What Wall Charger to Buy???

[SwampNut]

I installed a UMC outlet for a friend sharing the dryer's 50a outlet. Car charges after 11:30, he is in bed well before 10 as if his life depends on it. But yeah, everyone has a slightly different situation. Most people fall into a range where they need more than 120v/12a, but not 240v/50a. Heck even a 240v/20a would be a huge leap over 120v.

My business associate with the Leaf confirmed he uses a 120v outlet, but drives very little and of course the battery is pretty small.

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[Crissa]

Those SplitVolt adaptors cost $380… barely less than the Wall Connector. You would likely need to install that with a GFCI breaker. Plus you need a UMC for each vehicle. Now you’ve spent more money and it’s not nearly as nice as having 2 Wall Connectors that cooperate.

The wall box doesn't split the outlets? I don't understand why you replied to that?

-Crissa

 

[Crissa]

Most people fall into a range where they need more...

I have repeatedly pointed out that this is untrue.

Median miles are below what you can easily get with a 120/15a outlet.

-Crissa

 

[SwampNut]

Several of us have repeatedly pointed out that median miles mean nothing.

How about this: I don't know one single person with a Tesla who never needs more than 120v charging.

 

[Crissa]

How about this: I don't know one single person with a Tesla who never needs more than 120v charging.

Is that a personal incredulity or anecdotal fallacy?

Also, I never said they wouldn't. Any night away from home they clearly couldn't charge there. And as an anecdote, I pointed out my miles away from home account to about a third of my total miles.

Which only makes the Level 1 charger better.

-Crissa

 

[SwampNut]

Is that a personal incredulity or anecdotal?

Yes.

Most people need more than 120v charging.

 

[RMK!]

I installed a Tesla Wall charger and our 2 Tesla share the one charger. The Cybertruck will use that charger when I get it next year (oops, I let the cat out of the bag).

Overnight charging is easy and at 40+ miles gained per hour of charging we only Supercharge on road trips. In fact, I'm going to have to make a concerted effort to use the 3000 miles of Supercharging we received with the cars before they expire this year.

Too bad they stopped that program but under the current circumstances, I understand.

Current Tesla Safety Score is 93 without even trying ...

 

[Balthezor]

The wall box doesn't split the outlets? I don't understand why you replied to that?

-Crissa

We forgetting the cost of copper and putting holes in the walls? Not as easy to put in a second wall connector.

 

[HaulingAss]

A battery isn't considered cycled until it goes below 50.

And as pointed out, even at 350Wh/mi that's over 11k miles per plugged in 8 hours a day. That's more than enough for the average driver, even with some battery heating or cooling from the wall.

Cars on average spend 95% of the time parked. The median commute is 41 miles. Stay plugged in twelve hours out of the day on average and you have over 3k of extra miles charged per year, assuming no days off.

Don't underestimate the lowly Level 1 charge point.

-Crissa

I'm not under-estimating the lowly Level 1 charge circuit, I lived with one through an entire winter. And it was not fun. It won't work for many people. And that was with one of the most efficient EV's, a Model 3 with Aero wheels. The Cybertruck will be much more challenging.

Remember this important fact: Averages are only that - averages. Not every week is average. When you have one of those not average weeks you will regret being handicapped with only 120V and 15 amps.

The other fact is your electrical bill will be lower if you can charge near the top of the power curve for whatever charger your EV has built in. Most Tesla have chargers that can utilize 240 volts and 48 amps for the most efficient home charging. The Cybertruck will be able to accept at least 48 amps.

If at all possible, shoot for a minimum of 240 volts and 30 amps. If not possible, yes, make do with less. Even a 20 amp 120 volt circuit is a bigger step up from a 15 amp 120 volt circuit than the numbers would suggest because of the cars electrical overhead that must be covered before the electricity starts flowing into the batteries.

 

[Crissa]

I'm not under-estimating the lowly Level 1 charge circuit, I lived with one through an entire winter. And it was not fun. It won't work for many people. ...

Remember this important fact: Averages are only that - averages. Not every week is average. When you have one of those not average weeks you will regret being handicapped with only 120V and 15 amps.

That's the thing. Most would be average. Or less. So no, most won't have a problem. You're not average. That's okay.

The other fact is your electrical bill will be lower if you can charge near the top of the power curve for whatever charger...

That's not how EV charging rectifiers work. They're not PC power supplies. They have components that work at specific power levels. The units add together to make the requested power level. A 12a (for a 15a level 1 outlet) plus a 20a makes a 32a and so you have three levels from two circuits.

So it ends up the same efficiency. (Although often they are more efficient at 240 vs 120, but that's another thing entirely.)

-Crissa

 

[ajdelange]

Remember this important fact: Averages are only that - averages. Not every week is average. When you have one of those not average weeks you will regret being handicapped with only 120V and 15 amps.

Not necessarily so. Every time my backup generator runs I regret that I bought a 48 kW sized unit when, as it turns out I could have gotten by with a much smaller unit. My reasoning on picking the larger unit was exactly what you propose. I do have loads bigger than 48 kW but they are rare and could easily be shed when on genny. In making an intelligent decision one must trade the anticipated "pain" of the regret against the anticipated "pain" of over engineering. The key word is "anticipated". You won't know if you have made the right decision until the system is installed and has been operated for some time.

The other fact is your electrical bill will be lower if you can charge near the top of the power curve for whatever charger your EV has built in.

What's the reasoning here? The only way the electric bill would be lower is if the chargers were appreciably less efficient at lower power levels. The chargers are all around 90% efficient when operated at 240 irrespective of load. They may (I've never tested it) be a bit less efficient at 120 than at 240 but it would be a matter of a % or so. So a percent or 2 of 5% (typical fraction of total household consumption represented by BEV charging - YMMV). I guess another way one could incur higher cost by charging at a lower rate would be in a situation where there is a steep discount in a narrow TOD window into which one could fit his charging if done at a high rate but not a low one.

Most Tesla have chargers that can utilize 240 volts and 48 amps for the most efficient home charging.

As noted in the last paragraph charging isn't really any more efficient at 48A than it is at 10A. Another thing to keep in mind is that faster charging is harder on the battery than slower. Thus a battery charged at 10A will have more capacity at the end of 5 years than one charged at 48. Will the difference be significant? Maybe is the best I can say.

The Cybertruck will be able to accept at least 48 amps.

True but my philosophy has always been to charge at the slowest rate possible consistent with my other goals so I typically charge at 30A. Why not? I've got the time.

The first thing many say when considering charging solutions for the CT is "It's battery is twice the size of the battery in the X. I'll need a big charger for that!" Well that's true of you are charging the CT fully every night. But you are not. You are replacing miles you used the previous day (or will use on the following day). The reason you want hefty charging for the CT is that its consumption is going to be over 400 Wh/mi (as compared to 200 - 300 for smaller vehicles). For example if you drive 100 mi per day you'll be using 40 kWh plus phantom i.e. about 44 kWh. At 90% efficiency that means close to 50 kWh from the wall. A 48A (11.5 kW) charge rate will take over 4 hrs to load that. A 30A (7.2 kW) rate around 7 and it is clear that the 120V UMC with it's paltry 1.44 kW is completely inadequate.

If at all possible, shoot for a minimum of 240 volts and 30 amps.

That seems a reasonable recommendation. It is worth examining one's particular use case to determine whether it actually is or not.

I will repeat my recommendation from an earlier post: Install a 120A sub panel near where you plan to install the EVSE. You will be able to connect two HPWC commissioned at the maximum (60A), or 4 commissioned at 30 A etc to this sub panel.

Even a 20 amp 120 volt circuit is a bigger step up from a 15 amp 120 volt circuit than the numbers would suggest because of the cars electrical overhead that must be covered before the electricity starts flowing into the batteries.

It doesn't work quite that way but it doesn't matter. The "overhead" is called "phantom drain" and is part of your daily charging load at whatever rate you charge. It can be quite high if you use utilities like TeslaFi or Stats. As I do my phantom drain amounts to 4 kWh/da. Averaged over the 24 hrs in a day that's about 170W which is a good chunk of the 1440W provided by the 120V configuration of the UMC.

Full disclosure: I charge from solar. I am motivated to keep the total garage load (most of which is, of course, BEV charging) at or below solar cell production so that a little current as possible is drawn from the building's batteries. This minimized battery round trip current and prolongs their life.

 

[HaulingAss]

Not necessarily so. Every time my backup generator runs I regret that I bought a 48 kW sized unit when, as it turns out I could have gotten by with a much smaller unit. My reasoning on picking the larger unit was exactly what you propose. I do have loads bigger than 48 kW but they are rare and could easily be shed when on genny. In making an intelligent decision one must trade the anticipated "pain" of the regret against the anticipated "pain" of over engineering. The key word is "anticipated". You won't know if you have made the right decision until the system is installed and has been operated for some time.

What's the reasoning here? The only way the electric bill would be lower is if the chargers were appreciably less efficient at lower power levels. The chargers are all around 90% efficient when operated at 240 irrespective of load. They may (I've never tested it) be a bit less efficient at 120 than at 240 but it would be a matter of a % or so. So a percent or 2 of 5% (typical fraction of total household consumption represented by BEV charging - YMMV). I guess another way one could incur higher cost by charging at a lower rate would be in a situation where there is a steep discount in a narrow TOD window into which one could fit his charging if done at a high rate but not a low one.


As noted in the last paragraph charging isn't really any more efficient at 48A than it is at 10A. Another thing to keep in mind is that faster charging is harder on the battery than slower. Thus a battery charged at 10A will have more capacity at the end of 5 years than one charged at 48. Will the difference be significant? Maybe is the best I can say.

True but my philosophy has always been to charge at the slowest rate possible consistent with my other goals so I typically charge at 30A. Why not? I've got the time.

The first thing many say when considering charging solutions for the CT is "It's battery is twice the size of the battery in the X. I'll need a big charger for that!" Well that's true of you are charging the CT fully every night. But you are not. You are replacing miles you used the previous day (or will use on the following day). The reason you want hefty charging for the CT is that its consumption is going to be over 400 Wh/mi (as compared to 200 - 300 for smaller vehicles). For example if you drive 100 mi per day you'll be using 40 kWh plus phantom i.e. about 44 kWh. At 90% efficiency that means close to 50 kWh from the wall. A 48A (11.5 kW) charge rate will take over 4 hrs to load that. A 30A (7.2 kW) rate around 7 and it is clear that the 120V UMC with it's paltry 1.44 kW is completely inadequate.




That seems a reasonable recommendation. It is worth examining one's particular use case to determine whether it actually is or not.

I will repeat my recommendation from an earlier post: Install a 120A sub panel near where you plan to install the EVSE. You will be able to connect two HPWC commissioned at the maximum (60A), or 4 commissioned at 30 A etc to this sub panel.

It doesn't work quite that way but it doesn't matter. The "overhead" is called "phantom drain" and is part of your daily charging load at whatever rate you charge. It can be quite high if you use utilities like TeslaFi or Stats. As I do my phantom drain amounts to 4 kWh/da. Averaged over the 24 hrs in a day that's about 170W which is a good chunk of the 1440W provided by the 120V configuration of the UMC.

Full disclosure: I charge from solar. I am motivated to keep the total garage load (most of which is, of course, BEV charging) at or below solar cell production so that a little current as possible is drawn from the building's batteries. This minimized battery round trip current and prolongs their life.

There is so much wrong here I don't have the time to fix it now. Let it be sufficient to let newbies know that all of the above information should not be relied upon.

 

[SwampNut]

Not necessarily so. Every time my backup generator runs I regret that I bought a 48 kW sized unit when, as it turns out I could have gotten by with a much smaller unit. My reasoning on picking the larger unit was exactly what you propose. I do have loads bigger than 48 kW but they are rare and could easily be shed when on genny. In making an intelligent decision one must trade the anticipated "pain" of the regret against the anticipated "pain" of over engineering. The key word is "anticipated". You won't know if you have made the right decision until the system is installed and has been operated for some time.

What's the reasoning here? The only way the electric bill would be lower is if the chargers were appreciably less efficient at lower power levels. The chargers are all around 90% efficient when operated at 240 irrespective of load. They may (I've never tested it) be a bit less efficient at 120 than at 240 but it would be a matter of a % or so. So a percent or 2 of 5% (typical fraction of total household consumption represented by BEV charging - YMMV). I guess another way one could incur higher cost by charging at a lower rate would be in a situation where there is a steep discount in a narrow TOD window into which one could fit his charging if done at a high rate but not a low one.


As noted in the last paragraph charging isn't really any more efficient at 48A than it is at 10A. Another thing to keep in mind is that faster charging is harder on the battery than slower. Thus a battery charged at 10A will have more capacity at the end of 5 years than one charged at 48. Will the difference be significant? Maybe is the best I can say.

True but my philosophy has always been to charge at the slowest rate possible consistent with my other goals so I typically charge at 30A. Why not? I've got the time.

The first thing many say when considering charging solutions for the CT is "It's battery is twice the size of the battery in the X. I'll need a big charger for that!" Well that's true of you are charging the CT fully every night. But you are not. You are replacing miles you used the previous day (or will use on the following day). The reason you want hefty charging for the CT is that its consumption is going to be over 400 Wh/mi (as compared to 200 - 300 for smaller vehicles). For example if you drive 100 mi per day you'll be using 40 kWh plus phantom i.e. about 44 kWh. At 90% efficiency that means close to 50 kWh from the wall. A 48A (11.5 kW) charge rate will take over 4 hrs to load that. A 30A (7.2 kW) rate around 7 and it is clear that the 120V UMC with it's paltry 1.44 kW is completely inadequate.




That seems a reasonable recommendation. It is worth examining one's particular use case to determine whether it actually is or not.

I will repeat my recommendation from an earlier post: Install a 120A sub panel near where you plan to install the EVSE. You will be able to connect two HPWC commissioned at the maximum (60A), or 4 commissioned at 30 A etc to this sub panel.

It doesn't work quite that way but it doesn't matter. The "overhead" is called "phantom drain" and is part of your daily charging load at whatever rate you charge. It can be quite high if you use utilities like TeslaFi or Stats. As I do my phantom drain amounts to 4 kWh/da. Averaged over the 24 hrs in a day that's about 170W which is a good chunk of the 1440W provided by the 120V configuration of the UMC.

Full disclosure: I charge from solar. I am motivated to keep the total garage load (most of which is, of course, BEV charging) at or below solar cell production so that a little current as possible is drawn from the building's batteries. This minimized battery round trip current and prolongs their life.

I don't think I've ever seen a post so full of confidently incorrect assumptions in my life, and I've been online since the 90s. Impressive. Almost nothing in there is quite accurate. Close, and then you jump to a conclusion better than the best broad jumper.

 

[HaulingAss]

That's the thing. Most would be average. Or less. So no, most won't have a problem. You're not average. That's okay.

I think you are misrepresenting the meaning of the word "average" as actually used in this discussion.

When you say the "average" person drives 12,000 miles per year, that does not mean they drive 1,000 miles every month or 250 miles every week. For many years I was a commercial fisherman and I fit neatly into the "average" driving mileage of 12,000 miles per year although I didn't drive at all during the 4 months of the fishing season. Which means some months I drove a lot more than the average.

School teachers also tend to have seasonal driving patterns even if they fall into the 12,000 miles per year "average". But the real point here is that even people without seasonal work do not distribute their annual miles equally through the year. Which means we cannot rely on "averages" to say that 120V and 15 amps is enough for the "average" motorist, at least not for every week of the year. And, it's precisely those very busy weeks of a year that a motorist will feel extra pressure if they don't have enough time to charge. It's not a fun feeling. Of course the solution is simple, don't rely on a 120V plug for your home charging needs unless you are retired and a big day for you is a doctor's appointment. It's dumb.

That's not how EV charging rectifiers work. They're not PC power supplies. They have components that work at specific power levels. The units add together to make the requested power level. A 12a (for a 15a level 1 outlet) plus a 20a makes a 32a and so you have three levels from two circuits.

So it ends up the same efficiency. (Although often they are more efficient at 240 vs 120, but that's another thing entirely.)

-Crissa

I've explained this to you before and it's an established fact that you will use a lot less electricity if you charge near the top of the rated power for whatever charger your car has rather than from a regular 120v outlet and the reason why this is true has to do with the charging overhead that ajdelange mentioned in his previous post (his only good contribution).

To be specific, a car that takes 4 hours to charge 50% of the packs capacity at 48a 240 volts will take a whopping 32 hours to achieve the same thing through a standard 15 amp outlet (actually a bit longer due to the inefficiency of 120V charging).

So, ignoring the direct electrical inefficiency of 120V charging, the motorist charging at 120V will be charging 28 more hours to replace half of their battery capacity and there is overhead electrical consumption those entire 28 hours that the 48 amp charger only experiences for 4 hours.

I charge my electric mountain bike with 120 volts and it works great. A Cybertruck?

No, not in my worst nightmare. It's terribly inefficient.

 

[SwampNut]

I think you are misrepresenting the meaning of the word "average" as actually used in this discussion.

When you say the "average" person drives 12,000 miles per year, that does not mean they drive 1,000 miles every month or 250 miles every week. For many years I was a commercial fisherman and I fit neatly into the "average" driving mileage of 12,000 miles per year although I didn't drive at all during the 4 months of the fishing season. Which means some months I drove a lot more than the average.

School teachers also tend to have seasonal driving patterns even if they fall into the 12,000 miles per year "average". But the real point here is that even people without seasonal work do not distribute their annual miles equally through the year. Which means we cannot rely on "averages" to say that 120V and 15 amps is enough for the "average" motorist, at least not for every week of the year. And, it's precisely those very busy weeks of a year that a motorist will feel extra pressure if they don't have enough time to charge. It's not a fun feeling. Of course the solution is simple, don't rely on a 120V plug for your home charging needs unless you are retired and a big day for you is a doctor's appointment. It's dumb.



I've explained this to you before and it's an established fact that you will use a lot less electricity if you charge near the top of the rated power for whatever charger your car has rather than from a regular 120v outlet and the reason why this is true has to do with the charging overhead that ajdelange mentioned in his previous post (his only good contribution).

To be specific, a car that takes 4 hours to charge 50% of the packs capacity at 48a 240 volts will take a whopping 32 hours to achieve the same thing through a standard 15 amp outlet (actually a bit longer due to the inefficiency of 120V charging).

So, ignoring the direct electrical inefficiency of 120V charging, the motorist charging at 120V will be charging 28 more hours to replace half of their battery capacity and there is overhead electrical consumption those entire 28 hours that the 48 amp charger only experiences for 4 hours.

I charge my electric mountain bike with 120 volts and it works great. A Cybertruck?

No, not in my worst nightmare. It's terribly inefficient.

+1 to all that. It's math and not just opinions.

Everyone I know (anecdote, yes, duh) has different "average" and "peak" driving. I myself have basically zero normal days and only outlier days. My average miles are well below the national average, and yet a Leaf or Smart could not fit my "normal" days which are generally higher miles.

The cost and difficulty differential between a 30a outlet and a 50a is astronomical. That's why I've settled on that size and recommend it. I didn't build an opinion based on what I randomly chose; I carefully did the math to choose and to recommend (and help install). If you've ever worked with #6 wire versus #10, you know exactly what I'm saying.

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