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I messed up and discharged my LiFePO4 3.2V down to almost 0

The_Geek

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Mar 25, 2020
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I won't go through the whole story. I will leave it at "I thought everything was disconnected, I left my project and came back 3 months later and the batteries are at .3v"

They were new. 8 of them in a 24v serial configuration.

So.. any sage advice on how to bring them back to a working order??

Thanks

(they are Fortune 100Ah Lithium Battery LiFePO4 3.2V)
 
Did the BMS fail to cut off the discharge?

Charge them back up and see how they respond. They need to be charged no matter what. Might as well get started on that.
 
You need to parallel and trickle charge them very very slowly @ 1A or so over a couple weeks. If they come back at all you will have less capacity than you had before - only time will tell how much less capacity.

If you do get them to accept a charge let them sit and see if they have become high self-discharge cells. It can happen from prolonged over-discharge because of dendrite growth.

A youtuber named David Poz has recovered several batteries that came out of vehicles this way but I don't know if I'd ever trust them again for a critical system.
 
I’ve heard people say the quicker you get them charged up over 2.5 the better, but I have never seen any documentation on how. Is there any lab documentation on this process?
 
I’ve heard people say the quicker you get them charged up over 2.5 the better

We discussed this in another thread a month back. The faster you get them above 2.5V, the better. Every hour spent below 2.0V causes corrosion of the current collectors, and damage to the SEI layer.

From 2.5V just charge at a sane rate that lets you monitor them. There is a chance the cells will recover with nominal capacity. If one cell starts going wonky, slow the charge down, or individually charge that cell. If you can't monitor them, stop the charge.

If the cells have been below 1V for more than a week or two, you could see capacity loss at 15-35%. Once it gets near 30%, and stays there for a couple of cycles, the cells are probably done.
 
Every hour spent below 2.0V causes corrosion of the current collectors, and damage to the SEI layer.

Do you have a link to this info please? I haven’t got much information on cathode damage in my notes.
 
Do you have a link to this info please? I haven’t got much information on cathode damage in my notes.
I'll try and dig it up, it's on my home PC. I attached in a thread about min discharge voltage. The study related to low SOC damage and ideal air shipping voltage. I was surprised at how slow the damage was until it got below 1V.
 
Here is the research.


Thread
 
Thanks, much appreciated :)

I know there is a lot of work still being done on improving the chemistry of the anode to prevent lithium plating. I haven’t seen much research into the prevention of copper plating.

Pretty much all the life decreasing factors of these cells seem to relate back to plating of the anode. Timeframe that cells are able to be held at low voltages (for transport/bottom balancing), or high voltages (fully charged floating or top balancing) vs cell degradation seem to be up for conjecture between different studies.
 
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Well.... one step forward and 2 steps back. I am still not sure how they were discharged to that level (the BMS was plugged in but not setup, that might have had something to do with it)...

So I seperated the batteries and realizing there was never going to be enough charge in them to kick on the BMS (if it sees that low a voltage its going to cut out) I charged each battery for about 45 mins at 3.2v / .5 amps connected directly to a powersupply. Once they each held a charge or 3.2+ volts I put the BMS back it and set it up. I reset the power supply to 5a /30v and plugged it into the solar charger and set the solar charger back up (it had no settings in it either).

NOW... I seem to have BMS problems. I have an ant 16s 100a bms. I could talk to it via blue tooth. After things has settled for about a week I put a load on it now the BMS won't light up. No LEDs, no.. nothing.. I have disconnected it and re connected it multiple times, tried to short it out, I even put a 18650 battery across what are supposed to be the other set of power leads and nothing. Can anyone tell me how to reset an ANT bms? (I have a seperate set of wires to go to a charge meter and it still says 23.x volts, and the meter says each cell is at 3.33v (give or take a little).
 
Its possible the BMS failed which drew down your battery to begin with.

To power on some BMS needs to see an voltage on the output of a certain amount.

45 minutes at 1/2 amp got you to 3.2V? It should take longer than that.
 
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