Trouble charging (one cell triggers OVP at 35% charge)

[740GLE]

I’d be amazed they’d offer any “warranty advice” soon as you broke the seal to the lid to look at the cells.

 

[jameshowison]

I’d be amazed they’d offer any “warranty advice” soon as you broke the seal to the lid to look at the cells.

Jakiper has been great. They have consistently answered emails, made videos to show how to do needed service. You can see those videos on their channel. They sent a new individual cell to replace (although I'm hoping I don't need to).

I mean better that no service was needed, but they've guided people in opening the batteries, tightening connections, replacing BMS, and doing a full rebuild to replace a cell.

https://www.youtube.com/@JakiperBattery

 

[jameshowison]

Follow up to this. I re-torqued all the cells in the battery. There were quite a few that required substantial tightening (again, nothing physically lose but definitely below torque specs). I added the Nord Lock washers.

Unfortunately that has not fixed the issue, Cell 04 is still substantially dropping on load (~3.0 while all other cells show ~3.3) and high on charge (~3.5 which all other cells show ~3.3). So that confirms that this was a bad cell. I will replace it with the cell that Jakiper sent through. It's a buinch of work, though, so I don't know when I'll get around to it (took this one out of the RV).

Two things I noticed when doing the torque tightening.

1. The balance leads have insulated ring terminals. The wider flanged nuts (and the matching nord lock washers I got) are very borderline for the balance lead ring terminals to seat well. A few I looked at seemed to have had insulation squeezed under the nut. I tried to ensure that didn't happen again, but I wasn't up for trimming the insulation back with a knife while the battery was all hooked up. I've done that on a few ring terminals in the wider build, so I know that insulation can block good contact. There is a chance that this is still a problem with Cell 04 (but I doubt it, because I saw that possible issue on a few cells and the others are fine).

2. The nord lock washers are cool, but their instructions (and their help line) specific rule out the situation where you have a ring terminal between the busbar and the nut. https://www.nord-lock.com/globalass...ord-lock-original-washers--user-manual-en.pdf. I interpret the non-threaded part in these pics as the busbar, and the plain washer in red as the ring-terminal.

 

[Checkthisout]

Follow up to this. I re-torqued all the cells in the battery. There were quite a few that required substantial tightening (again, nothing physically lose but definitely below torque specs). I added the Nord Lock washers.

Unfortunately that has not fixed the issue, Cell 04 is still substantially dropping on load (~3.0 while all other cells show ~3.3) and high on charge (~3.5 which all other cells show ~3.3). So that confirms that this was a bad cell. I will replace it with the cell that Jakiper sent through. It's a buinch of work, though, so I don't know when I'll get around to it (took this one out of the RV).

Two things I noticed when doing the torque tightening.

1. The balance leads have insulated ring terminals. The wider flanged nuts (and the matching nord lock washers I got) are very borderline for the balance lead ring terminals to seat well. A few I looked at seemed to have had insulation squeezed under the nut. I tried to ensure that didn't happen again, but I wasn't up for trimming the insulation back with a knife while the battery was all hooked up. I've done that on a few ring terminals in the wider build, so I know that insulation can block good contact. There is a chance that this is still a problem with Cell 04 (but I doubt it, because I saw that possible issue on a few cells and the others are fine).

2. The nord lock washers are cool, but their instructions (and their help line) specific rule out the situation where you have a ring terminal between the busbar and the nut. https://www.nord-lock.com/globalass...ord-lock-original-washers--user-manual-en.pdf. I interpret the non-threaded part in these pics as the busbar, and the plain washer in red as the ring-terminal.View attachment 161844

View attachment 161845

That looks to be the case.

Looks like they want the washer directly on a "locked" part that is not free to rotate.

 

[Lt.Dan]

2. The nord lock washers are cool, but their instructions (and their help line) specific rule out the situation where you have a ring terminal between the busbar and the nut. https://www.nord-lock.com/globalass...ord-lock-original-washers--user-manual-en.pdf. I interpret the non-threaded part in these pics as the busbar, and the plain washer in red as the ring-terminal.

You might be able to add the ring terminal to a different place on the bus bar. Drill/tap a new hole in the middle of the bus bar to prevent the ring terminal from interfering with the lock washers.