I know no one wants to hear "spend more money", but I found this little item to be very handy in checking LiPo battery capacities and voltage on the fly:
http://www.amainhobbies.com/product_...attery-Checker

It's $32, and well worth it to me.

Eventually, getting a charger with the storage feature should probably be on your radar (for long spans w/out running - months, and such). But the $32 item above at least is something to get by with in the meantime, even when you just run your RCs a bit to get the battery down enough for storage.