Dino's right, its not normally a fault in the back pack, in his case he's just full of static
,
I'm begining to wonder if they had a faulty batch?.
I do know that there is not a lot of room in the battery compartment, and when I first had mine I found myself forcing the battery cable into the space left, if you had the same problem, it could be you crushed the cables and caused a short circuit to cause this to happen, I'm not suggesting you did, just saying what could have happened?
Next time you put your battery into the backpack, gather the cable and plug to the side and you will find it all goes in neatly, and you should not have to force it in, if you find you can't turn the locking caps easily, then check your cable, as this is were the fault lies.
There are quite a few guy's on this forum, that use nothing but there backpacks for days in and days out, there a professional bit of kit, so they should be capable of working all day in my opinion.
P.S. Its a good idea to take your battery out completly to charge it.