Newbie DIY Battery maker has Voltage Question

[hagensieker]

I bought these from Alibaba.

Catl Lishen 3.2v Lifepo4 202ah Lithium Batteries 3.2v Lifepo4 200ah Battery For Ess,Off Grid,Home Solar Energy - Buy Catl,3.2v Lifepo4,200ah Lifepo4 Product on Alibaba.com

Catl Lishen 3.2v Lifepo4 202ah Lithium Batteries 3.2v Lifepo4 200ah Battery For Ess,Off Grid,Home Solar Energy - Buy Catl,3.2v Lifepo4,200ah Lifepo4 Product on Alibaba.com

www.alibaba.com

I'm convinced they are not new batteries.

The Specs say normal voltage is 3.2 (12.8v) and Charging Voltage is 3.65 (14.6v).

The best charge I can squeak out is average 3.47 or so out of each cell.

After the last charging cycle my battery float was around 13.7. I disconnected PC voltage and I'm reading 13.74

They were charged by a Victron 100/30 SCC with these parameters:


Every SOC I've ever seen for LifePO4 shows 13.6 as 100% charged.

What would be your opinion of these batteries?

Also I've never done a full discharge on them. Should I do that and charge again? Would that make a difference?

My opinion of these batteries is, and please tell me if I'm correct is that they are used but still in pretty good shape.

I'm not real happy with Alibaba but thinking these are still pretty okay.

Or I've done something stupid and missed something. In which case tell me. I can take it.

 

[Steve_S]

I'm not real happy with Alibaba but thinking these are still pretty okay.

I would not blame Alibaba, they are a service provider, The VENDOR on the other hand is another matter all together. In your case it is
Changsha Deligreen Power Co., Ltd. which several have dealt with and had mixed results. I have not bought cells from them and my dealings with them was "long ago" in a different time it seems.

If you have the actual specification sheet for the specific cells it would be helpful.
are you uing a BMS ? It is possible that it is throttling the cells ?
have you tried charging the pack up witout the BMS ? If Yes, were the voltage results the same ?

 

[hagensieker]

I would not blame Alibaba, they are a service provider, The VENDOR on the other hand is another matter all together. In your case it is
Changsha Deligreen Power Co., Ltd. which several have dealt with and had mixed results. I have not bought cells from them and my dealings with them was "long ago" in a different time it seems.

If you have the actual specification sheet for the specific cells it would be helpful.
are you uing a BMS ? It is possible that it is throttling the cells ?
have you tried charging the pack up witout the BMS ? If Yes, were the voltage results the same ?

Yes, using a BMS. I'll take a look at the Params. Thanks.

 

[hagensieker]

Here's my Params. I don't see anything that would keep me from hitting 3.65 per cell I'll bypass BMS tomorrow like you mentioned.

 

[hagensieker]

It does seem to be the BMS. When I hooked my PD9130L to it without the BMS hooked up I was able to charge to 14.6 and it held for a bit after disconnecting the charger.

I think the problem lays in the cell balance. Cells 1 and 4 are higher than 2 and 3 a bit. I tried doing a Charging Balance but cell 1 always kicks the over voltage alarm and stops.

I'm currently doing a Static Balance and will see what that looks like in the AM.

 

[Craig]

Sounds like you are on right track one high cell is shutting everything down. I assume by static balance you disconnected and put them in parallel?

 

[hagensieker]

Sounds like you are on right track one high cell is shutting everything down. I assume by static balance you disconnected and put them in parallel?

Yep. I woke up this morning and the cells were balanced at 3.3v which is essentially what they showed up right out of the box with.

However when I charged them, the same thing happened. Cell 1 and 4 went to over voltage and 2 and 3 were lagging behind. However cells 2 and 3 were closer than they were before.

Is it possible this is something that takes a few cycles to iron out?

Then I observed this:

When I removed the load and applied a load for a few seconds (heat gun) the cells all dropped to 3.4 something and were all within .03 of each other.

Right now I depleted them about a 1/3rd and have them outside on a Victron SCC MPPT. Will see what happens next.

 

[hagensieker]

Hooked to Victron SCC and it went to 14.6 then went to absorption then float. Voltage is at 14v now and decreasing and cell 1 and 4 are still about .1v over 2 and 3.

I'll let it cycle a few days and see what's happening. Also maybe I'll buy a Daly BMS and eliminate the Batteryhookup.com BMS as a problem. There's no doubt the way I'm going that I'll need another BMS laying around the house here anyway.

 

[Craig]

Your cells probably have a little bit different capacity. All cells are a bit different from my tests (over 150 cells) but how much different is the question.

You should really do a capacity test of each cell at some point. while .1v is not optimal its not unheard of either. The chargery balancer default setting is to stop balancing at .075v so you really are not too far off.


In my bank I have 1 cell that is always low when its full but it is higher when near the bottom. I used to worry about it but it stays the same. So i quit obsessing. because I know it has the same capacity as others its just its energy is stored differently

 

[hagensieker]

Here's the way I'm starting to look at this. I have 2 Battleborn 100ah batteries in parallel. After bulk, absorption and float they "begin" at about 13.5 and drop sort of quick down into the 13.3 range where they stay forever. I have zero clue what the cell balance is.

The Chinese batteries I just built bulk, absorb, and float and land at 13.5. I really haven't done too much discharge tests on them but they are kind of acting the same. Also when they discharge a little they seem very balanced. It's only at the top of the charge they weird out.

Now the only difference is that I KNOW what the cell balance is. Right now my Chinese battery is at 13.5 and static balancing and showing 100% capacity.

I'm beginning to think the smart play is for me to kinda sorta ignore the cell balancing and just check it once in a while.

Still I am trying to learn and gain a bit of knowledge for the next build.

 

[Craig]

Yo think you are on right track. I'm working on some sketches to try and theorize why they get out of balance but are still ok

 

[Sojourner1]

Have you tried lowering the voltage below the point that the cells shut down from over voltage so the cells that need to come up they will. Start at 14.2 or what works for you, then add another .1 and so forth till 14.6 if that's your end goal for voltage.