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Here is the task. My camper has a WFCO 8945 power converter/distribution center. Now if you go to the WFCO website and read the literature it says the converter will bulk charge at 14.4 VDC, but you can not measure that with a meter because of the V/A relationship. So I put my Fluke on the lead to a severely discharged battery and it maxes output at 29 amps from the converter. Now what I want to know is first how to establish whether the converter meets its rating i.e. how can I test it?
What I am trying to figure out is how to charge my batteries faster. If I jumped to a higher rated converter could I charge my batteries faster and reduce my generator run time and fuel consumption (I can easily drop in a higher rated power board). If the battery load simply is what it is, there is no sense in changing chargers, but that doesn't jive with my experience with high end charging systems.
So I email WFCO tech support which simply said amp draw is determined by the load, all a converter does is produce voltage. Huh? Any ideas how I might proceed to answer this question? I asked for a further explanation, but whenever I have tried to deal with converter manufacturers before all they ever say it some like "we test it at the factory". I will be surprised if I hear anything further.
The amp output of the charger will be determined by the battery. The internal resistance will change as it is charged. The charger must produce a higher voltage level than the battery to get the current to flow into the battery. I'm not familiar with these chargers but I think they can be made to force a current flow regardless of load but I don't know how they can accomplish that.
You can set your meter to voltage and measure the voltage across the terminals while the battery is either idle, being charged, or in service discharging.
The amp output of the charger will be determined by the battery. The internal resistance will change as it is charged. The charger must produce a higher voltage level than the battery to get the current to flow into the battery. I'm not familiar with these chargers but I think they can be made to force a current flow regardless of load but I don't know how they can accomplish that.
You can set your meter to voltage and measure the voltage across the terminals while the battery is either idle, being charged, or in service discharging.
Turbo,
I think we are on the same page. Here is where it gets confusing. The manufacturer insists that the 14.4 VDC bulk charge can not be measured with a meter. They say this in writing and state to measure the function if you meter reads 13.6 VDC the converter is working. I guess I am dumb, but I don't see how there can be a 14.4 VDC incoming that can't be measured. However, be that as it may, how can someone actually see if the converter is capable of it's fully rating. On other converters, when I put them on a severely discharged battery I could measure their full rating and often a fair bit more in amps with my Fluke. From what I have read, if I switch to a higher rated power board, I should be able to charge my batteries more quickly. so I would like to know if this a battery issue or a converter issue.
The other thing I have noted is when hooked to my batteries, the charger does not go to 13.2 VDC "float" for two or three days despite the fact the batteries are only a year old as is the charger. I have never seen a charger take so long to go from absorption to float.
What I asked them to tell me is what test procedure can I use to demonstrate my converter will produce it's full rating. If a severely discharged battery is not an adequate load what does it take to get the charger cooking. I don't think they will answer that question because it cuts right to the heart of whether a charger is working. I guess I'll see.
Kind of interesting I was looking over WFCO's power board replacement for Li+ batteries and I see where it is only two stages, just bulk and absorpsion. There is no float stage so stays at 13.6, never drops back to 13.2 float like their other power boards. Just starting to research Li+ charging. Do all Li+ chargers work like that?
Yes, lithium basically takes bulk to 99%. They don't really care for float from what I gather. I have a battle born and love it, they really work well with solar with the fast charge times.
Just got off the phone with WFCO engineering. Really interesting discussion. The converters read the integrated system, not just the batteries and more interestingly, they do not switch over to their maximum output until the draw reaching the ratings so you will never see the converter rating until full load is reached. If I switch to a larger power board, charging will actually take longer! If I want to decrease my charging time the change to make would be to drop down a size to an 8935 rather than 8945 power board. That would be likely to see a full load condition faster and jump to max output sooner. Remember my goal here is to decrease generator run time when charging the batteries. I also asked why it takes so long before I see 13.2 float voltage and that is timed to 44 hours on before it drops
However, their Lithium power board does not read the integrated system, it reads only the batteries so I could go up a size to a 50 with that Li+ power board and the new power boards coming out designate only the batteries as the load like their Li+ board.
Now I don't claim to know how the "smart" chargers work, but it was an interesting conversation for sure!
The converter / load center / smart charger operates differently than a typical DC power supply (a voltage source). I liken the unit to a current source.
In bulk mode, the SC should deliver rated current while the the battery voltage climbs to a target of 14.4 V. Testing the battery voltage In this mode may tell you the SC is operating, but not how well. A DC clamp meter around battery + lead will well how much current is flowing into (or out of) the battery. If there are no other loads and something close to full rated current is flowing into the battery, then the SC is probably OK.
In absorption mode, the SC will vary current to maintain the 14.4 V target voltage. When the SC first transitions from bulk- to absorption mode, the charge current will be relatively high. Approaching the end of absorption mode, the battery voltage will still be 14.4 V, but charge current will be relatively low. You can measure this mode’s voltage with a meter across the SC battery terminals.
In float mode, the SC will reduce battery charging current even further to maintain the new target voltage (~13.4V?). You can also measure this mode’s voltage with a meter.
The chart below illustrates the V-A relationship for typical smart charger’s modes (aka “stages”).
That's what I thought too, but it is not true for all converters. At least for WFCO power centers like I have their manual clearly states you will never see more than 13.6 VDC on the meter even when in bulk mode at the batteries. However, what set me on my task was trying to figure out if there was a way to ramp up the incoming current to the battery to reduce charging times and thus generator run time.
Their distribution centers prioritize the needs of the camper apart from the batteries and even with a discharged battery, until the battery draw approaches the full rating, the converter never goes to full output in bulk (if hooked to a battery in isolation). Thus to get a converter to kick to high output sooner, you go with a smaller converter rather than a larger one which was my thought i.e. go with a 55 if you have a 45 to charge faster, but not the case I was told. The engineer actually did some tests to demonstrate this. Their converters also do not drop down to the 13.2 VDC until I believe he said 44 hours had passed so it is timed as I also asked why it took so long for me to see 13.2. This is regardless of battery state it will not drop sooner.
The however, however is their new line up technology not yet available except with the Li+ 50 amp power board will operate more like a battery charger and if I decide to go that direction, it will speed up the charging process, however should not be used with AGMs, which I have now. Their Li+ is also timed and only stays at 14.4 for four hours and then drops and holds at 13.6, only two stages. To get it back to 14.6, you have to disconnect and reconnect to start the 14.4 over regardless of the state of the battery at first start-up (per the website).
Now I know this may not the case with all power converters and the way I learned from Xantrax in tech school is in fact what you said. For example, Parallax's tempassure converters compensates charger output based on ambient air temperature, not battery temperature so it's charging pattern changes with the seasons, so go figure. I think the manufacturers all have their own smart boards.
Yes, I agree. I know going to Lithium is inevitable and I do want a charger that can be switched between battery types. I am not sure why WFCO is going to a Lithium on charging profile in a converter. Seems like every time I turn around I have to learn something new!
Don’t rule out excessive voltage drop as an issue.
My Progressive Dynamics converter is rated at 45 amps. The highest charging amps I measured at the batteries was less than 15 amps on a lithium pair of batteries at 30% SOC. Turns out the TC 8 AWG factory wiring from the converter located in the front of the TC to the batteries located in the rear of the TC was undersized and caused excessive voltage drop.
For the wire lengths in my TC, the wire size/current charts called for ~4 AWG wire instead of 8 AWG. I bypassed the factory wires and went slightly larger and installed a 2 AWG wire pair, and now have measured as much as 43 charging amps at the batteries.
Suggest using your meter to measure for excessive voltage drop to see if that is causing your low amp charging rate.
First change I made was to increase the wire ga even though the wire run was not long. It did not lead to any measurable change with my meter. What I posted was after direct conversation with WFCO. Progressive uses a different charging algorithm, however WFCO is in the process of changing theirs from what I understand. With a WFCO converter, to see full output or at least what it is capable of, the battery has to be severely discharged and there must be no other load. Using WFCO converters in the past on batteries in which the owner forgot to turn something off, I actually measured, the converter output exceeded it's rating.
However, I think your point is an excellent one. In my opinion, camper manufacturers consistently try to get by using the smallest or cheapest of anything often leading to marginal functionality for the end user. Very few folks would consider wire sizing, so I applaud you for your attention to detail!
