It could be defective, or just elderly I guess. Some of those ego setups have been sitting around for a while, and that tends to degrade the battery.
Either way, I'd contact your vendor to do a warranty etc. I hope you have better luck with the next one.
One thing I never
buy on "clearance" is internal
batteries honestly. There is some older gear that's great, but the longer an internal battery sits on a shelf someplace, the higher the chance of the battery being degraded.
Anna