I believe that is the issue I have with my batteries. When my system was installed, I think the installer installed repaired batteries. They are supposed to be 48 v 100 ah, 15s batteries. A that stage there was no software to read the bms. I resently got the software. I have 2 narada 100ah batteries connected in parallel. The bms shows the capacities as 56.3Ah and 53.8 Ah. My max voltage I can charge them is 51.7v. If i go to 51.9v, 2 cells voltage goes over 3.65v, while some cells is between 3.2v and 3.5v. Today i switched the smaller battery of, and charged the bigger capacity one to about 52.3v. If i go higher, the 2 cells go over 3.65v while others is in the 3.3v and 3.4v range. My next step is to strip them and test each cell to see what is their capacties.
15S battery charging issues. Different capacity cells?
- Thread starter Oros
- Start date
Are you sure you have a 15S pack? With LIFEPO4 15S would max out at 54.75, but a fully charged setup under normal operation should be in the 51V range. 3.4V per cell or 51V would be the norm float charging to reach 100%
If you have cells out of balance in the pack, then yeah, the BMS will cut you off early on a charge…
It sucks when a packaged battery ships out of balance, but if you set the charging to 51.0 V, and let them charge with no load, the tiny BMS balancing might get them to correct balance eventually.
My batteries capacity's has dropped, SOH is still at 100%. Cells was unbalanced. I balanced my cells to +- 3.6v. My batteries capacity is supposed to be 100Ah. Now reading 53.8 Ah. I do not believe there is faulty cells. How do I get the bms to re-calculate the capacity? When I charge the battery, as soon as it reach the 53.8Ah capacity, it stops charging. It is Narada 48v 100Ah 15s batteries.
DIYrich
Solar Wizard
Charge to 54.0v (3.60v per cell). The bms should reset.
DIYrich
Solar Wizard
Then your cells are not balanced. Start at 52.5v (3.50v per cell). Hold for a few hours to give cells time to be balanced by the bms. Increase 0.50v to 53.0. Repeat until you reach and hold 54.0v. Note at what voltage the bms resets soc. That is where you need to charge on a regular basis.
So I installed the balacers. Fantastic. Never have I seen the cells so balanced!! The problem is that the bms's did not reset the Ah. The batteries is at 54.4v. On one battery all cells is above 3.6v, and on the other only 1 cell is sitting at 3.54v. Just waiting for the balancer to do its job.
Another interesting thing, last night I charged them using utility, but the stopped charging at 52v when they reached the bms stated capacity. Today using solar, they charged to 54.5v, maintaining the volts and still drawing amps. Only 3 to 5 amps, but still, why can it not happen using utility?
Another interesting thing, last night I charged them using utility, but the stopped charging at 52v when they reached the bms stated capacity. Today using solar, they charged to 54.5v, maintaining the volts and still drawing amps. Only 3 to 5 amps, but still, why can it not happen using utility?
Trying to get to Naradas to re-calculate the capacity, I decided to run them empty. The Narada manual shows cut-off voltage is 42v. Unfortuanetly the lowest the inverter can go is 44v. Sooo, at 46.9v my batteries remaining capacity showed 0Ah. I pushed it down to 44v (running a bit higher load i wanted, but loadshedding was 1.5 hours away) the inverters switched over to utility! The Naradas capacity's changed. From 53Ah/56Ah to 74Ah/70Ah!! So it looks like i have to manually(put a dc load directly on batteries) drain the batteries to 42v so that I can have 100Ah capacity's Again!
DIYrich
Solar Wizard
Try charging to 54.5 hold there for a few hours to let the bms balance.
Raise voltage by 0.5v and repeat until you get to 57.0v.
The bms should reset sometime.
Raise voltage by 0.5v and repeat until you get to 57.0v.
The bms should reset sometime.
