EZ Flash isnt rumbling

i just recently got an EZ flash 3 in 1. i downloaded some software for it and used it for a couple of days and it worked fine. but now it doesnt rumble anymore games that its supposed to rumble on. instead what it does now is make a really soft rumble on all settings.does anybody have any idea what this could be? i dont think its the software cos the ram expansion settings and the gba roms work fine...therefore im guessing its the internal battery for the rumble pack...anybody got any ideas. i bought this off some guy on ebay.im using an nds lite with an r4 card 1 gig kingston with 1.16 firmware. for the ez flash im using gba exploader v0.57

It's probably run out of the rumble battery yeah.