Any problem with two HPWC Power Sharing to charge Roadster with CAN Sr?

[pwwojcik]

Hi!

I am pretty sure this will work but I thought that I would throw it out to the group in case anyone has experience one way or the other.

Right now I have a single HPWC that I use to charge either my Model S and my Roadster 1.5. I am thinking about adding a second HPWC to the same circuit in the "Power Sharing" configuration. Because I am running off a sub-panel I can't really add another circuit. I assume the dual HPWC was really designed for two Model S (or X or 3). Does anyone know any reason that this would not work well for the Roadster using the awesome CAN Sr?

Thanks!
Paul

 

[X.l.r.8]

@hcsharp

 

[Peter.h]

I don't see how it would be an issue

 

[Curt]

I’ve experienced this a few times. It seems to work just fine. It may be disconcerting if you are using OVMS.

If the Roadster is already charging and the second vehicle plugs in on the other HPWC, you will get notices that charging has been interrupted. It always seems to restart shortly after at the new amperage, though, so it’s really not a problem.

 

[hcsharp]

Hi!

I am pretty sure this will work but I thought that I would throw it out to the group in case anyone has experience one way or the other.

Right now I have a single HPWC that I use to charge either my Model S and my Roadster 1.5. I am thinking about adding a second HPWC to the same circuit in the "Power Sharing" configuration. Because I am running off a sub-panel I can't really add another circuit. I assume the dual HPWC was really designed for two Model S (or X or 3). Does anyone know any reason that this would not work well for the Roadster using the awesome CAN Sr?

Thanks!
Paul

It works great on a load-sharing HPWC (now called TWC). It will fault when you first plug it in but if you leave it alone it will clear after a few seconds and start charging. The Roadster is good at raising and lowering the amperage.

I’ve experienced this a few times. It seems to work just fine. It may be disconcerting if you are using OVMS.

If the Roadster is already charging and the second vehicle plugs in on the other HPWC, you will get notices that charging has been interrupted. It always seems to restart shortly after at the new amperage, though, so it’s really not a problem.

That's interesting I haven't seen that behavior. My car has always responded normally to the change in amperage, whether up or down, without any interruptions in charging. I'll do some more testing.

 

[pwwojcik]

This is perfect. Thanks everyone!

And thanks again, @hcsharp , for the CAN devices!

 

[Frisco-Dad]

If the Roadster is already charging and the second vehicle plugs in on the other HPWC, you will get notices that charging has been interrupted. It always seems to restart shortly after at the new amperage, though, so it’s really not a problem.

That's interesting I haven't seen that behavior. My car has always responded normally to the change in amperage, whether up or down, without any interruptions in charging. I'll do some more testing.

I see a similar behavior. If the roadster is charging and a 2nd vehicle (Model S) plugs in to the other TWC, then the Roadster will throw a fault and stop charging. The first few times this happened, I waited a few minutes, but the roadster did not start charging again. I loaned out my CAN SR, so I won't be able to test this again until next week. My overall solution is to plug in the Model S first then plug in the roadster. I've been doing this for almost 2 years now. If I leave the roadster plugged in, the next day it will try to charge again to top off the battery. This always works fine, even if the other car is charging. But if the other car plugs in and starts charging while the roadster is charging, it will stop and not start back up again. Not a big deal at that time because the roadster is mostly full and was just trying to top off the battery.

For reference, I've got a 1.5 Roadster and a November 2015 build Model S.

The CAN SR and the load sharing protocol are great. The only annoyance I have is the charging issue I describe above.

 

[pwwojcik]

Just to circle back on this in case anyone else is curious. I had the new wall connector installed so that it is the slave and the original one is the master. I only have one data point but everything works exactly as you would hope. I plugged in the roadster and it started charging at 32 amps (where the roadster is set). When I subsequently plugged in the Model S to the other wall connector, the roadster charging dropped to 20 amps (which is half of the configured power of the master wall connector. If I notice any weird behavior I'll report back.

 

[rudholm]

I have the same experience. Two new HPC's sharing a 100A circuit, one charging a Roadster via CAN-SR, and one charging a Model 3. Works perfectly.

 

[hcsharp]

Just to circle back on this in case anyone else is curious. I had the new wall connector installed so that it is the slave and the original one is the master. I only have one data point but everything works exactly as you would hope. I plugged in the roadster and it started charging at 32 amps (where the roadster is set). When I subsequently plugged in the Model S to the other wall connector, the roadster charging dropped to 20 amps (which is half of the configured power of the master wall connector. If I notice any weird behavior I'll report back.

That's been my experience as well. Plugged in the Roadster first and it was charging at 40A. Then plugged in a Model 3 and the Roadster dropped to 20A but kept charging, and the Model 3 began charging at 20A. I have a 2.5.

 

[Frisco-Dad]

The CAN SR and the load sharing protocol are great. The only annoyance I have is the charging issue I describe above.

Here's an update to my post above. The behavior of the load sharing protocol on the TWC has been changing lately. In the past I saw the power divided to each car based on SOC. The car with a higher SOC got less power, and the car with lower SOC got more power. Recently I observed that the TWC will divide the power 50/50 regardless of the SOC of either car.

On a plus note, I no longer observe the annoying charging issue with the Roadster I describe earlier.

More detailed description in another thread posted here: 2 Tesla wall connector load sharing

 

[pwwojcik]

This is how my setup is behaving. Two TWC and one Model S and one Roadster 1.5 with CAN SR.

If only one car is plugged in, it gets the full power. If both cars are plugged in, each gets half power. This is true regardless of the state of charge or even if one of the cars is finished charging. This is my situation most of the time. One car is already plugged in and I get home and plug the car that I was driving in.

To me it is working just fine. In the rare event that I want to charge quickly I do need to unplug the other car. Most of the time I am not adding a lot of charge and I am not in a rush so the half speed is OK. I am sure that would be bothersome to some people....

I love the setup. Before when I used to leave the Roadster on 120V and it would occasionally trip the GFCI circuit breaker which was a pain. I love having both cars reliably plugged in all the time.

 

[hcsharp]

If only one car is plugged in, it gets the full power. If both cars are plugged in, each gets half power. This is true regardless of the state of charge or even if one of the cars is finished charging.

That's strange. A car that's plugged in is always allocated at least 6A whether it's using it or not. The other car gets full power minus 6A, or 34A in your case. Are you sure it allocates 20A even when it's not charging?

 

[pwwojcik]

Hmmm. Interesting detail. I’ll experiment when I can to confirm what is happening and will report back.

 

[rudholm]

I have two Wall Chargers set to share 80A (on a 100A circuit). When I come home after a day or commuting with the 3, it charges at its maximum of 48A. If I come home after a day of commuting with the Roadster, it charges at its maximum of 70A. If they both need charging, they each get offered 40A until one of them starts drawing less (which happens as a car nears its charge set point). Then the other car gets offered to additional available amps.

 

[hcsharp]

I have two Wall Chargers set to share 80A (on a 100A circuit). When I come home after a day or commuting with the 3, it charges at its maximum of 48A. If I come home after a day of commuting with the Roadster, it charges at its maximum of 70A. If they both need charging, they each get offered 40A until one of them starts drawing less (which happens as a car nears its charge set point). Then the other car gets offered to additional available amps.

That's been my experience as well, except that no car ever gets allocated less than 6 amps even after it's finished charging.

 

[pwwojcik]

So maybe mine is just different or maybe I am evaluating it wrong. I have the two wall chargers set at 40 Amps (because they are on a 50 Amp circuit in my subpanel). The roadster was plugged in but had finished charging a long time ago. When I plugged in the Model S, it was allocated 20 Amps. As soon as I unplugged the roadster, the Model S jumped to 40 Amps. It seems to be the case that whenever a car is plugged in, that wall charger is allocated half of the available power.