase of this battery was actually spurned by my initial WFCO test failure. During testing, B1 will be included in all of the tests with the exception of one test and will be noted as being excluded.

Battery B2, is a Everstart (Exide) 27DC-6. Labeled a deep cycle battery, I have no reason to believe it's not. It's specs are 115 a/h at the 20 hour rate with a reserve capacity of 160 minutes. This particular battery has no CCA or MCA rating on the label but I've seen a much older identical battery with the CCA and MCA cranking amp ratings of 600 and 750 respectively. When the Everstart site was still active, this battery was listed there and all the specs were available and though this battery is clearly labeled (pic) it's made by Exide, I cannot find an exact match for it on their site. During some phases of the testing process, battery B2 may or may not be included as part of the test load. I will make note of any instance B2 is not included, but otherwise, it can be assumed it is included.

FB1, the load distribution point.
Fuseblock FB1, is the main distribution point of the various loads available used during testing. Of this distribution point, there are basically only two circuits that will be of any concern. Though not really necessary to define these circuits for any other purpose than just loads, I felt I should include the information for the sake of completeness. All loading will be in the form of resistive loads comprised of a number of 12 volt, 18 watt lamps and an additional variable load of a ShurFlo, Polar Aire III vent fan. Each lamp draws about 1.5 amps at about 12 volts (info source) and will be used in combinations of pairs (how my lighting fixtures are wired) from one up to a total of 6 pairs providing a total load capacity of 17.25 amps. The additional variable load of the ShurFlo vent fan similar to the model 275-R1234 (site) and which shares identical power ratings, allows an amount of "fine tuning" of the usable loads, up to and including the lamp load of 17.25, plus the additional 100 ma to 5 amps of the vent fan, bringing the usable total up to 22.25 amps.

M1, the battery monitor.
Monitor M1, is the heart of the data collection. While not quite as fancy as the Xantrex Link10 (manual) or Link 20 and yet a bit fancier than the Bogart Trimetric 2020 (manual) and the Trace TM500 (manual), the Xantrex XBM (manual) (pic) has quite a lot of usable features, just as the other models mentioned. These battery monitors basically all do the same thing, keep an eye on your battery. There are differences however, and I weighed very carefully before I made a final decision to cough up $200.00+ dollars and bought the XBM. The thing that caught my eye about it was that, it has the ability to send any of it's internal information to a computer via a serial connection. This includes any readings and or settings you may wish to access at any time you desire. It allows direct programming of all functions and downloading any or all history information currently residing within the XBM's memory. That's just a real cool feature for someone that can use it and I don't think any of the other models I've mentioned here will do that.

I may come up with much more information and possibly even my own custom software for this at a later point in time. I'll suffice it say for now, I'm forming plans already. As of 09.20.06, I still lack the software to utilize these functions, but that doesn't hinder my testing. It should allow for very accurate testing when the program gets here however. I actually never thought I'd be using my XBM for converter testing, but now I'm really glad I bought the way I did because I'll have the ability to give good hard facts and numbers of my findings. The fact the XBM has communications abilities is just icing on the cake. Northern Arizona Wind and Sun (site) was kind enough to stock the Communications Kit (site) required for the XBM that I'll be using during some of the testing. The XBM itself came from ebay at a slightly lower price with a mfg. warranty.

PS1, the original converter.
This converter is unused in all tests. It's purpose will be to provide 12 volt power to the external loads during periods of testing when no loads are required. It will be referenced in some portions of this document, but has no other part in the actual testing of the UUT. It provides a means to utilize the 12 volt electrical within the test setup to continue to provide the comforts of home.

S1, S2, the shunts.
The shunts that will be used for testing, are the typical common shunts available where ever quality battery monitors are sold. S1, the 100amp/100mv (pic) shunt is a low current high resolution shunt. It's location in the positive cable between UUT1 and B1, B2 provides a method of measuring the TOTAL output current UUT1 is supplying to the FB1 load circuits. This includes battery load and all external test loads available from FB1. It's actual use in the tests will be minimal and is basically used as a means to verify the charge/load rate readings of the XBM through shunt S2 (which only shows B1, B1/B2 charge/discharge current, and not UUT1 load current).

S2, the 500amp/50mv (pic) shunt is a medium current, medium resolution shunt. It's location in the negative cable between UUT1 and B1/B2 only allows the monitoring of the voltage and current levels going in or out of B1 and B2 during testing. It does not see any current supplied by UUT1 to FB1. It is this shunt the XBM connects to and monitors only battery activity.

SW1, the external load switch.
This switch is not really part of the testing process, but rather original equipment installed within the rig. It's purpose is to select where power to FB1 is sourced from. In the original design, this switch is used to pick either the original converter (PS1) to power the 12 volt electrical system when shore power is available, or, select the battery as the source of power when shore power is unavailable. It does have it's purpose during the testing process by providing a means of switching in and out the external loads to allow continued operation of them, thus enabling me to continue to live in comfort!.

UUT1, the unit under test.
There's not really too much to say about the UUT as it's already mostly been said. It's a 9800 series 45 amp WFCO converter which replaced the 8800 series. The only difference that I know of, is that this version incorporates the 'brain' within the unit itself, much like the new PD 9200 series converter does. The older 8800 series had a remote brain similar to the PD 9100 series and Charge Wizard which allowed an amount of manual control of the unit. As I've stated earlier, this converter was blessed by the factory as a good unit. With that in mind, I intend to delve into as much of the inner workings as I can to see what makes these converters tic.

L1 - L5, the cabling.
According to Mark Nemeth's (site) cable chart located here, 6ga cable is good for current levels up to 50 amps at lengths up to 13 feet . As can be seen from the drawing, the test setup total cable length of 14 feet between UUT1 and B1 which falls just outside this wiring criteria by only 1 foot of extra cable. This should be inconsequential for the various tests and therefore should prove to be a proper test installation. If failures are noted, further modifications to the test setup may be required to eliminate the test setup as a cause of testing failure. Shortening of the cables should suffice, if required.

Note: No disconnect switch!
As a final note in the description of devices, you'll notice there's no battery disconnect switch or solenoid residing within the circuit. For this reason, the battery load for all but the Converter Mode test will be applied continuously and without interruption during each test up to the point where the Converter Mode test phase is completed. Some or all of the tests may possibly be repeated with the manual interruption of this circuit connection in an effort to simulate such switch or solenoid. The method which this will be accomplished will be made by the manual removal and reconnection of one end of cable L4 of the battery charging circuit. Results of those tests will be dully noted at that time as RESETTING.

The results of this test setup, though not a complete disaster as was the "Original" test setup, did provide a lot of useful timing information but was still deemed an overall failure during the Mode Switch Tests. This, of course, led to....

The Installation test setup (Successful, preliminary results have been obtained with this setup) 10.17.06
Because of the test failures of the Mode Switch tests and the burning curiosity to know that the test setup is sound, the final alteration of the setup has been completed. The setup can be considered a proper installation because of these minor changes. As of 10.17.06 the cables, L2 and L3 have been reduced in length. L2 is now 1 foot and L3 is at 2 feet, reducing the overall cable length by a total of 8 feet. This is a reduction of 66% of the wiring between UUT1 and B1. The total cable length between UUT1 and B1 is now at 6 feet. This change should eliminate any possibility of cable resistance of the test setup causing any erroneous results. If you examine the chart, this setup falls in at the 65-85 amp rating of 6ga cable at a length of 6 feet. This represents a current carrying ability of at least 20 amps and up to 40 amps over the labeled rating of the UUT. At this point, I will consider the issue of wiring and excessive resistance as resolved. If the UUT continues to fail the Mode Switch tests, it is because of either not enough battery load or the UUT just fails the tests. I'm expecting the UUT to pass these tests with the single B1 load, but we shall see. There is the possibility the UUT just requires more than a 150 ah battery load to function properly. I believe most users that are experiencing positive results with these units are probably running at least 2 batteries, likely totaling over 200 ah capacity. If positive results are obtained with this setup using only the B1 battery, then the capacity issue can be put to rest (at least to a point) and proves wiring resistance plays the most important factor for proper operation of these converters. Again however, these are my own personal experiences. (Back)

The definitions of the various tests.

Functionality testing
To determine whether or not the unit functions as described within the contents of the user manual and advertising statements. This includes, but not limited to the following items of main concern to users of the device:

Voltage measurements
Does the unit output the described voltage values? What are the real measured values?
All RV power converter are design to operate as a "constant voltage" source. This means the output voltage is to remain constant at all times with respect to current output. Single stage converters are designed to operate at one specific voltage, usually around 13.6 to 13.8 volts. Multistage converters provide a means of varying the output voltage either manually, automatically, or both, to different specific voltage levels while maintaining a constant voltage under varying loads at each set predefined output voltage. The WFCO 98xx series converter falls into this category of converter with three predefined output voltage levels of, 13.2, 13.6 and 14.4 volts.

Current measurements
Does the unit output the described current values? What are the real measured values?

Mode switching and mode switch timing
Does the unit switch modes as described and what is the actual timing of these functions if they differ from the manual?

Tests which will not be included within the testing process are, power consumption, line voltage Vs output regulation, overload protection and RFI noise radiation.

The Tests.
There are two modes the UUT can operate in which do not include the familiar Bulk, Absorption, Float and Desulfate modes. Rather, I speak of, Converter and Converter/Charger modes of operation.
Converter mode: implies, the UUT will supply current only to a varying load with no battery load applied.
Converter/Charger mode: The UUT will supply current to battery and varying external loads.

Converter mode implies, the UUT should provide output to varying load conditions with no battery load present at the output of the converter. Because no charging is involved in this mode of operation, the output should remain stable and constant under all conditions up to the UUT's rated output. This test is considered useful for those people with rigs where the original converter does not provide battery charging and when such charging of the battery is applied, it is provided by the chassis alternator or other means external to the coach's on board converter. My rig falls into this category. Back

The manual has these first two (actually three) statements which apply to the "converter" mode of operation.

The following first snippet from the manual is true for both modes of operation during the UUT's power-up cycle. It really contains two statements. The first, being that of the control electronics being located internally and the second, being that said controller performs testing to determine the initial sub mode it will enter at that time. This really should have been separated into two sentences and looks like a simple typo error.

The following statement applies to Converter Mode operation, but not limited to this mode on power up.

The rest of the statements apply to the Converter/Charger Modes of operation.
The following statements all apply to general mode switching.

It's unclear exactly what this means. Does it mean it'll just check and do nothing or, check and switch sub modes? Is it overload control?

The next statement apparently contains another typo error.

Stating that 13.2 volts is the bulk mode trip point, and that 13.2 volts is the 50% DOD discharge point is nonsensical when 13.2 volts is considered to be a charged battery's float voltage. They're stating basically, anytime the voltage drops below the float point, the converter switches into bulk mode. The 13.2 volt reference should likely read 12.2 volts instead. ....And where did they get the idea to call it Buck mode anyway?

This seems pretty straightforward, we'll see if it's true or not.

Is this time or voltage dependent, or both? We shall see.

This statement will be examined during the Mode switch timing from power-up tests.
Once the phase 1 timing test is completed and it's data gathered, (timing measured with no load), phase 2 of the test will be conducted with a constant minimum load plus other extra variable external loads.

The final statement is a redundant statement from the previous one about switching into float mode from a previously resting state with no external load.

....And so, the experiments begin....

Test Descriptions.
Detailed descriptions of the various tests which will be conducted are in the following section. Results of the tests follow in the Results section.

During these tests, the following applies concerning the loading of the UUT. Currently I can only provide a maximum load of about 25 amps. Additional testing at a later date may be performed with loads at and/or above the rated output of the UUT. All voltage measurements will be read directly at the UUT. Voltage vs. SOC charts will not be used as an indication of battery SOC or DOD during any testing procedure. The battery monitor, M1, will be relied upon for the determination of SOC and DOD.

Voltage tests (Results)
Description: The test will be conducted in two phases. Phase 1 will be considered applicable to the Converter mode of operation and will be conducted in the following manner. There will be no B1 or B2 battery load connected to the UUT at any time during testing. A no load condition will be presented at the output of the UUT. The UUT will be powered up and the output read and recorded. Varying loads will then be presented to the UUT up to the maximum available load of at least 20 amperes and the output monitored for voltage stability and the results recorded. The UUT will be powered down. Varying loads will be present at the UUT output up to the maximum available load of at least 20 amps and the UUT will be powered up with each varying load and the voltage output will be recorded for each test.

Phase 2 of the voltage testing will be conducted in the Converter/Charger mode in the following manner: The B1 battery load will be present at the onset of power-up of the UUT. The UUT will be presented with varying loads up to the total available load of at least 20 amps and the results will be recorded for each test. During the periods of each sub mode, the UUT will be presented with varying loads as in the initial test and the results recorded. Some results will be gathered during the second phase of the "Mode switch timing from power-up" test.

Current tests (Results)
Description: Current testing will be performed with battery loads applied to the UUT to determine the output capability of the UUT.
With the addition of the XBM communications kit, current measurements will be derived from graphical data. Only battery loads will be presented using this method. This is basically a pass or fail test.

Mode switch from power-up in Converter/Charger mode. (Results)
Description: The tests will be conducted in two phases, with two rounds in each phase. Each round will consist of at least three test results.
Phase 1 tests will be made with B1 as the only battery load.
Phase 2 tests will be made with B1 and B2 as the battery load.

Round 1 of each test phase will be with power reapplied to the UUT operating from a previous resting output voltage as defined as the Float mode voltage of 13.2 volts.
Round 2 of each test phase will be with power reapplied to the UUT operating from a previous resting output voltage as defined as the Absorption voltage of 13.6 volts.

During each test, the B1 or B1/B2 battery load will be brought to a DOD and voltage level believed to be sufficient to trigger the UUT to switch from it's previous operating mode to Bulk mode charging. Input power to the UUT will be disconnected during this period. When the battery SOC reaches a DOD test level, the UUT will be re-powered and the resulting mode will be recorded. A discharge load representing at least 20 amps may remain in circuit at the onset of power-up and will be noted in the test results. The discharge cycle will be repeated until the UUT successfully switches from it's previous operating mode or until it is determined by excessive DOD that the test is a failure. Voltages will be measured at the UUT output terminals, monitored for a sufficient amount of time to determine without question the result of a test. DOD will be measured by M1. When the additional B2 load is to be reconnected to the circuit, B1 will be fully charged and the B1,B2 pair allowed to equalize under charge for at least a 24 hour period before testing resumes with the phase 2 tests.

Mode switch timing from power up. (Results)
Purpose: To gather actual timing data of the automatic mode switch functions and to prove or disprove whether loads or no loads alters the timing.
Description: The test will be conducted in two phases. Both phases of tests will be conducted in the following manner: The B1 battery load will be at or near 100% SOC (90% SOC minimum). The UUT will then be reset by removing power and disconnecting B1. After a period of time, B1 will be reapplied and the UUT will be powered up. The UUT will be verified to be operating in Absorption mode and at that time the test is considered started. The UUT will be allowed to operate for a period of time believed to be of sufficient length to observe all automatic mode switching events including at least two desulfation cycles. Data will be captured via serial device and will be extrapolated at the conclusion of the test. Each test phase duration is estimated at about 100 hours.

Phase 1 test will be without FB1 load as provided via SW1.
Phase 2 test will be with the FB1 load available with a minimum continuous load of 3.5 amps plus additional varying loads of up to 20 or more amps.
Below is a chart that depicts the theoretical operation of the WFCO from a power-up state. The actual timing will be added to the results chart at the completion of the two tests.

Functionality tests, the results. (As of 10.21.06 in process) (back)
Please note: All actual graph timing is represented as: 0:00:00:00, days, hours, minutes and seconds respectively.

Voltage tests (As of 11.24..06 partially complete) (back)
Phase 1 test (not started)
The converter mode voltage test has a lower priority than the rest. I will however post this information when the test is completed.

Phase 2 test (Concluded 11.24.06)
The table below shows measured output voltages from the UUT:

Current tests (Concluded 11.11.06) (back)
Current testing results reveal that not only does the UUT output the labeled rating, but a substantially higher output under even light battery load conditions (84.6% SOC with the B1/B2 pair). From an expanded snippet of the graph generated from one of the Mode switch tests (Phase 2, Round 2, Test 3), current output of well over the rated output can easily be seen from the onset of power up, lasting for several minutes.
Test evaluation: Passed.

Mode switch from power-up in Converter/Charger mode. (Back)

Phase 1 (B1 load)

Round 1 (from Float mode 13.2 ), test started 09.23.06. (As of 09.25.06 completed)
Test 1, At 11.62 volts, failed to switch into bulk mode.
Test 2, At 11.45 volts, failed to switch into bulk mode.
Test 3, At 11.37 volts, failed to switch into bulk mode.
Test ended.

Round 2(from Absorption mode 13.6) test started 09.25.06 (As of 09.25.06 completed)
Test 1, At 12.03 volts, failed to switch into bulk mode.
Test 2, At 11.94 volts, failed to switch into bulk mode.
Test 3, At 11.74 volts, failed to switch into bulk mode.
Test 4, At 11.61 volts, failed to switch into bulk mode.
Test 5, At 11.45 volts, failed to switch into bulk mode.
Test 6, At 11.25 volts, failed to switch into bulk mode.
Test ended.
Test evaluation: Failed.

These results are nearly the same results as those obtained with the original test setup, but because I've already seen the UUT perform correctly with the additional load of B2, and now it's back to it's old tricks, the cable resistance factor again falls into play and will have to be eliminated as a possible suspect for these failures. Meanwhile, timing and desulfation testing will be conducted with the current test setup.

Additional:
During phase 1 testing, preliminary results indicate as long as the battery load remains connected to the UUT, it retains the mode at which it was previously operating. Obviously, the UUT does not respond strictly to the voltage presented at the output terminals during power-up as the manual states and this suggests load sensing Vs voltage sensing or the possibility of both are required for proper operation.

What effect does RESETTING (tricking) the UUT have?
In float mode with B1 at 100% SOC, the UUT entered Absorption mode.
In absorption mode at 0.5 amps charge current and 20 amp load applied, the UUT reenters Absorption mode.
In absorption mode at 29% SOC, the UUT enters Bulk mode.
Resetting the UUT when the B1 load is at a relatively high SOC, the UUT enters Absorption mode.
Resetting the UUT when the B1 load is at a significant DOD, the UUT enters Bulk mode.
This may imply that mode switching could be an "and" function. The voltage must be at or below a specific level AND the current draw must be at least, "so much" to trigger the switch function, but as of yet, is unknown.

At this point it seems apparent with the current test setup and battery load of only B1, the converter will not power up in Bulk mode from a previous state of either float or absorption modes. I consider this in reference to the manual as a possible failure. This could still be because the test setup is not 'stiff' enough and could possibly indicate the L1 - L4 cable lengths are too great in the test setup. At a later time, I'll repeat a cycle or two of this test after shortening some cables of the setup. If, after shortening the L1 - L4 cable lengths the same results are obtained, I will consider this as a possible UUT failure. Otherwise it indicates the UUT passes this test and it is the test setup which is at fault. This applies to testing with ONLY the B1 load. Previous undocumented tests with the B1/B2 load applied, as stated previously, have already confirmed the UUT will switch modes without resetting, so there is still a possibility the UUT just needs more load capacity, but without changing the setup again, it goes unverified.

After modifying the "Improved Test Setup"
to the "Installation Test Setup", (10.17.06)
I can finally report SUCCESS with the Mode Switch test!

Phase 1 (B1 load) retests

Round 1 (From Float mode 13.2 ) Test started 10.22.06(As of 11.01.06, on hold.)
Test 1: Failed. Test performed with a 20 amp constant load applied until it was deemed a failure. To be repeated.
Test 1: Re-test Passed

Round 2 (From Absorption mode, 13.6) Test started 10.18.06 (As of 10.20.06, concluded)
Test 1: Passed. Test performed with a 20 amp constant load applied through the entire cycle.
Test 2: Passed. Test performed with a 20 amp load removed after power up.
Test 3: Passed. Test performed with no external loads applied at power up. Test repeated until UUT1 powered up in bulk mode.

The Phase 1 Round 1 test failure yielded some really interesting results (see the graph). Even though the test is a failure initially, the graph shows the current being manipulated by the 'brain', which has previously been unseen to the extent the graph shows. This may lead to determining just how the UUT 'decides' when to switch modes during a charge cycle. This test will be repeated with a deeper discharge level so I can compare the results. Note these observations have been seen only while powering up from Float mode.

Phase 2 (B1/B2 load)

Round 1 (From Float mode 13.2 ) testing started xx (As of xx not started)

Round 2 (From Absorption mode 13.6 ) testing started 11.02.06 (As of 11.04.06, concluded)
Test 1: Passed. Test performed with a 20 amp constant load applied through the entire cycle.
Test 2: Passed. Test performed with a 20 amp load removed after power up.
Test 3: Passed. Test performed with no external loads applied at power up. Test repeated until UUT1 powered up in bulk mode.

Questions on Bulk Mode:
Q: What effect does power cycling (Not resetting) have if the UUT is already in Bulk mode?
A: With the B1 load at 98% SOC, with or without an external load applied, the UUT remains in Bulk mode. (This could be bad! ESPECIALLY for AGM batteries if the timer gets reset with a near full charge.) With the B1 load at 29% SOC, with or without an external load applied, the UUT remains in Bulk mode. (This is as expected)
Q: Does the timing of the bulk mode reset at the onset of power-up, or does it resume from where it was? (Is it possible to overcharge the crap out of your battery?) Unknown, but I believe, yes! ESPECIALLY if the timer gets reset on power-up!!!
Q: If the UUT never goes into bulk mode, does this mean it won't go into desulfate also?
A: No, the UUT will go into desulfate mode if the UUT is resting in float mode and the voltage requirement during the desulfate T1 cycle is met.

Mode switch timing from power up. (Back)
Phase 1 Begun: (On Hold)
This test requires vast amounts of time to gather data, with each test phase requiring a calculated minimum of 97 hours to complete.

Because the first test was invalidated due to unforeseen computer problems, this test is going to be repeated.

The following graph (11.24.06) shows the timing from power up after a deep discharge cycle. The battery SOC was at 50% at power up and the UUT had been previously operating in float mode. It's interesting to note the timing from bulk mode to float mode in this instance was only 24 hours compared to the 72 hour timing when powered up from a reset state. Note also the two small downward blips in the righthand side of the graph. These are the T1 timing points (see the desulfation section for more detail on T1 timing) when the converter decides whether or not to go into the desulfate mode. Because there was no external load applied to bring the battery voltage down to the trigger point, the desulfate mode was skipped. This graph was made with the B1 and B2 battery load. This verifies the fact that if you want the converter to go into desulfate mode, there must be an external load applied to the batter(y/ies) to bring the voltage down to the trigger lever while within the T1 timing period, otherwise the desulfate mode is skipped altogether. It took 6 days to log this data which included the discharge time (not shown).

Though not part of the proposed timing tests, here is shown the absorption timing from the end of a bulk cycle to the first float cycle.

Desulfation mode as of 09.07.06 (preliminary, manually collected data).

This is without a doubt the hardest test of all to manually observe. Reason being, the only way to get to the desulfate mode is to let the UUT operate solely on it's own. There's nothing that can be done to trigger this mode so all that can be done is to wait and the wait is a long one. From a power up situation from when the UUT enters absorption mode, it takes 72 hours to get to float mode. Once in float, it takes another 24 hours just to get to the first desulfation cycle. After that, the next cycle is 25 hours away! Gathering this data manually is much more difficult than it would seem and one test the XBM communications kit will hopefully help to resolve. Preliminary observations, though not very accurate or even complete, do yield the following results at this point in the testing of this unit.

The desulfation mode testing is probably not really all that important to anyone and just the fact that the UUT actually does it, is probably good enough for most people. Full timers may find this information invaluable however, as once the UUT is powered up and reaches the first Float cycle, the UUT seems to operate solely between the float and desulfation modes. Further load testing will have to be performed to confirm this, but for now seems to hold true.

In a nutshell, the UUT enters this mode at about 25 hour intervals. So far as seen, about 25.25 hours is actually closer to the mark and because of that extra time over 24 hours, this alters the time it'll go into this mode 24 hours later. This means that after each cycle it will enter this mode at a later time than it did the time before by at least 1 hour with every cycle. So don't plan to ever set your watch by looking at your battery monitor! The desulfate cycle lasts for 1 hour, then the UUT returns to float mode.

For the rest that really want to know what's happening, I offer the following additional information I've gathered so far. Below is a small chart to help illustrate my observations up to this point with this mode of operation. It shows basic timing only. A little explanation my be in order here. The long lines labeled T3, represent the points in time where the UUT is in float mode. In the expanded circle, the horizontal lines represent a duration of time, while the vertical lines represent a change in events. When the line dips down, this is a period of zero output from the UUT. When it raises upwards, the UUT is in desulfate mode. When in-between the no output and bulk output modes, the UUT is in float mode.

When switching from float mode to desulfate mode, the following events and results have so far been observed and noted. After a period of time as measured from the end of the last desulfation cycle, about 24 hours (24 hours and 20 minutes) The output of the UUT shuts off completely for an as yet undefined and possibly variable period of time labeled as T1. The UUT voltage slowly drops to a value of 12.62 volts with a 3.2 amp load applied over a period of about 8 minutes. Once this voltage was reached, output resumes in desulfate mode. Initial output current is moderately high, over 20 amps. Within 5 minutes, the current dropped down to 2.7 amps continuing downwards slowly to roughly 1 to 2 amps for the remainder of the cycle. This represents only a trickle charge to B1 and B2. The measured voltage was 14.62. The frequency of this event may be somewhat dependent on whether an external load is applied during the onset of the T1 event. The duration of the event from the point of resumed output, the start of T2, to the end of the cycle, the start of T3, is measured at about 60 minutes.

From the chart above, the following is known so far:

T1 may be defined by time or possibly voltage and will be variable if found to be voltage related. Time dependency would be that the T1 cycle is always a fixed length of time. Voltage dependency would be defined as the period of time from when the T1 state is entered, until the sensed voltage at the UUT output reaches a terminal voltage, which is so far thought to be 12.62 volts.

T2 is always 60 minutes in length and represents the duration of the active desulfation period. The voltage output of the UUT when in this state is measured at 14.62 volts.

T3 may be somewhat dependent on the length of T1 but is always at least 24 hours PLUS the 1 hour desulfation period and may quite possibly include the T1 timing which is also not yet verified. Because of the additional timing of the added T2 timing, this creates a skewed affect as to when the UUT will enter it's next desulfation cycle.

With these preliminary results, we can see the skewed daily timing of the UUT desulfate mode to look something like this:

The timing shown on the chart is not meant to show exact timing, but rather a representation of the skewed timing effect. This illustrates why one day you may notice a WFCO going into desulfate mode at a particular time, but not again at that same time 24 hours later. This is one of the reasons gathering this data is difficult. Another is the fact that the T1 timing is of a relatively short duration, so far measured in only minutes. More accurate results on this are expected with the addition of the XBM comm kit.

Actual Data on the desulfate mode (10.12.06 On Hold)

From the point the UUT enters float mode, until it begins the desulfate cycle, the timing is nearly exactly 24 hours. The beginning of the desulfate cycle is represented as the point in the graph where the UUT shuts off it's output, as shown by the small dip below the float voltage. (See the expanded circle for timing and voltage details). I believe the 15 minute period of time the UUT's output is at zero, is the period where it decides whether or not to enter the desulfation mode. I believe that, if the voltage doesn't drop to a predefined level (12.6...something) within the 15 minute T1 duration, the UUT skips the desulfate mode and stays in float mode. As you can see the voltage only dropped 0.20 volts within the 15 minute time frame and the UUT never went to desulfate, which would have happened where the sharp green spike in the current level is located at the end of the UUT's monitoring period. If however, the voltage does reach the predefined level within the allotted 15 minutes, I'm thinking, the UUT will immediately go into the desulfate mode, disregarding the rest of the allotted decision making time frame. If this is true, then the T1 timing as described in my preliminary, manually acquired observations, becomes variable as I suspect. The way to prove it would be to put a couple different loads on the battery to bleed off the surface charge at different rates. A light load to bring the charge down slowly, but within the 15 minutes and see what happens. Then before the next cycle, put a heavier load to bleed off the charge more quickly. Then, comparing the results would prove if the decision to go into the desulfate mode is actually voltage dependent. This is all transparent to the typical user, but is invaluable for diagnostics and just knowing what the hell is going on!

In an attempt to prove this theory, I've begun a new test. The UUT, while in float mode, was presented with a load of about 5 amperes for 5 minutes. The purpose, to designate a starting reference point for the beginning of the test. After the initial 5 minutes, the 5 amp load was reduced to that of 3.6 amps for an additional 5 minutes and represents that actual, FIRST, test load. The UUT was then powered down for an additional 5 minutes and then re-powered. It was verified to remain in float mode and the affect of power cycling may prove timing as far as, if the UUT resets it's internal clock with the application of power or continues the timing cycle uninterrupted. If it takes something different than 24 hours after a power up while in float mode, this indicates the timing is independent of the application of power. If the UUT attempts another desulfate cycle at a time period of nearly exactly 24 hours from power up, the internal clock can then be considered reset from a power up cycle, thus the requirement for a test starting point. If the addition of the load applied changes the length of the T1 period from the previous results from the graph above, the decision can be assumed to be voltage related, whether or not the UUT actually goes into desulfation, which could still be battery load dependent. Another test, with an even heavier load should confirm the decision making timing. The battery load may or may not make the difference as to whether or not the UUT actually goes into desulfate and then again, there's still the cabling issue, but the results of this test may solve many mysteries and will be interesting at any rate.

10.06.06 After three days of solid data collection, the following results have been obtained. Though the graph doesn't seem as it shows much, but there's really quite a bit of information that can be retrieved from it. From the graph below, it can very easily be seen, each desulfation cycle over the three day collection period. Using expanded portions of this chart, all the timing information can be obtained concerning the desulfation mode. These results confirm my manually obtained observations and gives us the real numbers.
From power up, the timing to the first T1 cycle is measured at 24 hours and 19 minutes. This confirms the internal timer was reset on power up.

Expanded data can be seen from the following graphs concerning T1 timing. These graph snippets (expanded from the graph above) show that triggering of the T2 (desulfate) cycle is dependent on two factors. The first being that T1 is limited to a maximum of about 16 minutes. The second being, the voltage must drop to the trigger level, which can be seen as almost exactly 12.6 volts. This must happen within the T1 time period in order to begin the T2 period. This can happen in two ways. First, if the battery voltage drops to the trigger level due to it's internal resistance which lets the surface charge dissipate rapidly enough to reach the trigger voltage, or secondly, from an external load that will dissipate the surface charge to the trigger voltage within the T1 period. In either instance, T2 begins immediately once the trigger voltage is reached. If the trigger voltage is not reached within T1, the T2 period is skipped. This means the UUT will never go into desulfate unless the trigger voltage requirement is met within the T1 timing period.
Graph 1 shows the timing with a 0.0 amp load present during the start of T1.
Graph 2 shows the timing with a 1.8 amp load present during the start of T1.
Graph 3 shows the timing with a 3.2 amp load present during the start of T1.
Graph 4 shows the timing with a 6.0 amp load present during the start of T1.

As far as T2 timing, the result is repeatable and set at nearly (but not quite) exactly 60 minutes, so the graph confirms that each desulfation (T2) cycle is programmed to approximately 60 minute duration.

There's more data to be extrapolated from the three day graph, I just haven't gotten to it yet.

Additional experiments on desulfation.(B1 load only)
These tests are designed to find out how the timer responds to power cycling at different periods of times within the desulfation cycle. Much time and effort is going just into these tests and they take forever to get any information at all because of the timing cycle of the UUT. Only one test per day can be performed, so with each test, it takes at least 25 hours to perform another.

What is the effect of power-cycling the UUT while in T1?
This produced some bazaar results, which I'm currently still collecting. (10.11.06)
Basically, doing this put the UUT in Bulk mode (4 hours) and then went to Absorption. This test may have opened a can of worms, as I was trying a couple different things at the same time. Because I foo-bared the test, I'll have to redo it. The idea was to let the UUT go into T1 and do a simple power cycle to get the results. I was expecting the same results as the test that follows this one. Thinking I was going to get the same results, I decided I'd try extending the T2 period by doing a couple extra power cycles within the test. After that, I let the UUT run thinking it was going to go back into float mode an hour after the last power cycle. Instead, the UUT went into Bulk mode for 4 hours and then went to Absorption mode.

What is the effect of power-cycling the UUT while in T2?
There are actually two (three? or four?) questions that might be answered here.
The first would be, what happens if the UUT is already in T2 and the power is cycled while still within the T2 period?
To answer this question, the UUT was allowed to go into a desulfate cycle with a load applied. Once in T2 for about 30 minutes, all external loads were removed and the UUT was powered down (not reset). Approximately 10 seconds later, well within the point the T2 cycle would normally end, the UUT was re-powered. Upon power-up, the UUT resumed the T2 period continuing until the normal end of the period, then fell back into float mode.
This is another test I'm going to repeat as I want to see what happens while a load is still applied. As you can see in the graph, the voltage level dropped only slightly within the time the UUT was powered down. When the test is repeated with a load, I'll leave enough time for the voltage to drop to the trigger voltage and then repower the UUT.

The second would be, what happens if the UUT is in T2 and the power is cycled off at that time, but then returns again at a time outside the T2 period?
(Concluded 10.08.05)
To answer this question, the UUT was allowed to go into a desulfate cycle with a load applied. Once in T2 for several minutes, all external loads were removed and the UUT was powered down (not reset). Approximately 1.25 hours later, well past the point the T2 cycle would have normally ended, the UUT was re-powered. Upon power-up, the UUT restarted the desulfate (T2) period and continued for the full length of the cycle, one hour.

It's unclear if this behavior is present in the other modes, but this test shows the timing function was dependent on power being applied to the UUT. Power-cycling reset the timer to the beginning of the current mode or cycle.

The UUT has not yet been seen to enter the desulfation mode unless it is resting in the float mode previously.

The Hard and Software of it all.
From the hardware aspect, a block diagram of the UUT might look something like this:

From the software side, a (preliminary) flow chart for the UUT might be similar to:

This is a very simplistic example of how the flowchart might look, there are other things that go on during charge cycles which are not presented in this diagram. This chart is simply a basic depitction of what the converter may do during initial power up.

Additional notes and comments.
Some of the earlier WFCO models (8800 Series) included a remote module which allowed manually switching between the different sub modes of operation. This was discontinued in the 9800 series, presumably because users who override the automatic function and forcing the converter to operate in bulk mode too often, may cause premature battery failure due to excessive overcharging. According to a reputable source, "The average consumer does not really know the actual state of discharge of their battery bank at a given time because of varying loads throughout the day. Most OEM battery indicators are unreliable and inaccurate in determining depth of discharge. Starting an onboard generator for instance might cause a significant voltage fluctuation. Forcing the bulk mode will virtually always cause gassing and if used too often, will not only use excessive water, but might damage or shorten the life of the battery." Additionally, while in the automatic mode, The WFCO will not necessarily stay in bulk the entire four hours if the current and load sensing determines a shorter bulk phase is required. Overriding and forcing a unit into bulk will always run the full four hours (applicable to PD converters).

Please note that the WFCO 98xx series converters may or may not operate with the desulfation mode. I have heard that different versions of these converters may or may not incorporate this mode of operation. Because of this, you may or may not experience your particular converter operating in this mode. I know of no way to tell which version any of these converters might be, with possibly the exception of the individual unit's serial number. As of 09.21.06, I'm trying to obtain any information to tell, or even whether this is factual or not. If this information becomes available, it will be presented here. Note also, the current manual makes no reference of the desulfation mode!

It was discovered in an almost shocking manner, the negative terminal of the WFCO is electrically connected to the case (ground) of the unit. This means, be careful when testing voltages directly at the terminals. Getting a test lead in the wrong place when probing the positive terminal while it's live can cause a full power short to ground if the probe tip contacts the positive terminal and the case at the same time. I have a well melted test probe that proves this beyond any question!

My conclusions (so far).

On installation:
As can be seen from the progression of the test setup from the "Original" setup to the "Improved" setup to finally, the "Installation" setup, the issue of wiring is a major one. In fact, probably the greatest issue of a good installation. This holds especially true if using only one battery in the coach. Obviously a certain amount of "stiffness" in the wiring is required. With more battery capacity, the stiffness becomes a little more lax, but still plays an important part for a good working installation. Even in the "Original" setup, added battery capacity didn't improve the results, but heavier cabling did with the "Improved" setup and using two batteries (those results are undocumented in this article). This means there's a basic minimum capacity/resistance ratio that the converter works properly with which must be met. With the results I've obtained, I feel as though I'm right at the beginning of the "sweet spot" for proper operation with both a single and dual battery load and the length and size of cable used.

From these experiments, I would recommend to anyone installing any of the popular "Smart" converters:
1. Wire it in like an Inverter. Use heavy cable and wire it directly to the batter(y/ies).
2. Use as short a cable run as possible, preferably no longer than 6 feet for the total length of BOTH cables (3 feet ea.).
3. For converters rated less than 60 amps, use at least 6ga cable. I wouldn't recommend 8ga even for a 35 amp converter.
4. For converters rated at 60 to 80 amps, use 4ga cable. See the tables below for other cable lengths.

For systems with one battery:

For systems with two or more batteries:

On Batteries:
As we've seen with wiring, capacity plays an issue also. If the intent is to use a single battery, the wiring must very stiff. Four gauge at no longer than ten feet would probably be the way to go. The problem I see with single battery systems, is that, for the WFCO to work correctly, the capacity has to be high enough to absorb the full output of the converter when powered up from any previous mode. The problem arises when we look at capacity and battery size. While the Trojan J150 used during my testing works with the WFCO, it's a nonstandard size. This greatly limits the number of users that can accommodate this battery because it simply just won't fit. Doing some shopping around and finding the highest capacity battery that'll fit in the compartment is the goal. Look for other sizes and shapes of batteries than the typical group 24 and 27 batteries that are common.

My personal recommendation is to use a two battery system with these units. The wiring can be more forgiving and the converter goes into bulk mode from float, much easier than with a single battery system. Two 6 volt or two 12 volt batteries, or more, works very well with the WFCO. Most people have room for two group 24 batteries which will give them about 170 amp hour capacity. If wired in as I've stated, that should work, but it's close to the edge of working properly. Those that can fit in the taller 6 volt batteries like the T-105's, will gain 55 amp hours capacity and falls right in the "sweet spot" for operation and can get away with a little more lax wiring installation.

I believe any total battery capacity that's at least 200 amp hours or more is probably what the converter was designed for. That's just personal opinion however.

On operation:
From these tests, I can tell you this, don't expect to see your WFCO converter to go directly into Bulk mode charging at power up. First off, it just doesn't work that way. Bulk mode is not the default mode on power up! The converter does make a decision about going into Bulk mode! Second, you're not ever going to see 14.4 volts on power up no matter what! In fact, you'll not likely see that voltage for several minutes to even hours after power up and in some instances, until the batter(y/ies) reach 85% to 90% SOC or higher. Even then, you may not see 14.4 volts. You may however, see a voltage that proves the converter is in Bulk mode, like 13.8 volts. Even with a two battery system that's been lightly discharged to something like 70% or 80% SOC, you won't see 14.4 volts on power up but you might be able to confirm Bulk mode at that SOC within a few minutes after power up. This holds especially true for those that are running a bank of four, 6 volters in series/parallel or more than two, 12 volters in parallel which are deeply discharged. Being the Bulk mode charge period only runs for four hours, those with very high battery capacity (6+ batteries) may actually never even see the Bulk mode as measured with a voltmeter. This would suggest you need a higher output converter like a 60 or 80 amp model, or, possibly even parallel two converters together to gain more charge current. Just because you don't see it, doesn't mean it doesn't actually happen however. The graphs presented within this document prove without a doubt this is true. If there's enough capacity to draw the full output from the converter for more than four hours, you may never see the voltage rise high enough to even confirm Bulk mode operation.

The way to tell if the converter is in Bulk mode, is by monitoring the current output of the converter. The use of any of the popular battery monitors will tell you if your WFCO is in Bulk mode. Alternatively, the use of a shunt and separate ammeter will suffice if you want an inexpensive permanent installation. The shunt should be rated to operate continuously at a current of at least 50% over the stated current output of the converter. The ammeter should be sized likewise. If you want to know more about this, PM RJgonfshin on the RV.net forum (he just loves those ammeters). If you just want to know if it's working properly and don't require a permanent installation of a battery or current monitoring system, a clamp-on current tester can be used to verify it's operation. Sears sells one for around $50.00. In a nutshell, any current measured over the labeled rated output of the converter indicates it is in fact in Bulk mode. I would venture to state that any current output within 10% below the rated output for a sustained period of more than about 10 minutes would indicate the unit is in Bulk mode also.

YoDude, 2006