About three years ago, I built a small solar power system for my ambulance. I used it regularly over the past couple of years to run corded power tools and charge cordless tool batteries in a workshop. The other day, I noticed my tools beginning to run out of power, which was surprising because I had never discharged the pack to the point of failure before. When I opened up the battery bank, I found that one of the cells had ruptured, so I ordered one replacement 280AH LiFePo4 cell. After receiving the new cell I first top balanced the cells by connecting them in parallel and charging them to 3.5V using a variable power supply. I then reassembled the pack and reinstalled it in the ambulance. After using my tools for about a day. The cells had already gotten out of balance. The old cells all read in the 3.5-3.6 range, but the new cell stays around 3.35. Also, now the charge controller never switches to float mode. It just continuously charges the batteries. The battery light on the controller remains solid green, whereas before it always changed to flashing green after a days worth of charging.
I should add that the original cells were these VariCore batteries purchased from AliExpress, but I replaced the ruptured cell with an EVE cell purchased from Docan Power. When I first assembled the bank three years ago, I did not top balance them before assembly. I was a total novice and I did not know that was advised. Also, the batteries are in a pretty hot environment. In the summer it is usually well over 100°F in the back of the ambulance.
Here is a list of the main components I used to build this system:
What can I do to regain balance?
I should add that the original cells were these VariCore batteries purchased from AliExpress, but I replaced the ruptured cell with an EVE cell purchased from Docan Power. When I first assembled the bank three years ago, I did not top balance them before assembly. I was a total novice and I did not know that was advised. Also, the batteries are in a pretty hot environment. In the summer it is usually well over 100°F in the back of the ambulance.
Here is a list of the main components I used to build this system:
- 4 x 100W Grape Solar panels wired in parallel
- Renogy Wanderer Li 30A 12V PWM
- 4 x VariCore 3.2V 280AH LiFePO4 batteries
- Daly 4S 120A BMS
- Generic 2000W inverter
What can I do to regain balance?
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