I guess anybody buying Lifepo4 batteries from the wildly popular but perhaps not always completely trustworthy Ali[a-z]* is bothered by the fact that you need to test your batteries within a certain amount of time (14 days is standard) if you want to claim any kind of protection. Let's for a moment just assume that there IS protection.
Of course, a battery that does not charge of has obvious external damage is easy to spot. I am more worried about batteries that are sold as capacity X but actually are of capacity Y where X is (much) larger than Y, and also about large variations in capacity of the cells I plan to use.
Since I am planning to buy 32 cells of 200...280Ah, it would be quite time consuming to charge all cells individually, then discharge them to determine their capacity.
I have charging capacity for 8S cells at 200A (adjustable down) and a microcontroller system to measure all 8 cell voltages individually while charging with microvolt accuracy.
I was wondering if it might then be possible to determine the capacity by charging and discharging ONE cell, then charging it once again to the same voltage/SoC as the other cells (assuming these voltages are all the same) and then putting a 0.5C charge on 8 oif them in series. After a possibly short while, the cells with lower capacity should show higher voltages. My question is if anybody tried this approach already to test battery capacity, and if there might actually already be a mapping of delta-V to delta-Capacity out there... Ok last question is a very long shot ;-)
Of course, a battery that does not charge of has obvious external damage is easy to spot. I am more worried about batteries that are sold as capacity X but actually are of capacity Y where X is (much) larger than Y, and also about large variations in capacity of the cells I plan to use.
Since I am planning to buy 32 cells of 200...280Ah, it would be quite time consuming to charge all cells individually, then discharge them to determine their capacity.
I have charging capacity for 8S cells at 200A (adjustable down) and a microcontroller system to measure all 8 cell voltages individually while charging with microvolt accuracy.
I was wondering if it might then be possible to determine the capacity by charging and discharging ONE cell, then charging it once again to the same voltage/SoC as the other cells (assuming these voltages are all the same) and then putting a 0.5C charge on 8 oif them in series. After a possibly short while, the cells with lower capacity should show higher voltages. My question is if anybody tried this approach already to test battery capacity, and if there might actually already be a mapping of delta-V to delta-Capacity out there... Ok last question is a very long shot ;-)
