July 5, 20232 yr You should run it at absorb for a few days. If you have solar then disconnect the solar and run from grid for a few days to give the batteries a fighting chance to get balanced. While you are cycling the balancing will take ages due to the low balance current most builtin bmses use.
July 7, 20232 yr On 2023/07/05 at 2:59 PM, Oros said: Hi, Without stripping my battery, how can I top balans my batteries. I notice your "Min Cell Voltage" doesn't display the actual lowest cell voltage. Could it be that the BMS doesn't think balancing is necessary? What BMS is this?
July 7, 20232 yr Author 31 minutes ago, jumper said: I notice your "Min Cell Voltage" doesn't display the actual lowest cell voltage. Could it be that the BMS doesn't think balancing is necessary? What BMS is this? It is Narada 48NPFC100.
July 7, 20232 yr 28 minutes ago, Oros said: It is Narada 48NPFC100. A quick look online suggests a charge voltage of 54V for this battery, but you are sitting at 51V currently. I think you need to increase your bulk voltage to something like 52.5V and see if that helps. My battery would sometimes sit for ages and the passive balanceer would just charge and burn off the higher cells and never really charge the lower cells until I pushed the voltage up a bit. If you have comms between the battery and inverter then it 'should' be setting the correct voltage for you though. Got the battery info here: https://www.fullcirclesolar.co.za/wp-content/uploads/2021/09/FCS-48NPFC100_-5U-_Side_Handles.pdf
July 30, 20232 yr Author What confuses me about these batteries is that they are both 100Ah, but their capacities show 56.3 Ah and 53.3 Ah. The SOH on both is 100%. Where did I loose the capacities of the batteries. If some cells is damaged, should the SOH not decrease?? I read that the SOH is calculated by looking at the internal resistance of the cells. As cells age, the internal resistance will change. So why is mine still showing 100%. Could it be from the imbalance of cells? Is that why the capacity is showing lower values? The 0% SOC of these batteries is 44V. At 46 V they are flat or empty, and switch off. I'm at the stage that I want to strip the batteries, top balance the cells and then see what the BMS shows regarding the capacity. It's going to take time as high amp adjustable chargers is not availible in SA. So I'm going to use 2 X 10 amp and connect them in parallel, and charge 3 cells at a time. Also thinking of replacing the BMS with a JK active balancing BMS.
July 30, 20232 yr Are you currently running in Li BMS mode with comms? Try voltage control mode without comms for a day or two. Set all your voltages and charge rate manually on the Inverter and let the BMS manage the charge, that is if you haven't tried it yet
August 24, 20232 yr Author On 2023/07/30 at 9:41 PM, zsde said: Are you currently running in Li BMS mode with comms? Try voltage control mode without comms for a day or two. Set all your voltages and charge rate manually on the Inverter and let the BMS manage the charge, that is if you haven't tried it yet I have axpert inverters, they do not have comms with narada batteries. So I monitor the batteries via icm. At this stage I can not charge the batteries higher than 52.2v. If i go higher, then some cells go as high as 3.7v. So, 52.2v= to +- 3.48v per cell. But my batterys is so unbalanced, that when some cells is at 3.65v, a few is only at 3.33v. I'VE tried charging with lower amps, higher amps, manually drained some cells to see if it will lift total voltage, nothing works. I am thinking of replacing the bms, or adding a 5a cell balancer.
August 24, 20232 yr 3 hours ago, Oros said: I have axpert inverters, they do not have comms with narada batteries. So I monitor the batteries via icm. At this stage I can not charge the batteries higher than 52.2v. If i go higher, then some cells go as high as 3.7v. So, 52.2v= to +- 3.48v per cell. But my batterys is so unbalanced, that when some cells is at 3.65v, a few is only at 3.33v. I'VE tried charging with lower amps, higher amps, manually drained some cells to see if it will lift total voltage, nothing works. I am thinking of replacing the bms, or adding a 5a cell balancer. At these levels you will have to do manual balancing say 4 at a time on a 12V PSU. Once 12 have been done the last 3 can be done on an adjustable PSU. If no adjustable PSU connect the last 3 in parallel 1 to the highest of the other 12 already done. Then the 2nd one to the 2nd highest and also the last one to the 3rd highest. Leave connected for quite some time. Then lastly Al 15 in parallel and then you will need an adjustable PSU for the final step adjusted to about 3.6V This what I think you can do.
September 1, 2025Sep 1 The cells going above 3.7V have higher internal resistance. No matter how many times you balance them they will eventually fail. I had the same problem with Narada 48npfc100 15 cells battery. Those cells had ir value of 0.68 to 0.82 milliohms. They were bit swollen as well. Replaced those 4 or 5 cells and battery was performing okish
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