Lithium batteries must never drain below a certain voltage so are never normally flat. There should be control/protection circuits in EGO's to ensure this so despite having energy the batteries shuts down to protect themselves. So they always have say a 20% charge. Normally they are stored at 40% charge and don't drop much. So all these 40% batteries are causing this postal issue.

We should also store at around 40 to 50% charge if it's for a long time.

Make sure you use the USB charger and/or Wall adapter that was supplied.

Ego's are all protected however there are unprotected and protected batteries available for MODs.