I have marked ( numbered ) my batteries as i have 7 , if you are not keeping a flight log , you need to do so to insure you keep a history of all things H . I also log my battery time / use/ storage / after every flight , even if a battery does not get used in flight , it gets discharged to storage level. Stickers are greatd , but if you fly commerical , the FAA may at some time , want to see your log/s ...