2P/16s back to 16s X 2

[Skypower]

I’ve been running of 6 months with a 2P configuration with great success except for the 300 Daly’s current sense has gone nuts. It can swing 2X actual current and back again(see screen grab). This has lead me to adjust the bms’s settings higher than I like since it wants to trigger a false over current and shuts down the inverters. There’s software to fix it but not good one for the 16s bms. The software I found for 16 looks flaky and may kill the thing with my luck, leaving me dead in the water. So I’m considering retiring all the 2P jumpers and going back to the #2 diagonal jumpers and having two batteries with two JK bms’s 2amp balance 200amp load(ordered,due 9/9/22). Cells are CATL 305ah Heltec retired now with Neey balancer(to be retired also).That changing around makes me glad I didn’t spend all the time straightening all the spaghetti lol.
But hear’s the catch. The cells have been compressed with 550 lbs of force (10psi) and a .040” silicone spacer between them. The spring maintains the force during minor cell expansion and contraction. The cells were reasonably flat on the sides and all looked and still look close together. In order to reconfigure the cells, I’ll have to release the clamping pressure (at low SOC) and rotate half the cells. So my question is, do you think it’s safe and not harmful to molest the cells?

 

[sunshine_eggo]

So my question is, do you think it’s safe and not harmful to molest the cells?

If it's not, something is already wrong.

 

[Skypower]

I think you’re right, but I know there’s always going to be some subtle changes to the “jelly rolls” as the sides make new friends Just don’t know how tough these things are.

 

[fafrd]

I’ve been running of 6 months with a 2P configuration with great success except for the 300 Daly’s current sense has gone nuts. It can swing 2X actual current and back again(see screen grab). This has lead me to adjust the bms’s settings higher than I like since it wants to trigger a false over current and shuts down the inverters. There’s software to fix it but not good one for the 16s bms. The software I found for 16 looks flaky and may kill the thing with my luck, leaving me dead in the water. So I’m considering retiring all the 2P jumpers and going back to the #2 diagonal jumpers and having two batteries with two JK bms’s 2amp balance 200amp load(ordered,due 9/9/22). Cells are CATL 305ah Heltec retired now with Neey balancer(to be retired also).That changing around makes me glad I didn’t spend all the time straightening all the spaghetti lol.
But hear’s the catch. The cells have been compressed with 550 lbs of force (10psi) and a .040” silicone spacer between them. The spring maintains the force during minor cell expansion and contraction. The cells were reasonably flat on the sides and all looked and still look close together. In order to reconfigure the cells, I’ll have to release the clamping pressure (at low SOC) and rotate half the cells. So my question is, do you think it’s safe and not harmful to molest the cells?

I’m using a 2P8S configuration of 280Ah cells and would appreciate to understand in greater detail the issue that caused you to switch to 8S2P (two 8S1P batteries).

My BMS just monitors cell voltage so what ‘currents’ was your Daly BMS monitoring / measuring?

 

[Skypower]

5000 watts when actually was 2000. What really got my attention was seeing it in Solar Assistant then watching the Daly app more closely to confirm.
The bms had also shut my entire system down due to a false over current. I was able to avoid it by setting the value higher in the bms. Yup, had to dilly dally, lol.

 

[Skypower]

I’m using a 2P8S configuration of 280Ah cells and would appreciate to understand in greater detail the issue that caused you to switch to 8S2P (two 8S1P batteries).

My BMS just monitors cell voltage so what ‘currents’ was your Daly BMS monitoring / measuring?

2P has nothing to do with it. You should be fine. My bad bms. I went to two jk’s for more current. The Daly300 was fine for 200 amps all day without a sweat, but I wouldn’t do that to a JK.

 

[fafrd]

2P has nothing to do with it. You should be fine. My bad bms. I went to two jk’s for more current. The Daly300 was fine for 200 amps all day without a sweat, but I wouldn’t do that to a JK.

OK, so you went from 2P8S to 2x1P8S because your BMS was mistakenly detecting overcurrent and shutting down, but with 2 smaller BMSs from another supplier, you are no longer having that issue…

I’ve got a Heltec BMS which I believe is similar to or even identical to the JK BMS.

I’m general, everything has been running fine but in several instances I have found my SCC in a fault condition which I believe has been the result of a BMS shutdown.

I’ve isolated the fault to feign caused by motor loads such as the washing machine when the battery is largely discharged but not yet at low voltage cutoff.

I’d been trying to track down a cause for this occassional fault based on a motor-induced voltage spike but had forgotten about the overcurrent shutdown…

Having the inverter shut off at a higher voltage further from the low SOC knee avoids the issue, but I’m still interested to understand the causes of this strange BMS fault and was wondering whether a 2P8S battery configuration could have something to do with it…

 

[Skypower]

I’ve got a good chance of getting a surge or back emf so I installed two identical surge protectors. One on the grid/generators source side and the other on the distribution side breaker panel. I don’t think any surge could get to the bms. I think a lot of other things would have been pickled before that. Daly doesn’t have the best rep around hear. Yes, you could very well JK-Heltec badged bms they are known for tagging their name on stuff and I think I had seen it.