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What are your experiences sharing a home charger between two cars

TheRFMan

Member
Dec 15, 2019
543
390
Ottawa, Canada
I'm looking for your experience/advice/anecdotes regarding sharing a single charger between two vehicles.

I currently have a 2012 Chevrolet Volt that works well and that I plan to keep for a few more years. I will be adding a Model 3 in the next 6 months or so (depending on the COVID situation, battery day announcements and general ordering delays). However, with winter coming, my window to make electrical changes relatively easily in my uninsulated garage is closing quickly, so I'm considering what my charging setup might need to be for spring.

I currently have a NEMA 14-50 outlet and a 32A J1772 charger that I use for the Volt. The Volt can only draw 14.5A, but I put in the 32A one knowing that whatever replaces it would likely be able to use 32A. What I hadn't considered is the possibility of adding a new EV and keeping the Volt, but that's likely how things will play out for a number of reasons.

I was wondering if anyone here shares a charger between two cars. The Volt, being a PHEV with a small battery, pretty much needs to be plugged in 3 to 4 hours each evening/night. The Tesla could likely go 3-4 days between charges, but that still means that once or twice a week, the Volt would need 3-4 hours and the Tesla about 8 hours. We have time-of-use pricing here, and electricity is half price between 7PM and 7AM weekdays (and all day long on weekends), so I try to charge in those cheap time windows.

It seems like that would mean having to go out before bed a few times per week to switch the charger from the Volt to the Tesla. Not bad in summer, but not fun at all in winter at -15C with snow on the ground. I also lose the benefit of pre-heating the cabin from AC power for whichever car isn't plugged in in the morning.

I'm considering adding a 20A 240V circuit with a NEMA 6-20 outlet to add a second 16A J1772 charger for the Volt (My electrical service can't handle two 32A circuits for charging). There's a good chance the Volt will get replaced by another PHEV when it dies, so it will still be useful. Is it worth the trouble, or should I just share the charger I already have?
 

arnolddeleon

Supporting Member
Jul 21, 2012
799
864
SF Bay Area
20A 240V is a pretty good solution, it allows you to pull the most power out your setup without upgrading service. You are probably the only one who can really weigh the downside of sharing. It is certainly possibly to share a single plug.

An alternative is to look into power sharing EVSE stations (JuiceBox, ClipperCreek are examples). If you had an all Tesla fleet the HWPC can also do this. The EVSEs That will let you plug in both vehicles. They split the power if both vehicles are charging but will give it all to one if it is the only calling for power.
 

pb2000

Member
Dec 22, 2019
220
245
Calgary
How easy is it to pull another wire and what gauge is on the existing 14-50? If it's an easy run, go for the second 6-20, but otherwise you could put a sub panel on the existing circuit and break it out to a pair of 20A circuits (#8) or a 40A and 15A (#6).
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,271
7,324
Boise, ID
The convenience of being able to just leave things plugged in I think will be worth it, even if one of the vehicles has to use a much lower power connection. So I would say the Volt could even go on an available 120V wall outlet, which should generally take care of it fine with as small as its battery is.
 

TheRFMan

Member
Dec 15, 2019
543
390
Ottawa, Canada
How easy is it to pull another wire and what gauge is on the existing 14-50? If it's an easy run, go for the second 6-20, but otherwise you could put a sub panel on the existing circuit and break it out to a pair of 20A circuits (#8) or a 40A and 15A (#6).

It's a pretty easy run from the panel to the garage (about 35ft through an unfinished basement and garage). I have 6/3 Romex feeding the 14-50 outlet on a 50A breaker. The wire is only rated to 55A and as far as I know, I can't get a 55A breaker, so I pretty much consider it a 50A max circuit.

Running the wire for the additional 6-20 would be easier and cheaper than a sub-panel for sure.
 

pb2000

Member
Dec 22, 2019
220
245
Calgary
You'd never be pulling more than 44A, so the 50A breaker would probably be fine. It's a moot point though, as it's much cheaper and easier to just run a new 20A circuit.
 

patrick40363

Active Member
Mar 25, 2014
1,167
568
Cali
I'm looking for your experience/advice/anecdotes regarding sharing a single charger between two vehicles.

I currently have a 2012 Chevrolet Volt that works well and that I plan to keep for a few more years. I will be adding a Model 3 in the next 6 months or so (depending on the COVID situation, battery day announcements and general ordering delays). However, with winter coming, my window to make electrical changes relatively easily in my uninsulated garage is closing quickly, so I'm considering what my charging setup might need to be for spring.

I currently have a NEMA 14-50 outlet and a 32A J1772 charger that I use for the Volt. The Volt can only draw 14.5A, but I put in the 32A one knowing that whatever replaces it would likely be able to use 32A. What I hadn't considered is the possibility of adding a new EV and keeping the Volt, but that's likely how things will play out for a number of reasons.

I was wondering if anyone here shares a charger between two cars. The Volt, being a PHEV with a small battery, pretty much needs to be plugged in 3 to 4 hours each evening/night. The Tesla could likely go 3-4 days between charges, but that still means that once or twice a week, the Volt would need 3-4 hours and the Tesla about 8 hours. We have time-of-use pricing here, and electricity is half price between 7PM and 7AM weekdays (and all day long on weekends), so I try to charge in those cheap time windows.

It seems like that would mean having to go out before bed a few times per week to switch the charger from the Volt to the Tesla. Not bad in summer, but not fun at all in winter at -15C with snow on the ground. I also lose the benefit of pre-heating the cabin from AC power for whichever car isn't plugged in in the morning.

I'm considering adding a 20A 240V circuit with a NEMA 6-20 outlet to add a second 16A J1772 charger for the Volt (My electrical service can't handle two 32A circuits for charging). There's a good chance the Volt will get replaced by another PHEV when it dies, so it will still be useful. Is it worth the trouble, or should I just share the charger I already have?
I had a 2012 Volt and installed a 40amp unit. I had it installed in between the 2 cars in the garage. I now have a model S and 3 and share the unit for both cars. 25 ft cord so no issues.
 

Bet TSLA

Active Member
Dec 8, 2014
2,845
10,499
Cupertino, CA
Charging two Teslas off of one NEMA 14-50 has been working fine for me for a few years. But I don't need to charge either every day, and I don't need to think about cabin heating in the morning. If I were you I'd put in one of the power sharing stations that Arnold mentions. If I were trying to minimize expenditures, I'd try using what I have for a while and seeing how it works for me. Might be fine despite your reservations.
 

heems

Member
Jan 10, 2011
313
267
San Diego
We have a single Tesla wall charger on a 60A circuit. We just switch parking locations between the 2 cars (whoever gets to <30% first which tends to be the SR+). I suppose it's an "inconvenience" to have to switch park locations (move one car out, park the other in, and then put the first car in place of the other) but it happens maybe once a week or twice at most. Didn't think that was worth the money to pull in a second circuit. That's just me though - luxury is a subjective thing.
 

TheRFMan

Member
Dec 15, 2019
543
390
Ottawa, Canada
The convenience of being able to just leave things plugged in I think will be worth it, even if one of the vehicles has to use a much lower power connection. So I would say the Volt could even go on an available 120V wall outlet, which should generally take care of it fine with as small as its battery is.

That's a good point. We charged the Volt on 120V for a few years before we had the 14-50 outlet, and it worked fairly well. Unless we were out quite late on a cold winter night, we could usually get a full charge by the morning. I may end up doing that initially and saving myself some trouble. I takes about the same time to charge the Volt on [email protected] than it does to charge a LR M3 at [email protected]
 

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