Just picked up a battery extender for my SL by lbs didn’t give me the instructions and can’t find much info online. How much do you charge it for storage? I usually keep the bike at 20% guessing it would be similar for the extender?
The best storage voltage for lithium-ion batteries should be stored at whatever voltage is required to be at around 60-70% of its maximum charge voltage when not in use. This varies from cell type to cell type, but either way, the point is to avoid storing lithium-ion cells fully charged because the higher voltage range of a cell is where the chemistry inside is most reactive.
Don’t Store Batteries Too Drained, Either
Storing a battery at too low of a voltage won’t pose any danger or safety concerns, but it will hurt the batteries. If you begin a storage cycle with a voltage that is too low, then self-discharge could lower the voltage below 2.5V per cell, which irreversibly damages a lithium-ion battery.