I get the question on how to store lithium batteries when not using them for a while.
As this popped up again today, I thought I would very quickly post my thoughts on this topic as well.
Here’s what I tell customers: if you really abuse the batteries (within reason), you might “only” get 2000 cycles out of them, instead of the 4000+ cycles they might get if they are a bit more careful.
However, given that our average customer does less than one cycle per week, 2000 cycles is around 40 years!
Obviously, that’s not factoring in time-based degradation, but it makes the point that there’s usually no need to try and get every last possible cycle out of the batteries.
On the flip side, however, you definitely should not store your batteries when they’re flat (or close to flat)! The main reason for this is that while LiFePO4 batteries have a much lower self-discharge rate than lead acid, they can still be around the 3% per month mark. This means that if you store a battery that has 10% of charge left for 4 months, you might drop below the minimum recommended cell voltage of 2.5V, which can damage cells and reduce their capacity, especially when recharging with high currents.
Also as with seemingly anything on the planet, they should ideally be stored in a cool dry environment but again, as long as you don’t store them at temperatures above 40°C, it won’t really matter too much.
As for myself, I store customer batteries at 40-50% but happily keep my own at 100%.