On a personal note my had an issue yesterday. My Lead Acid batteries were 75% charged when I parked it one month ago. After driving at full speed for 5 minutes it would only let me go at 10 km/h. If I tried to go faster the controller would disengage. I think it has something to do with the poor discharge rate of my Lead Acid batteries.
If you have any questions that you will want to be answered in this series it will be a good idea to post them here so I can incorporate the answer to them in the series.