New owner - Charging question

[TonyWilliams]

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Thankfully, I have a modified 2013 Nissan LEAF / Panasonic that I could dial down to 8 amps and it worked.
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NOTE: Tesla charger will pull maximum 20 amps on 100- 120 volts, and of course, 40 amps on 200-277 volts.

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If the Tesla charger pulls 20 amps how does the "dialed down" Panasonic EVSE tell the charger to pull less amps. Is this done with the J1772 signal or changed resister value?

The J1772 EVSE generates a one kHz square wave, which pulse modulates the amperage.

http://code.google.com/p/open-evse/wiki/J1772Basics