Problems

I worked from 1989 to 1993 in a project developing an Electric Van. It was based on the Japanese Subaru minivan chassis and used lead-acid batteries with a series wound DC motor with MOSFET controller connected to the original clutch and 5-speed gearbox. Top speed about 70 km/h but in city traffic it was perfect. The Curtis PMC controller is similar to the model used in the Elcat minivan, a 1209-6402, which was a very quiet and efficient unit. The characteristics of the series wound DC motor made it accelerate well with lower speeds. The biggest problem was the batteries. There were 12 batteries (12 volt) in total. They were connected six in series and another six in series in parallel to produce 72 V operating voltage. The problem was that when the batteries were used for awhile some batteries were not fully charged due to the minor differences in the batteries' properties and this created imbalance in the battery pack. And because the total performance is defined by the weakest link the range per charge dropped dramatically. I guess in general building an electric drivetrain is easy and cheap when the top speed is low. There are a lot of electric forklift trucks with suitable components.

Offered by Olli.

I think our most efficient batteries configuration would be made up of a series of rebuildable single cells. I have found some very large single cell Nicad (not rebuildable though). Haven't seen any large single cell lead-acid. Finding rebuild-ability is even tougher. The industry is into disposability. With battery packs made of single cells one can swap out a single cell if it gets weak or dies.

Offered by Mike.