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Wall Connector Power Sharing

I have 2 wall connectors behind a 60 amp service to the garage. If you plug a car in to either wall connector it will charge at 48 amp all day without issues.
If you plug two cars in at the same time they will each charge at 24 amp just fine.

However, when one of the two cars finishes but is still plugged in, the other car takes forever to ramp up to 48 amp, and constantly drops back down to 24 and begins ramping again.
The only way we’ve found to allow it to hold 48amp steady is to unplug the non charging car.

Is this normal? It’s causing the final car to charge much slower overall, and pretty annoying… seriously just considering another 60 amp line to the garage so both can pull full speed regardless..

Is there something wrong or needs to be adjusted? Or is this normal operation?
 

Rocky_H

Well-Known Member
Feb 19, 2015
8,161
10,428
Boise, ID
I can't answer this directly because I don't have a sharing configuration, but I know people are going to ask this, so I'll preemptively try to get this information from you:
I have 2 wall connectors
What type? There was the older Gen1 and Gen2, which were mostly the same, and then there was the vastly different Gen3 that is smaller and uses wi-fi to communicate. That would help people answer if they knew what you were using, because their sharing methods are kind of different.
 
I Do not have an answer but a similar problem! When both cars plugged in the one that actually charges does so at half the normal rate, even while the other one is not charging at all. If I unplug one of them then it charges at the normal rate. This is with two generation three chargers connected by Wi-Fi
 

ATPMSD

Active Member
Mar 12, 2021
1,460
1,372
Atlanta, GA
This does not seem normal:

The charge current available to my car keeps changing - is this normal?

Yes. Power sharing works by allowing all available current to be distributed as efficiently as possible based on the actual current drawn by each vehicle.

You may wish to double check your configuration / settings:

 
I let my electrician contact Tesla support, and they responded that it's how power sharing works.

The chargers do not have enough intelligence to measure how much the car is really charging or if it stops charging and thus distribute the rest of the power to the car that is still charging. You have to unplug the other car to get maximum output.

That really limits the benefits of this...
I always plug in both Teslas, but that means they will always charge at half the speed. Stupid.
 

Rocky_H

Well-Known Member
Feb 19, 2015
8,161
10,428
Boise, ID
The chargers do not have enough intelligence to measure how much the car is really charging or if it stops charging and thus distribute the rest of the power to the car that is still charging. You have to unplug the other car to get maximum output.
That's pretty strange the Tesla rep would say that, because it used to do that. It doesn't even need to communicate with the car for that. The wall connectors can monitor and report their own output current, and if some are not sending any current, they can tell that to the others, so they can increase their current output.

There was some early pie in the sky stuff about them reading the cars' state of charge and sending more to the emptier ones, but I don't think that ever worked. But this simple thing has worked in the past, where the ones that are still running can send more current if others are not running at all.
 
reading the cars' state of charge and sending more to the emptier ones
I always thought power sharing was supposed to work this way by design, but apparently not!

Yesterday we had to charge both Teslas (MYLR and M3SR+). I noticed both were charging at 30A although I have two 60A breakers in a breaker box (one for each wall charger) linked to another 60A breaker in my main panel. Obviously something was really off 😱 so I went into the leader power wall configuration and decreased the max output to 48A. Right after, both cars were charging at 24A although my MY was at a much lower SoC than my M3... So I guess intelligent power sharing is not that smart after all.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
8,161
10,428
Boise, ID
I always thought power sharing was supposed to work this way by design, [...] So I guess intelligent power sharing is not that smart after all.
I don't know if I would say by "design". More like by "PR sales advertising verbiage". That is a feature that Tesla said it would have a long time ago, but I don't think I ever heard of that working in the actual product, so it seems that was not really enabled into the design.

I noticed both were charging at 30A although I have two 60A breakers in a breaker box (one for each wall charger) linked to another 60A breaker in my main panel. Obviously something was really off
Oh, yeah, that's not good in the configuration somewhere. That would be pulling 60A on the main 60A feeder circuit, and it's not supposed to use 100% like that. That's good that you got it corrected.
 
Yes, same here. I need to unplug the other car to be able to use max rate. It never ramps up, just stays at half. This can't be by design, can it?
The setup at my parents’ house will allow a car to use upto 48A even if more than one car is plugged in. But it doesn’t seem to prioritize lower state of charge cars (usually split evenly or pretty close to it) when both are charging.

The caveat is if the charged car wakes up for whatever reason and pulls current for whatever reason, then both instantly drop to half the max rate and it takes a while for the charging car to ramp back up to the max rate.
 
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