City Car Kyle was helping a friend who had somehow managed to chop the cord and plug off his only 110 volt EVSE for his Nissan Leaf. This left him with no way to charge his only car. Kyle gave him a EVSE in trade with the home of converting it from a 110 volt to a 110 or 220 volt EVSE charge plug. Kyle had nothing to lose; letting out a little magic smoke wouldn’t make it any more broken (as long as it wasn’t let out with Kyle in circuit).
After doing some research and examining the innards of the EVSE, it looks like three wires go into it, two of which are switched and monitored (the neutral and line); the ground is simply grounded. Rewiring it with a NEMA 13/50 three wire 220V plug should be possible by simply using the neutral as the second 110V line in.
It worked. Now Kyle has a portable 220V EVSE capable of 12 amps at 220 volts, or twice the charge rate of the original charge cord. There was one additional difficulty to overcome: the 110 three prong plug end had been cut in half. Within the plug end was some type of resistor. We think its a thermistor that is wired into the charger’s control board. The control board needs to ‘see’ a specific resistance, + or – some unknown amount, in order to continue charging. This is so that when it gets warm, or in this case too warm, the resistance in the thermistor changes and once it’s outside of the acceptable operating range the EVSE shuts off. It’s a simple but effective way to prevent the plug from overheating and burning the house down while charging.
We had to measure this resistance and add a resistor to the control board in the EVSE, which is not as effective to prevent overheating but is very effective in making the EVSE capable of charging at 220 volts.
According to a short update I received from Kyle, the 220 charger only works for a short period then shuts down. Although it worked fine on the Smart Electric Drive and IMW Seven, on a vehicle that can’t use a ‘cheater’ cord – a non-EVSE compliant charge cord that’s missing the proximity and/or pilot signals– the 220 cord only works for a few tens of seconds and then his vehicle stops charging. The Smart seems to need only the proximity not the pilot. and Seven doesn’t need either, so a ‘cheater’ cord works fine for them.
Our guesses? We think that it’s something to do with the pilot signal, other than that we haven’t confirmed anything yet. It’s a work in progress.