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In case it helps anyone in the future, patience was the key. Thanks for the intel.

I measured the IRs of the potentially problematic cells and they look fine (and similar to the other cells). I also converted the pack to 2p8s using cells from blocks 6-8 above as well as some others. All cells were connected only by busbars. I didn't see the same behavior. For some reason the...

I switched cell blocks 7 and 8 and find the same problem. I'm assuming that this would go away if it was caused by a cell with bad IR.

It's the 8 lead version of the same JKBMS using it's owning harness/connector. Interestingly, the problem is almost gone when using the PSU (at 10A) but still exists when charging with the inverter (at 50A). Not sure what else to do/try here.

Interesting, I just switched cell blocks 7 and 8 to see if the fluctuations persist on block 7 or switches to block 8. Unfortunately it's too cold to charge them where I live - will try again tomorrow.

Hahah, TIL ;) Interesting I'm curious as to why if you have any thoughts. Unfortunately the closest I can get the two boxes is ~2ft. I just observed the same behavior with a 2 ft cable: What is max balancing? I'm not finding a defintion. Btw, thanks for all the intel and help...

It's my first time using a benchtop PSU and it was offgassing some pretty noxious stuff at the beginning. I'm guessing rosin heating up? At any rate it spooked me a bit so I've dialed down the current several times. Yeah I've seen it - maybe I'm misunderstanding something though. I've been...

Yep, though I had been charging it at 50 amps a few minutes beforehand Ahh, I turned off balancing so I could isolate a charge source. Why would balancing make a difference in terms of the fluctuations?

Exactly - the jumps are 20-30mV. Update: I trimmed back some of the rubber on my 7-8 connection and it looks like the problem improved (but not entirely) for the 8 cell block. I'm still getting the problem with the 7 cell block (which has always been the chief offender). As mentioned the...

Last week I looked at the voltage and then compared to the voltage after charging via the alternator (12.8 or 12.9). Tonight I just looked at the voltage of the individual batteries to see that they were not working.

I've noticed that when charging/discharging my eve cells (24 304Ahs in 3p8s), some of my cell blocks have much higher voltage fluctuations according to the bms. It seems to be the furthest blocks from the BMS that have this issue. For example, I see fluctuations of 3.23V to 3.251V in the 8th...

Unfortunately it was 62 F (16.5 C) today when I was testing and the batteries weren't working. I can take them out and bring them inside if you thin it will make a difference - they are a bit of a pain to get out of their frame which is why I haven't done so already.

I have been pre-charging some EVE cells in a 2p8s setup with this power supply: https://www.amazon.com/dp/B08DJ1FDXV?psc=1&ref=ppx_yo2ov_dt_b_product_details and a JK BMS (to prevent over charging any of the 8 pairs). Unfortunately at the upper ends of the voltage spectrum (~27V) the batteries...

Due to space constraints I need to split my battery cells into two different compartments. I have 24 cells in a 3p8s configuration with the #7-8 cell blocks in a different place than #1-6. They are connected via ~10ft of 4/0 awg copper cable. It's resistance (as measured by charging at 50A) is...

Interesting - is that iteration something that would take longer than a couple minutes? The resistances are anywhere between 52 and 62 milliohms:

Okay, so just to make sure these per cell block voltage swings of (0.02-0.03V) are not typical?

I just received 24 304 Ah Eve cells and need to pre charge them before top balancing. I have two questions about the document that seems to be standard on this forum for DIY balancing: https://diysolarforum.com/resources/top-balancing-lifepo4-cells-using-a-low-cost-benchtop-power-supply.65/...

I have 2 206 Ah SOK batteries that I installed (wired in parallel) in my campervan last week. At first the electrical system was working flawlessly - I hooked up a victron inverter, a sterling b2b charger, and numerous outlets. All working. I changed a few things and at some point everything...

I would understand 0.025V voltage drop, but the readings are actually fluctuating by 0.02-0.03V e.g. the 7th cell block reading bounces from 3.360V to 3.386V over the course of a couple seconds (as seen on the jkbms app). Space is quite tight (this is going in a campervan) and I can't quite fit...

Yes it did go down to 0C. Could this have caused the 9V one as well? These batteries do have a "Low Temperature Charging Cut-off" but I don't see a way to reset it. Shouldn't the battery function normally once temperatures warm up again? @acdoctor Any advice on how to proceed if this is the case?

Yes, it's fluctuating 0.02-0.03V. I actually bought a backup BMS in case anything goes wrong when I'm on the road (this is being installed in a campervan). I just hooked it up and tested it (different balance leads from BMS, same busbar connections across cells). I'm seeing the same types of...

Oh boy, now I'm nervous about the physical quality of received cells. Amy seemed pretty straightforward and I know a lot of people on this forum have gone through her so I guess fingers crossed until they arrived. Thanks for the intel.

Interesting - any suggestions for a bms? I think the jkbms does compensate for resistance of balance leads but why does the resistance of the interconnection leads matter? Why would it cause voltage fluctuations?

Hahah, I had no idea that's how it worked. Hoping they clear soon - sounds like a game of wait and see.

Update: It's now been over 3 months since I ordered the cells (on 07/07/2023) and I'm still told they are sitting in customs. Cautionary tale for anyone ordering from China.

Great thanks for the info. I will give this a shot. I have disallowed discharge in the BMS so hopefully that would also stop any backfeeding. Is there a reason I can't start with a low current and dial it up? E.g. follow your directions above but substitute the following steps: 2) Set the...

I have a weird space to install my battery in (around the wheel well of a van). I am upgrading from off-the-shelf batteries to 280aH DIY LiFePO4 eve cells in a 3p8s setup. Because the space I'm putting them in is not a rectangular prism I was thinking I would use welding cable to connect...

~10ft of 4/0 awg copper cable. It's resistance (as measured by charging at 50A) is ~0.5 milliohm which is consistent with online calculators. I understand why that would cause a voltage drop, but am confused by why it would cause voltage fluctuations.

@acdoctor thanks for the advice The batteries do not have internal heat Shore power and b2b is capable of 60 amps (using 4 AWG cables) are the only permanently installed mode of charging, but I can hook up a car charger to the batteries at low amperage (2 amps) I have not been actively...

@Diysolar123 Unfortunately I'm not sure where to find the BMS specs outside of this page: https://www.sokbattery.com/products/12v-206ah-lifepo4-lithium-iron-phosphate-battery-pack