Telemachus
10 W
I inherited some hover board battery packs, so I decided to mess with them a little bit in preparation for building some larger batteries.
The first thing I noticed is that the overall voltage of the battery was only 24V (should be 36). I took it apart, and found that 2 parallel sets were drained all the way to zero.
*** First Question: Should a BMS allow you to detect a voltage on a battery when some of the cells are all the way depleted? Isn't it supposed to cut power off?
I created a 6S1P battery using the remaining good Samsung 18650-22P cells. I then attached the BMS that came with the battery back, but I only attached the B- Lead and the first 6 charging leads. I thought I would have to bridge the other 4 wires, but the voltage was registering at 22V so I just went with it.
I wrapped the battery up, and carefully watched it while it charged up to 25.2 Volts with a 6S charger.
After full charge, I checked the voltage of each cell. Most were around 4.15 volts, but there was one at 4.3 and one at 4.22.
I figured I'd see if the BMS would do its job, and bring these down, so I let it sit overnight.
This morning, all of the cells had dropped about 0.01-0.02, but the 4.3 was still at 4.29.
*** Second Question: How quickly should it be able to drop the cells to an appropriate 4.2 volts?
The first thing I noticed is that the overall voltage of the battery was only 24V (should be 36). I took it apart, and found that 2 parallel sets were drained all the way to zero.
*** First Question: Should a BMS allow you to detect a voltage on a battery when some of the cells are all the way depleted? Isn't it supposed to cut power off?
I created a 6S1P battery using the remaining good Samsung 18650-22P cells. I then attached the BMS that came with the battery back, but I only attached the B- Lead and the first 6 charging leads. I thought I would have to bridge the other 4 wires, but the voltage was registering at 22V so I just went with it.
I wrapped the battery up, and carefully watched it while it charged up to 25.2 Volts with a 6S charger.
After full charge, I checked the voltage of each cell. Most were around 4.15 volts, but there was one at 4.3 and one at 4.22.
I figured I'd see if the BMS would do its job, and bring these down, so I let it sit overnight.
This morning, all of the cells had dropped about 0.01-0.02, but the 4.3 was still at 4.29.
*** Second Question: How quickly should it be able to drop the cells to an appropriate 4.2 volts?