HPWC shared circuit potential issue

[PhaseWhite]

I have 2 HPWC connected to the same off peak meter 60AMP circuit and they are mostly doing what I expect however when I have both plugged in but only one car charging I was expecting to be able to get the full 12KW of power on that one charger but what I am seeing is just having both chargers plugged in results in only getting 6KW regardless of if both are charging or only one is charging. This is kind of annoying because if I want a faster charge I have to go outside to the garage and unplug one.

Is this normal or is something perhaps screwed up? Notably my Model 3 has the firmware version with winter optimizations that no longer locks the charge port until charging is initiated.

 

[Tam]

...unplug one...

I don't know about your exact numbers above but I expect what sharing means.

In general, on one 100A circuit, the maximum a HPWC can deliver is 80A. When you use 2 of them at the same time, the maximum each can is 40A each.

There is absolutely nothing wrong with disconnecting one in order to get the maximum rate.

 

[Cirrus MS100D]

I think was OP is alluding to, and what I thought would happen (we don’t have a second Tesla... yet...) is that it would automatically balance the rate between the cars by “knowing” how much juice each needed.

Model S in bay 1, Model 3 in bay 2

Model S is at 70% and charging to 80%, getting full 12kW or whatever.

Model 3 rolls in at 20% and charging to 80%

Model S now drops to half (or less) and Model 3 gets half (or more)

After S is “finished,” then 3 should get full 12kW because S is done.

OP is saying this *isnt* happening unless the second car is unplugged and this doesn’t seem right.

 

[Rocky_H]

I think was OP is alluding to, and what I thought would happen (we don’t have a second Tesla... yet...) is that it would automatically balance the rate between the cars by “knowing” how much juice each needed.

That was the original announced functionality when these new wall connectors were first being introduced. And when they first came out, I read threads here on this forum of people testing and confirming it would do exactly that--dynamically allocate the amps between the two cars and give more amps to the car with a lower state of charge.
At some time later--I don't know when exactly--Tesla pushed an update somehow, so that it is an absolutely brain-dead split of the amps: 1/2 for two connectors, 1/3 for three, etc. It's certainly not the most effective usage of the circuit, but I suppose there was some problem Tesla found out about with the current shifting and Tesla decided to eliminate that functionality.

 

[brkaus]

It sounds messed up. My reading of the HPWC control thread is that something like 4-5a is reserved for a plugged in but not charging car.

Otherwise 50/50.

Or 100/0 if one unplugged.

Edit to add: I’ve been considering a second HPWC. If it’s strictly 50/50 I won’t bother.

 

[Blup85]

Maybe someone didn't set the "slave/Master setting correct for your HPWC?
per the manual, the master HPWC is set for the maximum current for that circuit (in your case, 48 amps which should read "9" on the dial). All other slave HPWC should be set to "F"

 

[brkaus]

It sounds like it is set because full current is supplied to a car if only one car is plugged in.

 

[csanders90D]

I just installed 2 HPWCs on a 60A circuit last month. To test that the installation was right, I plugged in both cars and started them charging. Each car correctly pulled 24A (half of the 48A continuous that the circuit can handle). Then I clicked "Stop Charging" on one car but left it plugged in and the other car ramped up to 48A.

So, I'm seeing the correct load sharing behavior. This is with S and X as the two cars, maybe a 3 does something differently.

 

[animorph]

I have an X and a 3 with two HPWC's sharing a 100A circuit. I set the switches myself, 100A breaker for one and "F" for the other. I use scheduled charging, one starts at 9PM the other at 11:30 PM. Looking at TeslaFi it looks like the earlier charging X mostly gets 40A. It should charge at 72A if the 3 isn't charging. (It does, just checked). It has charged at 72A at least once (maybe the 3 wasn't connected?). The 3 has been charging at 48A. I don't see it limiting to 40A. So not straight 40A/40A, but not maxing out for the X either.

 

[eprosenx]

I have an X and a 3 with two HPWC's sharing a 100A circuit. I set the switches myself, 100A breaker for one and "F" for the other. I use scheduled charging, one starts at 9PM the other at 11:30 PM. Looking at TeslaFi it looks like the earlier charging X mostly gets 40A. It should charge at 72A if the 3 isn't charging. (It does, just checked). It has charged at 72A at least once (maybe the 3 wasn't connected?). The 3 has been charging at 48A. I don't see it limiting to 40A. So not straight 40A/40A, but not maxing out for the X either.

It sounds like there are a ton of edge cases with the dual (or triple or quad) Wall Connector setups.

Conceptually it makes sense that if multiple vehicles want to charge then the total power should be split between them equally. And if a vehicle is full but still plugged in it makes sense that the wall connector still needs to provide a minimum amount to the car (zero is not an option probably in the spec). The concept of charging whichever has a lower battery more seems silly and unlikely to be implemented.

It kind of sounds like when you plug in a car that needs to charge but it won’t until a scheduled time that it seems to allocate the power for it anyway even if it won’t make use of it.

 

[PhaseWhite]

I just installed 2 HPWCs on a 60A circuit last month. To test that the installation was right, I plugged in both cars and started them charging. Each car correctly pulled 24A (half of the 48A continuous that the circuit can handle). Then I clicked "Stop Charging" on one car but left it plugged in and the other car ramped up to 48A.

So, I'm seeing the correct load sharing behavior. This is with S and X as the two cars, maybe a 3 does something differently.

Thanks for the replies all. And @csanders90D thanks. I'm going to try this and report back to see if I can get it to ramp up by starting both, then stopping one...

To clarify what happens now is even though one car is not charging, both cars are limited to 6kw out of 12kw as long as the plug is plugged in. I had speculated the issue is being caused by the Model 3's charging port behavior since the latest software update the charge port does not lock the connector and the light does not turn on so it may not be communicating to the charger.

Turning it off/on might fix this.