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Old 04-11-2017, 12:31 AM   #3103 (permalink)
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Originally Posted by MPaulHolmes View Post
I just bought the chademo protocol ($145) earlier today. Well, I'm pretty sure that's what it is. It was from Japan. They seem to say that the car commands the current, which would flush my MPPT charging idea down the toilet, as I can't send 100amp at 400v into the battery pack from my panels just because the car gets it in it's head that that is what it wants. If that's really how it works, I couldn't begin to guess why they would design it that way.
My understanding is that the car commands the current and generally does the charge control. So it asks for as much current as it can take - for fast charge and the like.

The Chademo, or the J1772, sends in a message how much current and at what voltage the current is supplied. I think this is several times per second. As the battery is charged, the Coulomb count rises, etc the car determines that it should be switched into constant voltage mode. It asks for less current until the voltage drops to setpoint for constant voltage, until the current drops under a threshold, or a timer expires, or some other criteria for 'battery full - stop now'. I think the procedure was originally a method to allow for the same request by the car from any charger.

EVTV posts that Tesla performs a 'reset' .. I think .. every minute or two to allow the charger to send a message with how many amps are available for charging ... or something like that. I can't locate the post just now ..

As for MPPT, I think it makes sense to implement and send the car the status message with output volts and amps ... see if it is OK with that. Damien Maguire has some (maybe a lot?) of logs of charging his land yacht at various charge stations. I think EVTV have code posted for both sides of the conversation. I'll have to look!
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freebeard (04-11-2017), HaroldinCR (04-11-2017), MPaulHolmes (04-27-2017)