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8,155 Posts
I'll copy my post from the other thread.
I'm running bottom balanced without a BMS. My SE/CALB cells range in capacity from 110ah-114ah. Four months after my initial bottom balance I checked again and they were all within less than 0.08 volts of each other. I rebalanced again with a more accurate meter so they were all within 0.004 volts of each other and I'll check them again in December. I've pulled 5.5C from the cells occasionally and had one low discharge event to an average of 1.77 volts per cell yet they've remained well balanced at the bottom. I do undercharge the cells to be safe. The PFC voltage trim is a bit less accurate than I had hoped. If I need a full charge I'll flip the charger back on for another 15-30 minutes while I monitor closely, but not very often. I like the safety bottom balancing gives me while driving in the event of low SOC but as long as you stay away from the top and bottom I think you can get away with top, bottom, or middle balancing, without a BMS. I do have an adjustable charger, PFC-30, so I can change current draw and cutoff voltage as temperature changes the resistance of the cells. If I did not have an adjustable charger and wasn't using a BMS I'd probably top balance the pack. I'm using Dimitri's EV Display for amp hour counting which makes life easier being able to see how much charge goes into and out of the pack.
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I'm running bottom balanced without a BMS. My SE/CALB cells range in capacity from 110ah-114ah. Four months after my initial bottom balance I checked again and they were all within less than 0.08 volts of each other. I rebalanced again with a more accurate meter so they were all within 0.004 volts of each other and I'll check them again in December. I've pulled 5.5C from the cells occasionally and had one low discharge event to an average of 1.77 volts per cell yet they've remained well balanced at the bottom. I do undercharge the cells to be safe. The PFC voltage trim is a bit less accurate than I had hoped. If I need a full charge I'll flip the charger back on for another 15-30 minutes while I monitor closely, but not very often. I like the safety bottom balancing gives me while driving in the event of low SOC but as long as you stay away from the top and bottom I think you can get away with top, bottom, or middle balancing, without a BMS. I do have an adjustable charger, PFC-30, so I can change current draw and cutoff voltage as temperature changes the resistance of the cells. If I did not have an adjustable charger and wasn't using a BMS I'd probably top balance the pack. I'm using Dimitri's EV Display for amp hour counting which makes life easier being able to see how much charge goes into and out of the pack.
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