OK if you have to struggle even with the lack that smartphone batteries last only as long as the working day is long (and even if you're lucky) then this SAMSUNG Reserve a abolutes must. Small, compact and fast charged with the original phone charger. And the battery can be left in charge of this case also, although even an additional box is beige Pact. just awesome! At least until the day when smartphone battery last longer and hold than one working day. (As I said - if you're lucky)