Below zero temp storage, SOK batteries charge issues

[Lez_go]

I have three 206AH SOK batteries wired in series. I haven't been working on my build, so I turned the power system off as it started to get cold. I wasn't charging, batteries were at about 13.2 V when I turned everything off as it was too cold to charge. They sat for about a month, temps in MI got very cold, below zero a few days. I decided to remove the batteries, but wanted to charge them fully before I did so.

Had a warm day and turned heat on in the van and got the inside temp up to 68° F. As soon as I turned the charger on, something was off. The battery monitor was jumping voltages all over. I turned it off. Disconnected the batteries and brought them inside. Tried to charge them individually, and now none of them will charge above 13.54V. They work, before I removed them. They were powering lights just fine. Just won't charge.

What do I need to do to diagnose the issue? Should I disconnect the BMS and individual cells and try to charge them individually to see if any of the cells are damaged?

 

[jberger]

How long have you left them inside and what is their temp?

Are you sure your charger is ok? (I just found my automobile charger was dead over the weekend, after thinking it was the battery. . . )

 

[time2roll]

Ok so it may take 24+ hours at 68 for the SOK to get back up to operating temperature. Keep the heat on and try again tomorrow.

 

[Dzl]

I decided to remove the batteries, but wanted to charge them fully before I did so.

If I understand what you are saying above, this is not a recommended practice with LiFePO4.

LiFePO4 batteries should be stored at an intermediate state of charge, most manufacturer recommendations I've seen are ~30-50% or ~30-60%. The two best things you can do for battery longevity/health when storing lifepo4 long term are (1) don't store them in the heat, especially extreme heat (2) don't store them at or near 100% SOC.

I know this doesn't answer your question, but it seemed relevant, I hope you resolve the issues you are currently experiencing.

 

[Lez_go]

How long have you left them inside and what is their temp?

Are you sure your charger is ok? (I just found my automobile charger was dead over the weekend, after thinking it was the battery. . . )

They've been inside for several days. And the charger in my rig was a victron multiplus hooked up to shore power. Inside I'm using a brand new 7a victron smart charger. I know its a small charger and will charge slowly for the size of the batteries, but I tried them each individually and they all stopped for more than an hour at 13.5V. The default Lithium settings on the charger should bring them to 14.2.

 

[Lez_go]

If I understand what you are saying above, this is not a recommended practice with LiFePO4.

LiFePO4 batteries should be stored at an intermediate state of charge, most manufacturer recommendations I've seen are ~30-50% or ~30-60%. The two best things you can do for battery longevity/health when storing lifepo4 long term are (1) don't store them in the heat, especially extreme heat (2) don't store them at or near 100% SOC.

I know this doesn't answer your question, but it seemed relevant, I hope you resolve the issues you are currently experiencing.

That's very good to know, thanks.

 

[time2roll]

An hour? Could well be normal for a 7 amp charger. I would let it continue overnight.

 

[RVLiFe]

They've been inside for several days. And the charger in my rig was a victron multiplus hooked up to shore power. Inside I'm using a brand new 7a victron smart charger. I know its a small charger and will charge slowly for the size of the batteries, but I tried them each individually and they all stopped for more than an hour at 13.5V. The default Lithium settings on the charger should bring them to 14.2.

It's interesting how the story has changed a little in this latest post. You now admit that you are using a completely different charger that only outputs 7Amps. I think your batteries are completely fine. Just let the charger do its job. 206/7= 29.42. That's 29 hours my friend to charge. NOT one hour at 13.45V. You aren't going to see a higher voltage. Please look at the graph I have attached to this post. A battery staying at 13.6V while being charged is completely normal. Once the battery gets nearly full and hits the knee, you will then see the voltage finally go up. Let it charge, let it charge.

 

[Lez_go]

It's interesting how the story has changed a little in this latest post. You now admit that you are using a completely different charger that only outputs 7Amps. I think your batteries are completely fine. Just let the charger do its job. 206/7= 29.42. That's 29 hours my friend to charge. NOT one hour at 13.45V. You aren't going to see a higher voltage. Please look at the graph I have attached to this post. A battery staying at 13.6V while being charged is completely normal. Once the battery gets nearly full and hits the knee, you will then see the voltage finally go up. Let it charge, let it charge.

Thanks for the info I didn't know that. Also I never changed my story, just added more info. There's no need for the accusatory verbiage, that doesn't make people feel good about asking for help. This forum is for DIYers of all skill and knowledge levels. I watched the voltage steadily go up and then stall for MORE than an hour, I think it was about 2 hrs or so. I was worried that I ruined 3 grand worth of batteries. Glad to know I overreacted and just needed to be patient.

 

[RVLiFe]

I apologize, I didn't mean for you to take it personal. I should not have posted it that way. I was just trying to say that there was additional information that wasn't included in your first post that changes the narrative of the issue. Thank you for providing the additional information. Yes. I don't think you should be alarmed. If you have a volt meter, you should be able to connect them to your charger and see that they are putting out the correct voltage(disconnected from the battery), It's just going to take time for the battery to take a full charge and raise the batteries voltage to that of the charger. Right now your battery is taking in a constant current of 7 Amps. Eventually, It should take in a constant Voltage of 14.4 or what ever you have the charger set to and maintain that. Then the current will drop until the charger says that it's full. Looks like you have a decent charger even though it will take a while. Please keep us posted as to your findings.

What is this Bulk, Absorption, Float, Constant Current, Constant Voltage stuff anyway? An explanation.

I wrote this in another thread and I thought it'd be useful in it's own thread instead buried 4 pages down. You've might have read me talk about using off-the-shelf CC power supplies to charge cells. The same logic applies to every charger. Lets step through each phase of a charge cycle and...

diysolarforum.com

 

[Lez_go]

Welp, turns out I worried for no reason. All three batteries fully charged and holding their voltage. Thanks for the input everyone.