IF the battery is fully discharged this could easily be the reason your charger is tripping out - short n sweet it is OVERLOADED by totally dead battery.
SOLUTION put a pretty good battery across charger and charge for 30 minute. Turn off and parallel bad battery onto the good one.
Expect some arc n spark - let sit for 10 minute. Turn charger on. The reason this works is the good battery is sharing the load thus unloading (partially) the charger.

Now to find your ground ie short or really a partial short.
1. Disconnect one side or other of battery preferably the non grounded side.
2. Pull all fuses check for current. IF gone reinstall one fuse at a time and check for current.
3. Break apart the starter solenoid connections and reconnect one - checing for current each time.
4. It should show up on one of the wires. 5. Start hand over hand tracing.

Dan Bentler