need battery help....

[helirook]

i have posted this already in the blade cp/cx section, then realized it should go here.... sorry....

so i haven't run into any trouble w/ my trex yet.... but w/ my blade cx, the battery does not seem to be charging up, it only flies for about 60 sec. i put it back on the charger (the one it came w/) and wait till it says it's good, i check w/ a DVM, says 8.4v..... must be good.... nope, same thing. the battery was workin' fine till i let it sit for a week. i didn't think these needed daily cycling.... what am i missing here. even after i try to fly it for about 60 sec., realize that it has no juice, measure again, it still says 8.4v..... someone drop me some clues. i am new to elec. and battery stuff..... and at this time i haven't picked up a triton or anything fancy.... still using the cheap chargers....