Thu 27 Nov 2008
Yesterday the truck failed an important test. It rained and it cause a ground fault. Even with all new seals on the lid and gasketed washers, it still ground faulted. So I got into the pack and checked for ground faults with the volt meter. The ground fault was floating around as it had on me earlier this year. So I tried the meter in low current mode set to milliamps. It showed the same location for a ground fault. Removing the cells showed some KOH streaking. Cleaning it up did not change where the ground fault was shown to be. So I went to the new process that I had figured out last Feb. I removed a cell interconnect at the lowest voltage reading relative to ground. I kept pulling one copper bar at a time until the voltage suddenly shot up. It ended up showing me that the ground fault was in the rear drivers corner of the pack. Removing the 8 cells in that area showed that there was water between the corner of the cell and the wall of the battery box. So I cleaned off the walls and cells with diluted vinegar and reassembled the pack. That took care of that ground fault!! This time I moved the mylar insulator into the corner to help isolate that corner cell from the box if it gets wet again. There is another smaller ground fault on the passenger side of the pack. I just vacuumed in that area and called it good for now.
The rear edge seal was a different material since I had run out. So I tore it off and installed the correct material. Since the two ground faults I found were right under that seal, this could help.
Also I adjusted the ground fault setting in the software to give it more tolerance since having 252 nicads or 504 terminals is almost 5 times the terminals that a regular lead acid pack would have. Between that and having flooded nicads, the pack is more prone to having ground faults. So I will see during the next rain how it all functions.
Leave a Reply
You must be logged in to post a comment.