EV Charging Plugs: Gateways to Power

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Underwriters Laboratories approves SAE J1772 charging plug: Virtually all of the automakers from the U.S., Japan and Europe are planning to use the standard plug on upcoming electric and plug-in hybrid vehicles, including in the Chevy Volt.

The charging plug is a critical gateway to success for electric vehicles, as was amply demonstrated during the 1990s.

Back then, GM promulgated the Hughes Electronics developed "Magnecharge" inductive charging system, touting the safety of its inductive design. However, a fire in the garge of an EV-1 leasee proved this was no guaruntee. Inductive charging relies on bringing two magnetic coils in very close proximity. Increased distance reduces efficiency and power transfer. If I recall correctly the fire was caused by a design flaw, where the Magnecharge 'paddle' would heat up if not inserted correctly, leaving the coils out of alignment. This was quickly resolved by GM and Hughes, but caused the EV community to collectively hold its breath, anticipating negative publicity which never came.

Meanwhile, Ford and Honda used the less glamorous "AVCON" conductive charging plug. The Avcon used a set of metal contacts, which were not activated until a 'circuit check' signal was received by the plug head. Only then, a circuit breaker would be magnetically closed to turn on the power.

The AVCON was an extremely simple design compared to Magnecharge. A small circuit board and a breaker was contained in a box about a foot square and a few inches deep. Magnecharge boxes were nearly one hundred pounds, had complete computer systems onboard that displayed vehicle charging status. It was nice, but was it really neccessary?

GM thought so, because they were using charging plugs to fight a bluRay/HD-DVD style format war. If they won, their competitors would need to retrofit all cars in the field. As it was, owners of charging locations needed to purchase at least one of each unit, creating the possibility that 'your' type of charging station might not be available in an 'EV charging' spot.

The J1772 standard is designed to resolve this before a format war breaks out. It supports two-way communication with the vehicle's onboard charging system, several charging power levels, and Vehicle to Grid -ready. Someday your EV may sell power back to the grid during periods of high demand.

While the article referenced above claims all is well, there is however an issue based on power differences in Europe and the US. In the US power is more commonly delivered at high amperage on two 'pins'. In Europe, at somewhat lower amperage on three 'pins'. Thus a different standard has been proposed by Daimler and RWE.

Who will win? With millions at stake it should be interesting to watch. But this time around it doesn't appear we'll have two standards in one country.