Hi Chris,
Ideally, an unused battery should be recharged every 6-8 weeks when not in use to ensure the cells remain as balanced as possible, and also to ensure that cell voltages don't fall too low due to natural self discharge of the cells combined with the parasitic current drain of the battery's
BMS.
Hopefully the battery will not self-discharge too quickly, but it might be better to charge it fully overnight
(or at least 8 hours) to ensure the individual cells are well balanced before leaving it to stand for 6 months in a cool and dry location.
Make sure it is turned off and unplugged from both the bike and the charger while it is being stored, and when you return, give it a nice long charge again to allow all the cells to become equally balanced before using it.
If you were to leave it in a partially discharged condition, the weakest cell
(which would already be at a lower voltage than the rest) would become overdischarged much sooner.
keeping a battery fully charged on a continual basis may not be recommended as it can reduce the lifespan of the battery, but as your battery has to stand for 6 months without any top up charging, I think a full and well balanced charge prior to being left uncharged for 6 months would be more beneficial to the overall health of the battery and should ensure the best chance of survival.
I think the minimal reduction in its lifespan would be infinitely better than dead cells and an unusable battery.
Alan
