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OH NO!!?? Have I killed my LifePO4 batteries?

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Daz

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Jul 3, 2020
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I have a self built system what uses 16x LifePO4 cells in 2x8 12v configuration. (Build guided by Will's wonderful channel).

The van broke down and sat at a garage for over 2 months. A good period of that time, it was indoors and obviously there was no solar charging happening. A small fridge drained the batteries 'completely' (the BMS has a low cut-off protection?) - and it's not clear how long they were in that state.

I've plugged in the charger (Intel-power PD145AL ) and after 16 hours the batteries have only come up to around 5%!

I have the XiaoxiangBMS app (came with BMS) and I wonder if I should do some kind of reset or something to try and get them going - or what other method can be used to check and charge them?
 
How much current does the plug-in charger provide?

You mention a 2x8 12v build, but what is the size of the cells? 20 AH? 40 AH? 280 AH?

Did the BMS cut off at the correct 'low voltage'?
 
What's the current from the charger reading, clamp meter etc if it doesn't have a display showing actual amps flowing. How many amp hours of battery do you have there, ie cell amp hour x 2.

Google says the charger can do 45A but that doesn't mean 45A is actually flowing of course. Without blinking sideways at the specs it could be a smart charger that is lifting the battery gently since it was fully discharged and once it reaches a certain threshold then it opens the tap.
 
What was the battery voltage before you started charging?
Did the bms trip?
Did the bms app show battery status before charging?
How bout since it started charging?
 
The charger should provide 45A. When I first plugged it in, it immediately showed 42.xx so I happily left it overnight.

The batteries are 100Ah fortune. it is a 12V set up, with 2 batteries made of 4 'pairs' each. Total is 400Ah.

I don't know if they cut of at the correct low voltage. I wasn't there. How can I review the settings and confirm if it worked?

It's charging at 0.048 (+/-) and the BMS app says they are at 3%. Monitor says 12.31V and 13.5%.

Victron charger has blue Bulk light on. (There's no sun here now. Dark and raining).
 
The batteries were basically 100% when the van was parked.

"Did the bms app show battery status before charging?" If you mean before this issue, yes - everything seemed to be working perfectly before this period with drain and no charge.
 
I don't know if the BMS tripped during the drain. I did "turn the batteries on" - but there was no clear indication that they were off.
 
gnubie - let's hope that you're right about the charger bringing them back gently. I wonder how long one should allow for that to take place?

Can PO4's die from too low of a drain?
 
Daz said:
How can I review the settings and confirm if it worked?
Click to expand...
Your bms is smart and usually has a bluetooth connection that you can manage via a smartapp on your smartphone.
I wanted to know the voltage of the batteries and status of the bms when you picked up the van and noticed the batteries were dead.
 
If the Bluetooth App on the BMS was still working .... I doubt the batteries were low enough to cause harm. It wouldn't be good to leave them that way for a long time though.
 
The BMS app said the batteries were at 0% and maybe 11.78 (?) if I recall correctly.
 
Well Bob, I wan't in control of the situation, as the garage where my motor was being repaired was nearly 2 hours from here... I suspect it did sit for a fair time.

It's also possible that they drained and things shut down (?) the first time it was indoors, and that shut down would theoretically block charging when it was taken back outside. It may have been as long as 6 weeks like that.

How will I be fine? Just leave it on the charger and wait?
 
I don't think that's long enough to cause a problem .... I would be more careful and totally disconnect if you have to store in the future.
 
Yeah, I was so upset at the break down ($12,000), that I didn't think about the potential issue of them having it indoors so long.
 
Daz said:
Yeah, I was so upset at the break down ($12,000), that I didn't think about the potential issue of them having it indoors so long.
Click to expand...
Wow .... Seems like they could replace the entire power train for less than that.

It does seem like the % should be greater than that after 16 hours, but it seems to be taking a charge unless you have another load somewhere that is sucking off the charger power. Gonna have to sweat and wait.
 
Your batteries should have been charged in approximately 10 hours.
10 volts is dead empty so your batteries should have been appropriately 90% discharged when you got the van back.
Something doesn't add up.
 
I just installed in my RV those same batteries but did it in a 4S4P configuration with a single 200A BMS. I have to wonder (no claim to be an expert) when you assembled yours you made 2 2S4P packs. Did you use 2 BMS or one? You had to jumper the parallel cells if only one BMS. To your problem, I would check the voltage of each cell pair of each pack and see how well they are matched. Your pack since it went dead or very low SOC may be very unequal such that the BMS is shutting down??
 
rfguy said:
I just installed in my RV those same batteries but did it in a 4S4P configuration with a single 200A BMS. I have to wonder (no claim to be an expert) when you assembled yours you made 2 2S4P packs. Did you use 2 BMS or one? You had to jumper the parallel cells if only one BMS. To your problem, I would check the voltage of each cell pair of each pack and see how well they are matched. Your pack since it went dead or very low SOC may be very unequal such that the BMS is shutting down??
Click to expand...
Correction above I meant instead of 2S4P really needed to say 4S2P. sorry
 
Checking cell pack / cell voltages is definitely a good idea though. That'd at least highlight a problem with the voltage of one of them going high and tripping the BMS, despite the overall low SOC of the battery.
 
My setup uses 2x 125A BMS, one on each 2S4P block. It's been another 16 hours on the 45A charger and the charging rate is up to 4.9A. That's a big improvement from the earlier 0.04x charging rate!

If it's in a safe rebuilding mode, is that controlled by the BMS or the charger I wonder?

The app is reading:
Bank 1: 3% / 12.47V / cells from 3.107 - 3.126
Bank 2: 4% / 12.47V / cells from 3.096 - 3.138

I guess the plan for now is leave it as is and see if the charging rate increases as they get closer to or over 10%.

It's 10am, the rain clouds are gone and it looks like a partially cloudy day. Who knows how some solar charging might affect things....

Cautiously optimistic.
 
I just noticed that the BMS app has a toggle in the settings. "Charging port on when battery off" - yes or no.

Any informed advice on switching this on? Would it interfere with overcharge protection?
 
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