Li batteries at 48vdc
After much deliberation and questions, I'll likely be purchasing the 48v Lithium battery pack instead of 4-12v. I liked the idea of 12v batteries for weight and ease of handling, but the possible cel...
Forum Discussion
You need at least 4 prismatic cells in series to make the 12v groups, then you need 4 of those in series to make the 48v. In the minimal configuration that would be would be 4s(1p4s). Or for 8 cells per 12v group it would be 4s(2p4s) and so on.
In this configuration you have 2 layers of series connections and thus more likelihood of imbalance cropping up because series groups cannot be balanced in LiFePO4 cells. You have to apply 1/4 the voltage to each cell to balance.
This is not an issue for lead acid batteries because you can just overcharge the cells to equalize (balance) them which will damage LiFePO4 cells.
However, you can also connect them as 1p16s or 2p16s.....etc etc which is only one layer of series connections.....least likely to get out of balance.
Another way to look at it is that series (s) is bad, parallel (p) is ok and if we multiply the configuration out:
4s(1p4s) = 16*(p)*(s^2) and 1p16s = 16*(p)*(s)
4s(2p4s) = 32*(p)*(s^2) and 2p16s = 32*(p)*(s)
if s is bad, s^2 (s squared) is much worse.
In this configuration you have 2 layers of series connections and thus more likelihood of imbalance cropping up because series groups cannot be balanced in LiFePO4 cells. You have to apply 1/4 the voltage to each cell to balance.
This is not an issue for lead acid batteries because you can just overcharge the cells to equalize (balance) them which will damage LiFePO4 cells.
However, you can also connect them as 1p16s or 2p16s.....etc etc which is only one layer of series connections.....least likely to get out of balance.
Another way to look at it is that series (s) is bad, parallel (p) is ok and if we multiply the configuration out:
4s(1p4s) = 16*(p)*(s^2) and 1p16s = 16*(p)*(s)
4s(2p4s) = 32*(p)*(s^2) and 2p16s = 32*(p)*(s)
if s is bad, s^2 (s squared) is much worse.
