Portable DVD not working when battery connected

[Cranerman]

I'm trying to find out if anyone has seen this before:

I have a Polaroid PVD-0700 which does not turn on when the battery is connected.
The AC adapter is plugged into the device so it is receiving power.
When I disconnect the battery and run it off the AC adapter, it works fine.
On the AC adapter, there is a red LED which indicates the transformer is powered.
When I connect the power plug with the battery inserted, the light goes out and the device does not work. When I connect the power plug with no battery, the red LED is lit and everything works fine.

My guess is the battery is dead, any suggestions?

[Krispy Kritter]

The battery is the most likely culprit and there usually isn't anything that can be done to repair them, they just wear out. It could also be a faulty power connector or part of the power circuitry has failed. Either way, you won't know for sure without testing another battery.

[SLK001]

The battery probably has a shorted cell. It is drawing more current than the AC adapter can supply.

Simple fix - replace the battery.