I have caterpillar E6000 electric forklift, the battery is fully charged, turning the key off and on ,the bars on the battery level will drop, some times all the way down to 3 bars then dead, turn the switch off and on again and it might go back up might not, plug the battery into another forklift and its completely charged, but the forklift will quit moving when the dash says it's dead, even though the battery is charged. Any help appreciated.