I think is related in the screen of my mobile phone, the delta value have 3 decimals, on my screen only shows 2 of them.Wonder why the cell delta shows as 0.
What was your charge voltage?
I would say put the pack into service and see if the BMS can keep the cells top balanced.
Why?Ok, so I will let them settle down, and give the final charge of 3.65*8 in series.
Can I assume after that, that they are top balanced?
I followed the previous advice of @smoothJoey and already change to 3.425.One thing I saw and forgot to mention.
Change the setup for start of balancing. You presently have it set to 3.0v. Change it to 3.4v.
Balancing in the flat portion of discharge curve will likely misbalance cells so you have a cell overvoltage shutdown problem when attempting a full charge absorb cycle
When you have a moderate amount of inverter discharge current, slight cell impedance variations and variation in battery terminals connection resistance will cause more or less voltage drop, enough to send the balancer balancing in the wrong direction.
Somewhere in the setup screens there is a balance variance setup. No benefit to set it any lower than 5 millivolts as that is about the real accuracy of BMS cell voltage determination. Setting it lower just causes balancing to thrash on and off more.
Sorry, but I don't understand this question?What is the expected in service charging voltage?
As a newbie I'm just following the experts advices: top balancing + capacity test before putting the cells at work.Time for the mad scientist part to end and put these cells to work.
100% agreeTime to cycle your battery a few times to test your efforts and then throw a Heltec 5A balancer into the mix.
I think we fuss too much about balancing to the last mV. Cell delta under 50mV is quite acceptable.
Purists , shoot me now.
You top balance in parallel, not in series.Hello,
I'm building a 16 cell (48V) 272Ah battery bank, and yesterday I started to top balancing the first 8 cells.
I'm using JKBMS 24S 2A 200A BT and two benchtop power supplies (30V10A anda 60V5A) with 15A total.
I put the cells in series and the top balance procedure started, btw the "Balance" feature of the BMS was turned on during the top balance.
After aprox 14h the BMS was triggered since "Cell Over Voltage" 3.6V was reached.
And this is what I got:
Cell initial state (V) 4h later (V)
(charging)14h later (V)
(stop charge)17h later (V)
(w/Balance:On)1 3.295 3.555 3.419 2 3.296 3.381 3.354 3 3.295 3.549 3.419 4 3.292 3.366 3.350 5 3.293 3.375 3.551 3.419 6 3.295 3.380 3.354 7 3.295 3.544 3.419 8 3.290 3.392 3.371 3.348 Delta Cell 0.006 0.017 0.189 0.071
As we can see 14h later there is a big diference between the cells voltage, but curiously the cells 1,3,5,7 are very close, and cells 2,4,6,8 also.
(the column "4h later" shows the lowest and highest voltage cells)
So, what could happen? Different SOC cells, but why exactly between pair and odd cells?
Should I leave the cells in series so the JKBMS could balance them? Should I connect them in parallel and let them balance?
Edit: add "17h later" column (the cells are settling with BMS "Balance" mode on)
Thanks
NoOk, so I will let them settle down, and give the final charge of 3.65*8 in series.
Can I assume after that, that they are top balanced?