1. Keep your lithium battery charged
Lit hiumabtteries are generally best kept fully charged, even after journeys of just a few miles. Completely discharging a lithium battery regularly will significantly reduce its ability to hold a charge, diminishing its capacity. If you do "flatten" your battery fully re-charge it as soon as possible.
2. Keep your electric bike battery clean and dry
There is little danger from a wet battery and ours are designed to cope with riding in the rain, though it is not advised. Contacts on the battery should be dried to avoid oxidation and corrosion which would weaken the ability of the battery to power the bike. Check the contacts every few months and clean if necessary. You could use emery cloth if there is any corrosion.
3. Keep your lithium batteries cool
A lithium battery is best stored in cold conditions where its internal resistance is greatest and will remain fully charged for longer. Camera batteries made of lithium are often recommended by manufacturers to be stored in the fridge to prolong their life. This isn't as easy with e-bike batteries! Store your e-bike battery in as cold a place as possible.