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Power Failure and difference between HPWC and UMC

Power Failure and difference between HPWC and UMC

If you turn the power to the UMC ( portable EVSE) off and then on, the car will start to charge again. If you do the same thing with the wall charger, the car will not restart charging until you have unplugged the car and plugged back in. Why the difference?

If you go away on holidays, leaving the car plugged into the wall charger and there is a short power outage ( storm damage etc) then charging will not resume. If you are plugged into the UMC, then charging will resume after the power failure. It will make a big difference when you get home!

The reason I am interested is actually a bit different. I have a solar charging facility for the car. There is nothing available on the market for a solar inverter to communicate with the wall charger or the car. I control the charging by switching the power to the UMC off and on using a standard signal from the solar inverter based on the state of charge of the solar battery. Simple stuff, but it won't work on a wall charger. Why not?

Why can't we get a car charger to communicate with a standard solar BMS (battery management system) and control the car charging?

SO | February 11, 2019

I have a HPWC with my Tesla MS plugged in. There are times when I shut the power off to the HPWC. I then turn it back on a bit later. (This last time was because the power was flickering due to ice storm power restoration. Other times are during severe lightning.)

The car charged normally that night without me doing anything to it.

rxlawdude | February 11, 2019

@SO, but was the car actually charging when you cut the power? I think that's the use case OP is talking about.

TeslaTap.com | February 11, 2019

Or it may be time of day charging. If you have it set to midnight start charging and it is interrupted after midnight, I don't think it restarts until the next night. Can't say I've tried it though.

SO | February 11, 2019

@rx - my car was not charging at the time I turned off the power.

I left it off overnight and the App stayed there was a problem charging.

The next day, I turned on the power to the charger. That night it was scheduled to charge, and it charged.

I do agree with TT that if scheduled, it probably will not restart until next scheduled charge time.

milesbb | February 13, 2019

@witjweri
I think the solution to charge control through HPWC is in using the load share input connection. I suspect you will be able to control charge current over a wide range by impressing a small DC current/voltage at the load share connection on the HPWC. Of course the control range needs to be hacked by someone willing to do a number of tests to determine HPWC response to applied input.

rxlawdude | February 13, 2019

@SO, pardon me for my denseness, but "not charging at the time [you] turned off the power" but stating that after turning the power on, it charged as scheduled.
Between turning the power off and back on (and later scheduled charging starting), did you keep the charge cable connected?