ROBOTIS MINI should be used with two LB-040 batteries.
This is because recommended input voltage for XL-320 is 7.4 V.
It seems like you are using too high input voltage for the robot which can damage the electronic components including XL-320.
Please use recommended power source for ROBOTIS products.
I guess its pointing to the wall supply as the culprit or the battery itself. I suppose its more likely i damaged the battery, but if so, why does the charger fault even with no battery connected? Maybe i damaged the wall supply? I should probably go and try to charge the battery with the car battery and see how far it gets along.