I have a Tandy 1100FD with a bad gel battery (6v, 4.8AH)

It runs fine from wall adapter, but reboots constantly when supplying 6v through the battery jack.

It runs through self-test fine, but immediately restarts on first floppy seek. I've upped the voltage as high as 7v with no change.

Any suggestions as to what to look for? Is my power supply not providing sufficient amperage, maybe? 2.5amp should be sufficient as far as my math says.

I've verified which connectors are providing positive/negative.