Correct voltage charge for Lithium

[BajaMatt]

Hi there, I have a pair of Lithium Iron Phosphate batteries wired in parallel in my camper. I am attempting to keep them charged via my 100 watt solar panel w/controller. I have the panel set to 14.4V, but I am unable to charge the batteries above 13.0V. There is no (obvious) additional solar controller in the camper that would hinder the full voltage charge - is there another element "in the way" of the batteries charging to full 14.4V?

 

[MisterSandals]

What solar charge controller?

is there another element "in the way" of the batteries charging to full 14.4V?

Yes, the BMSs.

 

[hwse]

It is very possible that you just are not getting enough from your 100w solar to fill up the battery. plug it into a 110v charger and see if it will fill up. 200Ah of LFP with only 100w max solar is pretty light if you have any regular loads.

 

[BajaMatt]

It is very possible that you just are not getting enough from your 100w solar to fill up the battery. plug it into a 110v charger and see if it will fill up. 200Ah of LFP with only 100w max solar is pretty light if you have any regular loads.

Is it possible the existing battery separator is the problem?

 

[BajaMatt]

What solar charge controller?

Yes, the BMSs.

What's a BMS?

 

[MisterSandals]

What's a BMS?

Battery management system
Lithium batteries typically are build with a BMS that monitors each of the cells voltage and acts as a cutoff switch to protect the battery from damage from too high or too low voltage.
There are other protections too such as over current and some have temperature protection.

In your case, its possible that one cell is reaching the typical 3.65V cutoff, this causing battery shut down.

I think @hwse is more likely on track with his suspicion that 100W of solar is not enough to charge your batteries.

But its not clear if the charging stops, never completes or if you also have this problem when charging from shore power.

 

[BajaMatt]

Battery management system
Lithium batteries typically are build with a BMS that monitors each of the cells voltage and acts as a cutoff switch to protect the battery from damage from too high or too low voltage.
There are other protections too such as over current and some have temperature protection.

In your case, its possible that one cell is reaching the typical 3.65V cutoff, this causing battery shut down.

I think @hwse is more likely on track with his suspicion that 100W of solar is not enough to charge your batteries.

But its not clear if the charging stops, never completes or if you also have this problem when charging from shore power.

I've successfully charged the batteries with this panel when I remove the camper from the equation and go panel>alligator clips>battery. They read out 14.4V and Full. My guess is the current battery separator is set to/capable of 13.0V and it's the bottleneck.

 

[MisterSandals]

and go panel>alligator clips>battery.

Never recommended but it seems to rule out the BMS and panel size being a problem.

What SCC? What are SCC settings?

 

[MisterSandals]

Is it possible the existing battery separator is the problem?

What battery separator? How are your batteries wired in parallel with a battery separator?

 

[Solarcabin Channel]

What type of controller and can it be set for LI batteries?

Are the batteries same brand and Ah?

How many hours of sunshine and what amps is your panel out put?

Do you have any load on the batteries while charging? Turn them all off.

 

[BajaMatt]

I figured it out. I'm not separated from the truck battery, so the entire system is stuck at "lead acid level" until I can get a DC to DC charger in and separate it from the solar system completely.

 

[justoneguy]

Not yet mentioned,
is 3,33 volts per cell 13 volts for the pack,
is right at the charging knee.
it could be as little as about 25% charged,
or it could be 75% charged.
I've seen people think their system wasn't working correctly.
It takes a while to get past that 3.3

 

[MisterSandals]

I figured it out. I'm not separated from the truck battery, so the entire system is stuck at "lead acid level" until I can get a DC to DC charger in and separate it from the solar system completely.

That doesn't make any sense. There is no "stuck" in electricity.

Your charge controller will continue to apply charge to your LiFePO4 battery(s?) and truck battery to the voltage in which it is programmed.

If your truck battery is hard wired to your LiFePO4 house battery(s?), then that needs to be addressed asap too.

 

[featherlite]

MisterSandals,

Your mind respecting solar stuff is like a steel trap!