48v Jakiper with one low cell UVP

[Lukowski]

Managed to run a charging cycle on 2 out of 3 of these 1st generation Jakiper batteries that have been sitting here for over a year...
Long story short. One of them has a low cell, so the UVP fault is preventing charging to occur. It's very low, according to the bms software it's reading 248mV, while the other cells are reading ~3200mV.
This battery has never been cycled.

Using a growatt 12kW to charge through utility.
Do I need to open the case and find the low cell and charge it manually?
Can I use the bms software to override the low volt protection fault to charge and balance the cells?
I am a beginner here so any input would be appreciated and welcome.
Would rather approach this problem the right way the first time instead of doing something dumb and causing more problems or potential danger.

 

[BentleyJ]

First I would check the low cell with a multi-meter and verify the voltage is being read accurately by the BMS. If its really that low there is a very good chance the cell is damaged and cannot be recovered. LFP chemistry really doesn't like to be cycled below 2.5V.
If you have access to a bench top power supply that can charge one cell at the proper voltage, its always worth a try before declaring it DOA.

 

[Lukowski]

First I would check the low cell with a multi-meter and verify the voltage is being read accurately by the BMS. If its really that low there is a very good chance the cell is damaged and cannot be recovered. LFP chemistry really doesn't like to be cycled below 2.5V.
If you have access to a bench top power supply that can charge one cell at the proper voltage, its always worth a try before declaring it DOA.

OK, multimeter ready, can the pack be measured without removing the bars connecting the terminals or do they have to be removed?
I think my father in law has a power supply that can be utilized.

 

[BentleyJ]

Disassembly is not required. The BMS has no problem measuring voltage and balancing individual cells while the bus bars are in place. Therefore a multimeter and separate power supply can do the same thing.

 

[Lukowski]

Verified the mV of one cell is 170. Not sure how that happened. The batteries where fine when I recieved them.
Is if acceptable to release the bus bars to the pack, and remove it? Maybe the manufacturer can send me a replacement or I can find one online somewhere..

 

[BentleyJ]

Verified the mV of one cell is 170. Not sure how that happened. The batteries where fine when I recieved them.
Is if acceptable to release the bus bars to the pack, and remove it? Maybe the manufacturer can send me a replacement or I can find one online somewhere..

If the bus bars are bolted, not welded then the cell can be removed. Keep in mind that the danger involved is not so much being shocked by the relatively low DC voltage its the potential for arc flash, and spattering molten metal if a conductive wrench is dropped causing a dead short across the terminals.
Either use a composite tool or wrap electrical tape around the wrench except for the business end that fits the nut or bolt.

 

[Lukowski]

I cannot seem to locate the same size cell in terms of dimensional height(LxWxH).
What I can find is, 3.6V, 105aH, Same width, 1.5in x 5in, but the height is shorter than what I have.
Looks like my cells are 10in in height.
I have contacted manufacturer with no avail. Maybe I can pull the cell out at this point and see if that specific cell is still available.
If not, Mabye I can use the closest rated cell 3.6v 105ah and put a spacer underneath to make up for the 3 inches.
This server rack battery is rated at 51.2V at 100aH. Tried to find out if anyone has ever replaced a bad cell in their battery pack and nothing is coming up in my search results.
If most 3.6V batteries on the market are 105aH, why would a 100aH server rack battery be rated at 100aH? Do They derate the pack on purpose?

 

[Lukowski]

OK, so the battery company got back to me. They said it will be easier to charge the cell back with a "cell charger". I hardly know enough about battery chemistry to know if what they are saying is accurate or even worth the time, but it seems they are willing to send me one so Ill give it a try!