Home charging on a 35A circuit...

[eevee-fan]

I think it runs the cooling pump any time any charging is underway. So yeah, generally I agree that lower charge rates are good, but I think there are limits to it. The pump having to run longer is my main concern.

I hear your concern so I did a search... seems at 120v 15a charging, the pump does not need to run.So, 240v 5a (while would be the wattage equivalent of 120v 10a), it should also not run. YMMV.

How many miles per hour for a charge on a 110 volt outlet for Model S60

 

[focher]

Charging at lower ratings does nothing good. It just increases losses. The car is engineered for the higher rates. If you have them, use them.

 

[eprosenx]

I hear your concern so I did a search... seems at 120v 15a charging, the pump does not need to run.So, 240v 5a (while would be the wattage equivalent of 120v 10a), it should also not run. YMMV.

How many miles per hour for a charge on a 110 volt outlet for Model S60

Hrm, this is the first I heard of that. Very interesting if true! Of course this could vary by car model and by software rev.

My opinion may change slightly if this is true (not having to run the pump), but still, I see no issues with charging up to the rated rates. I wonder what triggers the pump. Maybe all 120v charging does not run it but all 240v charging does? (Hopefully not, hopefully it would be temperature based, but the temp sensors may not work without the circulating pump running)

It might be interesting if we could figure out a way to charge at the max rate possible, but just under the threshold where the pump needs to come on. That might be efficient especially if at 240v. But this also assumes the battery is not cold and having to be kept warm to charge. Keeping it warm for hours on end to charge would be really inefficient.

 

[Tessaract]

If everything (receptacle, wiring, breaker) is rated for at least 30A and you'll only be drawing a 24A continuous load, you should be good as long as it is wired up properly.

35A is odd. Wiring support more by chance? If it did and you had capacity, you could bump up the breaker and receptacle.

Of course, you should probably also consult an electrician to be sure.

I agree that a 35A breaker is quite odd. A possible reason for this is that a house load calculation showed that a larger service ampacity would be required for a larger EV circuit, so the electrician "squeezed in" the most that the load calculation would allow for the existing service size. I had to upgrade my service from 100A to 200A to add my 60A EV charging circuit, but might not have need the service upgrade for a 35A EV circuit.
I also agree with the advice to check with an electrician if the wire gauge and service load calculation would support more than 35A. If so, a simple breaker change would increase your charging capability.

 

[eprosenx]

I agree that a 35A breaker is quite odd. A possible reason for this is that a house load calculation showed that a larger service ampacity would be required for a larger EV circuit, so the electrician "squeezed in" the most that the load calculation would allow for the existing service size. I had to upgrade my service from 100A to 200A to add my 60A EV charging circuit, but might not have need the service upgrade for a 35A EV circuit.
I also agree with the advice to check with an electrician if the wire gauge and service load calculation would support more than 35A. If so, a simple breaker change would increase your charging capability.

FWIW it is unlikely that a 35a breaker was done for load calculation reasons since breaker size has nothing to do with load calculation (the nameplate value of the device being connected is what matters). I am not aware of any EVSE’s that draw 80% of 35 amps. I only know of devices that draw 24 amps which is 80% of 30a.

But the load calculation is a good topic to bring up! I wanted to bottom out on what kind of wire is available first before getting to that stage of the conversation. Hopefully a recently built house has some extra capacity.

 

[jjrandorin]

Uh, my car warned me specifically about charging to 90% after a couple times, so at least my LR Model 3 built in Sep 2018 did in fact display a warning not too long ago. Maybe it has changed, but there you have it. I believe what the car displayed on its screen more than someone on the internet, but do what you like.

I do agree that most charging discussions are overthinking it, especially L2 charging.

It warns you if you charge to 91% or more, not 90% (at least no my model 3P built in dec 2018.)

 

[mswlogo]

I hear your concern so I did a search... seems at 120v 15a charging, the pump does not need to run.So, 240v 5a (while would be the wattage equivalent of 120v 10a), it should also not run. YMMV.

How many miles per hour for a charge on a 110 volt outlet for Model S60

Any time the car is awake it can use a fair amount of power. Sentry Mode for example is known to use about 1-2 miles per hour. This is ignoring the pumps.

Charging at 5A as suggested is like 3 miles per hour on a Model S.

So for every hour you put 3 miles in you lose 1-2. Great advice you gave your friend.

 

[eevee-fan]

Any time the car is awake it can use a fair amount of power. Sentry Mode for example is known to use about 1-2 miles per hour. This is ignoring the pumps.

Charging at 5A as suggested is like 3 miles per hour on a Model S.

So for every hour you put 3 miles in you lose 1-2. Great advice you gave your friend.

Well, then good thing you did not talk him into enabling sentry mode while charging in the garage.

His round trip commute is 2 miles.

 

[Tessaract]

FWIW it is unlikely that a 35a breaker was done for load calculation reasons since breaker size has nothing to do with load calculation (the nameplate value of the device being connected is what matters). I am not aware of any EVSE’s that draw 80% of 35 amps. I only know of devices that draw 24 amps which is 80% of 30a.

But the load calculation is a good topic to bring up! I wanted to bottom out on what kind of wire is available first before getting to that stage of the conversation. Hopefully a recently built house has some extra capacity.

Could still be done for load calculation reasons. An EV is not a fixed load, but a configurable load. For example, the HPWC can be configured to supply 28A to the vehicle, which corresponds to a 35A breaker. In this case, 28A is the load. If maximum nameplate were the only consideration, then every HPWC would have to be included in load calculation at 80A, and many EV installations would be non-compliant. And no house with less than a 200A service would stand any chance of being able to support an HPWC.

 

[eprosenx]

Could still be done for load calculation reasons. An EV is not a fixed load, but a configurable load. For example, the HPWC can be configured to supply 28A to the vehicle, which corresponds to a 35A breaker. In this case, 28A is the load. If maximum nameplate were the only consideration, then every HPWC would have to be included in load calculation at 80A, and many EV installations would be non-compliant. And no house with less than a 200A service would stand any chance of being able to support an HPWC.

Hah, I forgot that the Wall Connector had a 35a setting. Regardless though, on a wall connector, the ampacity of the circuit does not matter at all. What matters is what the rotary dial is set to. Nothing more. You can hook the Wall connector to a 60a circuit (as long as the wire has sufficient ampacity) and set it to the 50/40a setting and the load will be calculated as if it is a 40a continuous load.

Similarly, you can plug the UMC gen 2 into a NEMA 14-50 on a 50a circuit and it is calculated as 32a continuous since that is the load to be served. If you use the 14-30 UMC adapter you calculate the load as 24 amps continuous.

Nowhere in the load calculations do they care what the breaker ampacity is. It only matters what the load to be served is.

 

[Tessaract]

Hah, I forgot that the Wall Connector had a 35a setting. Regardless though, on a wall connector, the ampacity of the circuit does not matter at all. What matters is what the rotary dial is set to. Nothing more. You can hook the Wall connector to a 60a circuit (as long as the wire has sufficient ampacity) and set it to the 50/40a setting and the load will be calculated as if it is a 40a continuous load.

Similarly, you can plug the UMC gen 2 into a NEMA 14-50 on a 50a circuit and it is calculated as 32a continuous since that is the load to be served. If you use the 14-30 UMC adapter you calculate the load as 24 amps continuous.

Nowhere in the load calculations do they care what the breaker ampacity is. It only matters what the load to be served is.

Yes. I was suggesting, though, that possibly a 35A breaker had been chosen because that's was the total remaining load capacity, according to a load calculation. Naturally, the cable gauge needs to support this ampacity, but it's likely the cable could support more, and that would be an interesting data point, since that means that if more load capacity were created (larger service, etc.) then a connected HPWC could also be "dialed up" to a higher setting.

 

[mswlogo]

Well, then good thing you did not talk him into enabling sentry mode while charging in the garage.

His round trip commute is 2 miles.

Then I’d tell him to charge once a week at a “normal” rate. And probably set his target to 70%.

My commute is only 10 miles round trip and charge once or twice a week to 80%.