Converter won’t charge at 14.4v

[bogen2]

I have a WFCO WF-9855 converter and it only charges at 13.7v. I assumed this was because it wasn’t a 3 stage charger, but when I checked the specs it is supposed to bulk charge at 14.4v and 55 amps. With the batteries at 50% it only runs at 13.7 at less than 20 amps. I was going to replace it with another brand but now I’m thinking there might be nothing wrong with it. I’m guessing that the problem might be that it’s too far from the batteries.

So I’m considering moving it to the front bay next to the batteries instead of replacement, which I was going to do anyway with a new one. Does anyone know if this will work? Or is this just a crappy converter? This was never a problem in the past but we’ve started to do more boondocking and it was taking so long to charge with a generator that I have been using my portable 40a charge instead.

Bob

[Country Campers]

You could easily move it to the front bay to test the theory that it will work better there, which it should. Remove the 12 v dc wires from the converter, cap with a wire nut. Unplug the unit, if it is plugged in to the back of the power center as some are. Then move to the front bay and either use your genny or an extension cord to power it and wire to the 12 v circuit in the front bay, test to see if it is different. I will guess that you will still only see about 20 or 30 amps of charge but it should go to bulk at 14.4. I am not sure what battery you have so a charge recommendation would be based on that knowledge.

If you decide to just add a new converter to the front bay leave the stock one in position and just unplug it from the power panel. What I did after that was run a 12 gauge extension cord to the front bay and wire it into a standard house outlet in a plastic box. Leaving the stock converter in place is nice if you want to revert back to the stock system it is easily done.

Brian

[howson]

bogen2

What you're seeing is the converter in absorption mode. (The three stages are bulk, absorption, and float.) See https://wfcoelectronics.com/theory-of-operation/ for a complete description of the theory of operation.

Bottom line (assuming you have a LifePO4 battery bank): if you want to speed up the charging get a replacement converter. TucsonJim and Country Campers have gone down this path.

Brian's post is here: https://gdrvowners.com/forum/operati...erter-chargers

Jim's is here: https://gdrvowners.com/forum/solar/1...born-batteries

Howard

[bogen2]

howson

My batteries are two 6 volt lead acid so I would expect that the 50a converter should be sufficient.

Bob

[TedS]

bogen2 are you concerned because your batteries are not being charged or just curious about the converter performance? What is the DC load while charging the batteries?

[bogen2]

TedS
My concern is the long recharge time. I want to bring them back to at least 80% in a couple of hours of generator time.

Bob

[Cate&Rob]

bogen2 Hi Bob,

You can't "force" a lead/acid battery to absorb a charge more quickly by applying a higher voltage. If you were to measure the charge current during the absorption phase at 13.6 V vs 14.4 V . . . you would not likely see much difference. As lead/acid batteries approach 80% SOC, power absorption rate goes way down.

I used to charge the bank of lead/acid batteries on my boat by way of a 12V alternator driven by the 120V generator. Voltage out put of the alternator was constant and I could monitor charge current. When I would start charging, the bank would absorb the full output of the alternator, nearly 100A. After an hour of generator run time (when I really wanted to shut that thing off) charge rated would be down to a painstakingly slow 20A. The alternator could put out more, but the batteries would not accept more at their higher state of charge. Charge voltage remained the same.

See the first link in howson Howard's post 3 for more explanation of this.

Rob

[ncitro]

bogen2 I agree with Rob and have seen the same thing over the years. One of the benefits of Lithium that people sometimes do not mention is how fast they take charge. If you are doing a lot of generator recharge switching to Lithium can significantly cut down on the run time. My Lion Energy batts (and most others that I know of) take their full rated charge right to 99% SOC. I have seen this play out when we have dry camped with my in laws with lead acid and I ran my generator for an hour or two and they had to run theirs for five or more. I have a 100A converter and 120A charging on my Multiplus and my bank of six takes that all the way to 99% on my shunt before falling off.

[bogen2]

Cate&Rob My goal is to shorten my charge time as much as possible. When I use my portable charger I get close to 40a charge rate that ramps down to less than 20 after an hour or two. With my current charger the most I get is about 20a and drops into the teens quickly.

Bob

[Cate&Rob]

Cate&Rob My goal is to shorten my charge time as much as possible. When I use my portable charger I get close to 40a charge rate that ramps down to less than 20 after an hour or two. With my current charger the most I get is about 20a and drops into the teens quickly.

Bob

Fair point . . . if the charger can't reach the maximum absorption rate of the significantly discharged batteries, a more powerful charger will increase amount of charge absorbed in a given time. Agreed that shortening charge time is a good goal when charging from a generator . . . less important if charging from shore power.

Rob

[Jomani]

One question I haven’t seen addressed in this thread (I may have missed it) is the age of the batteries. Has this been an issue since new or something that is getting worse?

Lead acid batteries need to be charged to 100% to avoid sulfation from damaging the batteries. It sounds like you routinely bring them back to 80% using your generator then begin the discharge process again. The difference in output between the two chargers could simply be the charging algorithm they use. If I had to guess, I would say that the converter is probably more inclined to be more conservative where the stand-alone charger is more aggressive.

Below is a quote from Wikipedia:

“Sulfation occurs in lead–acid batteries when they are subjected to insufficient charging during normal operation. It impedes recharging; sulfate deposits ultimately expand, cracking the plates and destroying the battery. Eventually, so much of the battery plate area is unable to supply current that the battery capacity is greatly reduced. In addition, the sulfate portion (of the lead sulfate) is not returned to the electrolyte as sulfuric acid. It is believed that large crystals physically block the electrolyte from entering the pores of the plates. A white coating on the plates may be visible in batteries with clear cases or after dismantling the battery. Batteries that are sulfated show a high internal resistance and can deliver only a small fraction of normal discharge current. Sulfation also affects the charging cycle, resulting in longer charging times, less efficient and incomplete charging, and higher battery temperatures.“

[howson]

Cate&Rob My goal is to shorten my charge time as much as possible. When I use my portable charger I get close to 40a charge rate that ramps down to less than 20 after an hour or two. With my current charger the most I get is about 20a and drops into the teens quickly.

Bob

Bob,
If the goal is speed, change the batteries.

Using the Trojan T-105 as an example, according to https://www.trojanbattery.com/produc...looded-battery the 20 hour capacity amp-hours rate is 225.

There's a chart at https://www.trojanbattery.com/resour...ry-maintenance that states the maximum charge rate is 13%. So 225 x .13 = 30A maximum. Given that the batteries are at 50% state of charge ( so 225 / 2 = 112.5 ), that means at least 4 hours to charge them but the reality is it will be longer since the charge rate goes way down as the batteries fill up.

As Neil mentioned, the ideal charge rate of our LifePO4 batteries is 1/2 of their rated aH, so with one battery (100aH rating) we can push 50 amps to it--right up to the point where it's almost totally full. Two batteries in parallel, we can push100 amps. Our Multiplus' can push up to 120 amps(!) when charging, so this is possible. Since I have four batteries in parallel, at the max charger setting each battery is getting 30 amps per hour from the charger PLUS the batteries will absorb from the solar panels, too. They charge fast.

The best demonstration of the difference between the rate of charge between battery types is Garrett Towne's video (which I've posted before) so if you haven't watched it, please set aside three and a half minutes to watch it -- well worth your time.

Howard