Although Grumman Olson designed and built the Kurbwatt prior to building the Kubvan with a Volkswagen diesel engine which ultimately secured the contract for Grumman to build the LLV for the postal service and the success of the Kurbwatt, Grumman Olson was unable to attract a market due to changes in the energy crisis it is speculated. The history of Electric vehicles from that time is well documented and so no need to go into it here. The rugged light weight aluminum construction of the Grumman Olson truck body is the perfect design for an electric vehicle and a great starting point for an EV conversion.

Motor mount


I based this conversion on second generation electric vehicle design as all the parts were available on the used market at significant lower cost than building a current generation electric vehicle. That said see the EVII project page.

EV1 engine compartmnet arduino Battery Comnpartment Controller

I had major failure of the Curtis Controller for unknown reasons possibly running with very low batteries one day which may have caused excessive current load.

Curtis 1232 controller

The effects of a semiconductor failing while passing 20 + amps. What you see in the picture is the large Mosfets which have had the pin on the right side of the ring terminal vaporized and sprayed enough heat and molten material to melt away the tab of the adjacent smaller diode which outside of physical damage are still OK. This effect is repeated at each pair of Mosfet & Diode which make up a parallel circuit that passes some 500 amps to the traction motor. Pretty impressive! Would have made a cool video.

None the less searching for information on repairing the controller found this reverse engineered schematic of a Curtis 1221 controller which is very similar to my Curtis 1231. You can find this schematic here : Curtis 1221 schematic


Total investment for the conversion including used lead acid batteries was around $3000.00 cdn. in 2015.

More details to come :