Exact same for me, I had one I picked up at Wal-Mart years ago after a similar experience but lost the charger during a move. I just tossed it anyway, it took FOREVER to charge and lost the charge ridiculously fast when you used it for anything, including charging phones. Looking for something more high quality and durable this time around.
circ - Good point on the trickle charger. I've seen them sold separately, but it looks like some boosters come with an "intelligent charger" included that automatically switches between active charging and trickling depending upon battery level.