Worth the breaker upgrade? 40A->50A

[awdpilot]

I picked up my 3P on 11/30 and currently I have the home charger hard-wired on a 40A circuit, so I'm charging at 32A every night.

The wire from the panel is a 6 gauge, which is capable of 50A, would it be worth it to have the breaker upgraded so that I could charge the car at 40A instead of 32?

Not sure which would be more "efficient" from a power consumption point of view.

 

[Watts_Up]

"If it ain't broke, don't fix it"...

Unless you don't have enough time to charge during your 'off peak' rate,
or need to fully charge two cars the same night, I don't see the advantage of this minor update.

I doubt you could measure any efficiency change. I charge using a 30 A (24 A nominal)
and comparing the value displayed by the power meter I installed next to my charger
and the value displayed inside the car, the charging efficiency is around 85%.

Note: I'm in CA and since you are im MA, I am curious what kind of heating you are using for your home,
and in particular water heating, as I am considering installing a water heat pump.
I think this would be more efficient and cheaper that the water gas heater that I am using.

 

[Sophias_dad]

I picked up my 3P on 11/30 and currently I have the home charger hard-wired on a 40A circuit, so I'm charging at 32A every night.

The wire from the panel is a 6 gauge, which is capable of 50A, would it be worth it to have the breaker upgraded so that I could charge the car at 40A instead of 32?

Not sure which would be more "efficient" from a power consumption point of view.

TBH, you could just turn up the charger as if it has a 50 amp breaker. If the 40 amp breaker is in your 60F basement and not flanked by other high-load breakers, it may well not trip. If it does trip, then a breaker replacement would stop the tripping. If you weren't doing the work yourself, I'd suggest just not making the breaker upgrade unless you really need that extra 8 amps. If the wire is conductors-in-conduit, you could even go to a 60 amp breaker and 48 amp charging.

Side note: I'm running 48 amps out of my 50 amp breaker for hours on end not far from you, and its never tripped.

 

[jjrandorin]

I picked up my 3P on 11/30 and currently I have the home charger hard-wired on a 40A circuit, so I'm charging at 32A every night.

The wire from the panel is a 6 gauge, which is capable of 50A, would it be worth it to have the breaker upgraded so that I could charge the car at 40A instead of 32?

Not sure which would be more "efficient" from a power consumption point of view.

Whether its worth it or not depends on whether you have ever found yourself waiting for the car to charge for something (or, if you are like me and just have a tendency to want "the fastest I can get it setup with").

From an efficiency standpoint I dont think it makes any difference whatsoever between 32amps and 40amps (or 48amps). It would make a difference if you were trying to get your daily charging into a specific time of use window, and are not able to do that currently, or if you were driving so much that your car was still charging when you were ready to go.

Other than that, its just "I want it" which is absolutely fine, too.

 

[davewill]

I'd do it just against the off chance that I find myself at home with a low battery, wanting to leave quickly. It has no significant effect on efficiency or battery longevity. That said, I've been limited to 30a at home for over a decade and never felt the need for more.

 

[awdpilot]

Fair enough, was just asking to see if there was any documented efficiencies, we have town electric with no time windows (and cheap electric, .146/kWh)

I don't have any issues with time at this point, so I guess I'll just leave well enough alone.

@Watts_Up we have an electric hot water heater.

 

[ATPMSD]

The wire from the panel is a 6 gauge, which is capable of 50A, would it be worth it to have the breaker upgraded so that I could charge the car at 40A instead of 32?

Short answer is YES! Swapping out the 40A breaker for 50A should run you about $15 and then you can configure the wall connector for a 50A circuit and charge at 40A. I might dig a little deeper first to understand why a 40A circuit was used in the first place. Maybe the service to the house is limited and a 40A circuit is all it will support?

Note that if the wire is #6 romex you CANNOT upgrade to a 60A circuit and then charge at 48A, period. A continuous load cannot exceed 80% of the wire rating. #6 romex is rated at 55A and 80% equals 44A, which is lower than the 48A than the wall connector uses when set to a 60A circuit.

 

[3sr+buyer]

From an efficiency standpoint I dont think it makes any difference whatsoever between 32amps and 40amps (or 48amps).

Wouldn't higher AC charging rates be more efficient because the car is not "turned on" for as long while charging? The car consumes a few hundred watts while it is "on".

However, this is more noticeable when charging at the slowest rates like 120V 12A, where the consumption from being "turned on" is a greater percentage of the amount delivered while charging.

 

[Braumin]

Wouldn't higher AC charging rates be more efficient because the car is not "turned on" for as long while charging? The car consumes a few hundred watts while it is "on".

However, this is more noticeable when charging at the slowest rates like 120V 12A, where the consumption from being "turned on" is a greater percentage of the amount delivered while charging.

Yes but the difference is not going to be massive

 

[SageBrush]

Wouldn't higher AC charging rates be more efficient because the car is not "turned on" for as long while charging? The car consumes a few hundred watts while it is "on".

Yes, but on the other hand there are more I^2*R losses from the higher current. The net difference is minor.

 

[pikeman]

I’m not an electrician, and there is no way I’m going to mess with changing out a circuit breaker in the main cabinet. When I had my Tesal wall charger installed I talked with the electrician about the hazards of removal and replacement of a CB on the hot bus. He said “Oh, it’s no problem!” But the new breaker resisted the initial motion of removal and surprised him. At that point I said he didn’t need to go any further. This guy wasn’t inexperienced.
Bottom line, Im not messing with a hot 100 amp buss.

 

[Watts_Up]

Not sure which would be more "efficient" from a power consumption point of view.

I would recommend adding a separate Power meter , next to the circuit breaker or the receptacle,
if you want to monitor the consumption, or determine the efficiency of the charging.
(You might need a box to hold it)

 

[SageBrush]

I’m not an electrician,

Bottom line, Im not messing with a hot 100 amp buss.

The bus is de-energized first.

 

[Sophias_dad]

Bottom line, Im not messing with a hot 100 amp buss.

You could just flip the main breaker off, then your bus bars will not be hot. If the main is in the same panel, you still have to be careful about the main supply lugs.

But by all means if you are not at ease with it, don't do it!

 

[pikeman]

The bus is de-energized first.

The only way to de-energize my panel is to remove the meter. That’s three days without electricity in my area before they return and reinstall it. That’s not an option.

 

[pikeman]

You could just flip the main breaker off, then your bus bars will not be hot. If the main is in the same panel, you still have to be careful about the main supply lugs.

But by all means if you are not at ease with it, don't do it!

The mains control the power to my distribution panel in the garage. My charger is on the main panel which is only turned off by removing the meter. And yes, I am not messing with that!

 

[SageBrush]

The only way to de-energize my panel is to remove the meter.

I said the bus, not the panel.

 

[ATPMSD]

And yes, I am not messing with that!

Given your level of knowledge I agree, stay away from the panel.

 

[DayTrippin]

I have a 60 amp circuit (for the wall charger) and a Nema 14-50 for the portable charge (which maxes at 32 amps). I charge the S off the wall charger and the 3 off the Nema.

When I am in a real hurry for the 3, I use the wall charger. I definitely notice the difference but it is 50% faster. I use it more when I need a quick turnaround and make sure I have enough juice to get out and back without a supercharger visit. I'd say 95% of the time, the 32amp charging rate is more than adequate for my 3. For my S it totally sucks TBH.

The one advantage I haven't seen anyone talk about is the ability to still charge quickly while using climate control to heat/cool the car. That is something I find very useful. The hotter or colder it is, the more this will make a difference.

In my normal daily driving situations, the 32 amp mobile charge has almost always been fine and can easily recharge the car overnight. It is when I have unexpected events that prompt me to plug the 3 into the wall charger. I have also found that by having the faster charger available, I can keep the state of charge lower (and charge quickly) which does reduce battery degradation.

 

[SageBrush]

For my S it totally sucks TBH.

How about some context of how you use the car ?
200 miles a day would be very different than 50 miles.