if I may step in.
I would suggest that what you do is start at the beginning, and make no assumptions.
To start in the beginning of this unit's troubleshooting procedures (the book says 'before any other troubleshooting') would be to start with the truck drive tires off the ground, a good and well charged battery, and battery disconnected, and to check each and every power (not the small control wires, but the heavy cables) cable on this truck, and to insure that none have less than 100k ohms resistance between any part of the cable and the frame of this truck (NO GROUNDS). Trace and isolate any place you have less than 100k ohms, this includes the power cables that run under the battery compartment. Replace any cables that are cracked or seem to have the insulation 'swollen' or soaked from contamination (either oil or battery acid).
Once you are positive NO power cable on this truck has less than 100K ohms resistance to frame with battery disconnected, remove the battery from the truck (do not set on forks) and try to see what happens when you try and drive. With the battery electrically isolated from the truck frame, if you still have the same symptom, then the rest of the suggestions are the next steps, but get it 'clean' first.
if it still is the same, the next steps will involve you giving us the voltage reading on the 2 strips of screwed in wires on the EV100 card (they are number l for left and r for right and then 1 to 9, and what we will want to know are the voltages (with respect to battery negative) all these, but the correct answer will change depending on what step you are in in the normal start-up sequences.