eprosenx
Active Member
I don't think it's a software issue. How long did you leave them each pulling 20A? The battery heater can pull around 6kw; at those temps I've plugged a cold-soaked car into a 30A circuit, pulled 24A for a while (at least an hour or 2) without any increase in charge level. Once the battery warms it should start to charge slowly. As it continues to warm, the charge speed will improve.
The trick is to plug in and start charging as soon as you get home while the battery is still warm, or just be patient.
I wonder if that explains the issue. If the battery heater is a 6kw resistive element then it would need 25 amps just to operate. So if the HPWC only gives each car access to 20 amps, neither can get enough to fire up the heater to heat the battery pack to the point it is safe to charge it.
So if the HPWC was smart enough, it could recognize this situation and allocate all the power to one car for a while and then later to the other car and achieve charge on both. But that would require a LOT of logic and two way communication for the HPWC and I just don't know that complicating that protocol makes much sense.
Sounds like the Telsa needs better alerting to the driver/owner of what is going on (i.e. insufficient charge current available to run battery heater).
Maybe @Duckjybe could find a way to up the power on his HPWC's to a 60a breaker (or higher) which might give him the margin necessary for both cars to simultaneously warm their batteries. If he was lucky he would already have the wire of the necessary ampacity and sufficient capacity on his main service feed. Like if it was #6 AWG and run in conduit (not NM romex cable) then he could just swap the breaker to 60a and change the HPWC settings up a notch and be golden.