Battery charging question

[Jmarch]

Transitioning to lifepo4 battery. I understand my converter will not charge efficiently and am wondering if using a 20a ac to dc charger is ok while rv is in use?

 

[Isaac-1]

Why don't we start from the beginning, "not charge efficiently" covers a lot of territory, so let me ask, what brand and model of converter do you have now, and what size LiFePo4 battery bank are you installing, and how will you be using it. It may be that the converter you have now will work just fine for your use, and while it may not be optimal, it may be good enough, ie it may take 3 hours to fully charge your battery bank, instead of 2 hours and 12 minutes, etc.

 

[Jmarch]

battery replacement is Renogy 100a lifepo4. converter is WFCO. off grid I will be connected to 200w solar pnl. I doubt while on shore power I would barely put a dent in the battery supply heading out fully charged but if I wanted to keep fully charged using a separate charger is it possible, I may be overthinking this but dont want to cause issues

 

[HueyPilotVN]

Your convertor charger may be a little low on charging voltage but your solar might help top it off.

It would help you if you got a battery monitor that shows charging input and usage.

 

[Jmarch]

Thats where the ac to dc charger is in question, is it safe while in operation

 

[Isaac-1]

What Bill said, LifePo4 batteries have a somewhat different charge profile than Lead Acid, they don't need nearly as much voltage differential as lead acid do, but they also charge at a slightly higher voltage, and have a sharp knee in the charge voltage at over 99% SOC. Your WFCO charger would likely charge your LiFePo4 to around 98-99% SOC just fine, and if you have 200 watts of solar and park outdoors, it should easily top off that last 1-2% and allow for top balancing. In other words, because you have solar you can probably get away with the WFCO ok.

p.s. this assumes your WFCO is working correctly, some of them have a reputation for overcharging as they get old, it would be a good idea to check the charge voltage on it with a good digital multimeter.

 

[Jmarch]

What Bill said, LifePo4 batteries have a somewhat different charge profile than Lead Acid, they don't need nearly as much voltage differential as lead acid do, but they also charge at a slightly higher voltage, and have a sharp knee in the charge voltage at over 99% SOC. Your WFCO charger would likely charge your LiFePo4 to around 98-99% SOC just fine, and if you have 200 watts of solar and park outdoors, it should easily top off that last 1-2% and allow for top balancing. In other words, because you have solar you can probably get away with the WFCO ok.

But the question is if I want to use the portable charger from time to tine vs solar am I safe to do so as if connected to solar. it's a 20a ac to dc charger

 

[Contributor]

Yes it is safe, battery BMS will handle and manage how the battery accepts charge.

 

[Isaac-1]

Sure use the 20 amp portable charger, use the WFCO converter (which I assume is larger than 20 amps), use the Solar, they all interchange just fine, though the WFCO MAY not fully top them off due to the higher peak charge voltage needed to get that last 1-2% into LiFePo4 batteries, it should still easily get them to between 95-99% SOC.

 

[Jmarch]

Thanks everybody, cheers

 

[Mark_K5LXP]

What "20a" charger are we talking about? Unless it is one with a lithium profile it may not do any more for you than the converter and take longer to do it. The battery BMS is there for protection, not charge regulation. What you hook up to charge any battery matters, at a minimum it would be something spec'd for the purpose or measured and verified.

Mark B.
Albuquerque, NM

 

[Contributor]

The BMS will control and balance the charge to the individual cells that make up the battery and will see to it that it is charged up correctly. The BMS requires the right charging voltage to do that. A charger that does not provide high enough voltage will hinder the BMS from doing it's job.

 

[Contributor]

From BattleBorn Batteries

 

[Isaac-1]

The BMS will control and balance the charge to the individual cells that make up the battery and will see to it that it is charged up correctly. The BMS requires the right charging voltage to do that. A charger that does not provide high enough voltage will hinder the BMS from doing it's job.

Correct, however he also has 200 watts worth of solar panels, that should easily handle the 1-2% topping charge needed to put the batteries into top balancing. Note Top balancing is not needed every charge cycle, a good rule of thumb though is to fully charge and top balance at least every 10 charge cycles.

 

[garyb1st]

We have 210 Ahs or lithium and a WFCO converter. While newer WFCO converters may handle the charge better, ours usually thinks our batteries are full. Our lithium batteries are usually over 13v. Consequently I rarely see a charge of more than a few percentage points going in. I haven't figured out why but from time to time, our WFCO converter will charge at a rate of about 20 amps. But as I say, I'm not sure what triggers that higher rate.

The only time our batteries become fully charged is when we're on the road. I've seen charge rates as high as 70 amps an hour at highway speeds. Also, our 2000 watts of solar will charge the batteries at up to 10 or 11 Ahs during peak sun. But then our 12 volt refrigerator uses a big chunk of that mid-day. There are options available for better charging, but so far none are without some limitations.