Best Way To Install Car Charger with PowerWalls?

[ftrv8]

Hello all!

Hope you all can advise me yet again

Finally got my solar system installed after a year and half. Used a third party Tesla certified installer to get a 7.3 kWh system with two PWs.

Our next vehicle will be a BEV (haven’t decided yet).

With that said. I’ve paid the installer to install either wiring or a charger already.

With the batteries what’s the best way to install the charger? Unless it’s just one way. Is there a benefit to installing it directly into the main or after the batteries. If there is even such a thing, forgive my lack of knowledge.

Also, should I ask for max amp they can install wiring for? Not knowing what exact model of car I will be getting. I believe they mentioned they could install up to 80amps.

 

[gcsutton]

My thought process is, it depends on what you're trying to do and what you may want to do in the future. Some issues are:

1. If you are only looking to charge one Tesla now, I'd run a 60 amp dedicated circuit
2. If you want to future proof, and depending on how involved adding circuits is, run a 100 amp line. That's what I did. You can use this either for two vehicles, or one faster charging vehicle and charging system in the future.
3. Two PW is a fairly small amount of storage to even charge a car from, let alone possibly two. With only two PWs, I wouldn't bother hooking the charger up where it would draw from the PWs. The electrician should be able to put the circuit on the grid, before the Tesla gear, so it would work as if you didn't have solar, PWs, etc. If the grid is up you can charge, if grid is down, no charging without using the mobile system Tesla supplies with each car.
4. If you do hook it up where it uses the PWs, you'll have to monitor the charging, and turn off PW use when there is no grid or solar, as charging a car from the PWs at 11kW/hour would completely drain the batteries in about 2 hours and only charge the car about 25%-30% when solar isn't producing.

 

[jjrandorin]

It depends on what car charger, and car, and whether you are "OK" with the idea that your future BEV might charge in the middle of the night during a power outage, and drain your two powerwalls.

Given that you do not know what BEV you might be getting, nor when you might get it, I would say that the "safest" thing to do would be to have a 240V 14-50 outlet (plug) installed on the NON backup side. Buying an outlet vs a wall connector will let you plug in a variety of brands fairly easily, yet also put the wiring in place in case you want to swap to a wall connector "later" when you know which vehicle you want, and decide that you want charging different than it comes with.

If you knew for a fact you were going to get a tesla, tesla has some amount of integration in that it has a setting to not drain your powerwalls if there is a power outage. No guarantee any other BEV will do that with powerwalls.

 

[holeydonut]

I think you shouldn't plan your system around the fear of an BEV draining the Powerwalls in the event of an outage. This event is such a small fraction of likely outcomes that you give up a lot of pros of having the EV being charged on the backup side.

For example if you put your EV charger on the backup side...

1) If you lose power for a long-duration of time, then you'll be able to use your EV to soak up extra solar production that you may lose once your Powerwalls fill up.

2) As jjrandorin pointed out with the Tesla Ecosystem then getting a Tesla will mean the vehicle will be able to "load shed" if the power goes out so you don't have to worry about accidental powerwall drainage. If you don't like Tesla vehicles consider...

3) Tesla Energy Gateway has a "load shed" 24V trigger wire that technically could be used to close a relay on any home load circuit if the power company goes offline. Basically if you could find an electrician to run a relay for your EV circuit, as long as a 24v trigger is going to the relay then the circuit is closed. But if the PoCo goes offline, the Gateway will not send the 24V to the relay and the circuit opens. Not "easy" but technically possible if you really really really want to prevent your worst-case outcome.

4) Most of the things that can cause many hours-long of unexpected shutdown in California are typically things you'll know ahead of time. If you're in a pending red flag warning, PSPS clusterf*ck, or there are storms on the forecast (haha rain? what's that)... then you can just unplug your EV or drop the charge level a bit to restrict how much it could draw overnight.

5) If you put your EV charger on the non-backup side after you have your Powerwalls in place, many electricians will have difficulty hooking up the CTs or other metering devices to let your system know the EV charger is a home load.

 

[jjrandorin]

5) If you put your EV charger on the non-backup side after you have your Powerwalls in place, many electricians will have difficulty hooking up the CTs or other metering devices to let your system know the EV charger is a home load.

Thanks for mentioning this. Because in my case, it seemed to be "very easy" for the install team to connect my EV charger on the non backed up loads side, yet have it still show as a home load, I always forget that some others have had a much different experience with this.

In my case, my Tesla wall connector is on the non backed up loads side (with a tesla energy gateway version 1), but it still shows properly in the tesla app as a home load, so when the grid is up, it can be charged with powerwall energy, solar, etc. This could be because my home had (pre powerwall) only one load center / breaker box, rated for 200 amps, so the CT configuration may not have been as difficult.

Personally, right now, I wish my wall connector was on the backed up loads side instead of the non backed up loads, because of the now current tesla integration. I had it put on the non backed up loads side, because, my personal policy when I buy something is to set it up for how it operates NOW, not how it "might operate after some firmware update the MFG promises".

Keeps me from being angry when said firmware updates take longer, or never get delivered (not just tesla). So, I didnt want to be in a situation I described above with my 2 powerwalls potentially being drained by my model 3. That is much less a concern now, so if one is in the tesla echosystem, I would recommend people put on the backup loads side.

If the plan is "BEV later at some point, we dont know when or what kind", then thats where I recommended the fairly conservative approach I did, as it has the least amount of risk (but you also may lose some potential functionality, as you mentioned).

Appreciate your take on this.

 

[ftrv8]

Thank you all! Exactly what I was looking for. So essentially backup or non backup side.
I assume backup side, I’d be able to monitor a car charging via the Tesla app?

 

[jjrandorin]

Thank you all! Exactly what I was looking for. So essentially backup or non backup side.
I assume backup side, I’d be able to monitor a car charging via the Tesla app?

well....

If I understand the question about monitoring... If the vehicle is a tesla vehicle, you would be able to see the charging status in the tesla app, in the vehicle section (and also start and stop charging via the tesla app).

If the vehicle is not a tesla, in order to see whether the car was charging in the TESLA app, you would be relying on the Current Transducers (CTs) to be installed properly in your electrical box to monitor the load of the car charging. If its on the backup loads side, assuming all your other loads show up, car charging would show up as an increase in home load (not something separate).

If its on the non backed up loads side, AND the CTs are not setup to monitor that load, then you would not see it in the tesla app (but you would certainly still be paying for the electricity).

TL ; DR -- Tesla vehicle, yes, you can see it in the app under vehicle. Non tesla vehicle "it depends on CT placement, and would show up as a home load if CTs placed to monitor it">

 

[miimura]

Personally, I have both my EV charging circuits on the non-backup side of the Tesla Gateway. So, it is impossible for my car charging to drain my Powerwalls when the grid is down. Since I have a small solar system, it is very unlikely that I would have extra energy for EV charging anyway. If I did, plugging a car into a 120V outlet that is on the backup side would be sufficient to soak up the small amount of extra energy.

When the grid is up, my Powerwalls measure all consumption, so when using Time Based Control, they will allow the EV charging to come from the grid during Off-Peak but would send Powerwall energy to the car if it was charging during Peak hours. Some Powerwall systems are installed so that they don't measure the non-backup loads, but IMHO this is an improper installation.

If you get a Tesla vehicle, there is an option in the app to only allow the car to charge off-grid when the Powerwalls are above a given state of charge percentage.

 

[h2ofun]

Just never understand why this seems to be so hard. My setup is full home, no non backup stuff. I am planning to run a 100amp subpanel into my garage. Then thinking of install 3 gen3 tesla charges, which can balance I believe between them. And all this worry about when the power goes out. Well, when the power goes out, folks need to change their behaviors. It usually does not go out for long. AND, I am SO glad I have ICE cars.

 

[holeydonut]

Just never understand why this seems to be so hard. My setup is full home, no non backup stuff. I am planning to run a 100amp subpanel into my garage. Then thinking of install 3 gen3 tesla charges, which can balance I believe between them. And all this worry about when the power goes out. Well, when the power goes out, folks need to change their behaviors. It usually does not go out for long. AND, I am SO glad I have ICE cars.

Dude you have 5 Powerwalls. It's like you're Scrooge McDuck asking why some people struggle to pay for food haha. Normal Powerwall customers have that tough call to make on their EV circuit placement since they don't have mega Powerwalls or people like @Vines designing their systems.

 

[ftrv8]

Dude you have 5 Powerwalls. It's like you're Scrooge McDuck asking why some people struggle to pay for food haha. Normal Powerwall customers have that tough call to make on their EV circuit placement since they don't have mega Powerwalls or people like @Vines designing their systems.

5 PWs!! Gluttony!

 

[Tim-in-CA]

 

[arnolddeleon]

II would recommend the simple configuration of putting everything on the backup side. If everything is behind the Powerwall most people would understand the basic idea of managing loads whether that is car charging or air conditioning or an electric cooktop. This is further simplified by the increased power capability in the current versions of the Powerwall.

When I first got my Powerwalls I thought I made mistake in putting everything on backup side. I was worried about car charging emptying the battery. I've since changed my mind. I realized how unlikely the emptying the battery scenario with car charging was. Even if happened it was pretty easy to recover from. It will be more likely in a grid down situation that I would want to charge the car (possibly with excess production).

Since the original poster (OP) has two Powerwalls I definitely recommend just backing everything up.

 

[ftrv8]

Yes sir. Going the backup side. So far everything is on the backup even AC. My area of CA we hardly get blackouts. Not worried about prolonged blackouts.

 

[bryan995]

I have two chargers, one within the whole house backup that can pull from PWs and the other connected directly to the grid, ahead of the gateway (un-monitored at the moment).

Normally I only ever charge from the grid-charger. The second one (using mobile charger w/ 14-50 plug) enables the ability to a) charge the car when grid is down b) shed excess solar production into the vehicles keeping solar active for longer

 

[jboy210]

We have a full house backup setup that includes the vehicle charger. We usually wait to charge until it is daylight and can refill the Powerwalls with solar production.

 

[sunwarriors]

I opted to not backup the 14-50 outlet since it's just not feasable to use that in my case with only 2 Enphase batteries with how large car batteries are.

Worst case scenario for me is to simply plug any charger into a regular L1 120V 15/20 amp circuit instead and get the poor slow charge rates. I assume during massive power outages, most people won't be expected to drive many places (or use that as an excuse to just WFH if you're expected to go to the office ).

 

[Zorg]

Backed up our 2 Gen2 chargers with our 2 PWs. The chargers are one circuit and can load share as necessary. I like to have the option to charge the cars in case of a long outage, not that I expect it to be the case here until we get a big earthquake and we're out of power for days.

 

[gpez]

I opted to not backup the 14-50 outlet since it's just not feasable to use that in my case with only 2 Enphase batteries with how large car batteries are.

Worst case scenario for me is to simply plug any charger into a regular L1 120V 15/20 amp circuit instead and get the poor slow charge rates. I assume during massive power outages, most people won't be expected to drive many places (or use that as an excuse to just WFH if you're expected to go to the office ).

This is exactly what I have configured. My L2 EV charger (14-50) is not backed up but there are 120v 15a garage circuits that are for L1 charging (120v at 8a or 12a).

 

[zƬesla]

How difficult is it to have it on the backed up side and be able to control whether to charge or not if grid is down? Thinking it would be nice to charge with excess solar if grid is down but be able to not drain battery. Sounds like Tesla EV does this but looking for a general solution.