If you have a pack that is more than 1P (like 14S2P, 13S6P, 20S8P, etc) then the Ah is calculated by multiplying the P number by the individual cell Ah. 14S2P made of 20Ah cells is 2P x 20Ah = 40Ah.Can someone explain how the battery Ah is calculated. I see cells that claim to be 25Ah but my whole pack was supposedly 45Ah and it has 20 cells.
If the pack is only 1P, then the pack Ah is the cell Ah. 14S1P made of 20Ah cells is 1P x 20Ah = 20Ah.
If you don't know the P number and/or don't know the individual cell Ah, you can't calculate the Ah.
In that event, you can first fully charge the pack, then install a common RC Wattmeter, Cycle Analyst, etc., between the battery and the controller, then go ride until the pack is empty and shuts off, and note down the Ah (and Wh) readings the meter gives.
Note that most common wattmeters do not store the data so if it actually powers off it loses all the info, unless you follow the directions for it to install a tiny separate backup battery or aux battery that just powers the meter (and not your system). The Cycle Analyst remembers the data when powered off so it doesn't need this.
If you can't use a meter that stores the data and can't separately power it, then you will need to do the opposite test---ride around and discharge the battery till it shuts off, then install the wattmeter between the charger and the battery, and fully charge it. The Ah / Wh readings you get this way will be higher than the actual battery capacity because charging isn't 100% efficient, *and* because the system may take time to balance the battery, which uses extra power in the process, that will be counted in the Ah / Wh reading but isn't actually part of the available pack capacity. (this is why I recommend doing the first test instead).
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