Odds of higher future 240V charge rates on the M3?

[Kirby64]

I think the Robo Taxi is being overlooked here. If a car is driving around all day, earning money, people would be willing to pay for faster AC charging, a car could be putting on 500 miles/day. Faster AC charing also allows a car to take more advantage of off-peak rates, which I suspect will be come more of a "thing" as intermittent renewables comprise a larger share of the grid.

I think the future use-case and energy pricing schemes will make faster AC charing more appealing and profitable.

If a car is traveling 500mi/day, it's not going to be charging itself for the majority of that on AC charging. That's where a supercharger is useful. Functionally, almost no car on a robotaxi network is likely to go 500mi/day. Average speeds are probably close to 30mph, so that means 500mi would have a car driving 16 hours a day... which is probably crazy optimistic.

In the scenario that your car is at home at night, there is no case where a full 8hrs won't recharge a Model 3 fully if charged at 48A.

The whole point of off-peak rates is to cut down power usage of AC which is highest between when folks get home and when they go to bed. Most plans I've seen are ~10PM->7AM or midnight-8AM for off-peak TOU. Even if the car returns with 0mi of charge, 7 hours of charging is sufficient to fully charge it on 48A.

 

[Evbwcaer]

If a car is traveling 500mi/day, it's not going to be charging itself for the majority of that on AC charging. That's where a supercharger is useful. Functionally, almost no car on a robotaxi network is likely to go 500mi/day. Average speeds are probably close to 30mph, so that means 500mi would have a car driving 16 hours a day... which is probably crazy optimistic.

In the scenario that your car is at home at night, there is no case where a full 8hrs won't recharge a Model 3 fully if charged at 48A.

The whole point of off-peak rates is to cut down power usage of AC which is highest between when folks get home and when they go to bed. Most plans I've seen are ~10PM->7AM or midnight-8AM for off-peak TOU. Even if the car returns with 0mi of charge, 7 hours of charging is sufficient to fully charge it on 48A.

Kirby, it seems like you think your generalizations apply to everyone and you think you've got it all figured out.

-To start, Superchargers cost more per/kwh than almost anywhere. So, if you are in the business of making money, and you can AC charge your car at home for 1/2 price, then that is attractive.

-Superchargers are not everywhere, they likely never will be everywhere, and they can be crowded.

-Many Robo taxis may go 500 miles per day. You probably are not imagining how Robo taxis might change car ownership and taxis service in general.

-No Tesla has a range of 500 miles, some have less than half that, throw in a buffer and winter and maybe we are looking at 180 miles. If those miles are not laid out perfectly, finishing at your destination at the 180th mile, then range is even less.

The whole point of AC charing is not only to discourage on-peak use, but promote off-peak use. Where I live, you can get off-peak just over 1 cent. Superchargers are around 20 cents. I am right, that any taxi service that could reduce their fuel costs 95% would have a huge competitive advantage and make more money as a result.

 

[Kirby64]

Kirby, it seems like you think your generalizations apply to everyone and you think you've got it all figured out.

-To start, Superchargers cost more per/kwh than almost anywhere. So, if you are in the business of making money, and you can AC charge your car at home for 1/2 price, then that is attractive.

-Superchargers are not everywhere, they likely never will be everywhere, and they can be crowded.

-Many Robo taxis may go 500 miles per day. You probably are not imagining how Robo taxis might change car ownership and taxis service in general.

-No Tesla has a range of 500 miles, some have less than half that, throw in a buffer and winter and maybe we are looking at 180 miles. If those miles are not laid out perfectly, finishing at your destination at the 180th mile, then range is even less.

The whole point of AC charing is not only to discourage on-peak use, but promote off-peak use. Where I live, you can get off-peak just over 1 cent. Superchargers are around 20 cents. I am right, that any taxi service that could reduce their fuel costs 95% would have a huge competitive advantage and make more money as a result.

It's a bit presumptuous to say I have everything figured out. I'm just pointing out that faster charging speeds don't actually do much to save you money in a robotaxi scenario.

Obviously superchargers cost more, but the whole point of taxi is that time is money. Time spent charging is time spent not earning money. If you actually think robotaxis that are trying to hit tons of utilization are going to charge off AC and only at night... then I think you're going to be mistaken. There's literally no way you can have both off-peak charging the entire time and run 500mi/day.

What's the actual scenario where a higher charging rate actually buys you something? Is the assumption that you can get extra rides by charging extra fast at the very beginning of off-peak then return before the completion of off-peak to charge more?

 

[SoundDaTrumpet]

I predict Tesla will not go above 48A charging rate as it requires a > 60A circuit. There something special about 48A.

Electrical code requires a local disconnect for anything larger than 60A. Jurisdictions have different opinion with what a local disconnect is. Some treat it like A/C units where it needs to be right there. Line of sight is generally require all-around. Local disconnect can be a breaker box, plug/receptacle, or a dedicated disconnect.

No such thing as a plug in type receptacles for greater than 60A.

Circuit breaker cost step jump up significantly beyond 60A.

It’s all about pleasing the masses electrically speaking.

 

[eprosenx]

I predict Tesla will not go above 48A charging rate as it requires a > 60A circuit. There something special about 48A.

Electrical code requires a local disconnect for anything larger than 60A. Jurisdictions have different opinion with what a local disconnect is. Some treat it like A/C units where it needs to be right there. Line of sight is generally require all-around. Local disconnect can be a breaker box, plug/receptacle, or a dedicated disconnect.

No such thing as a plug in type receptacles for greater than 60A.

Circuit breaker cost step jump up significantly beyond 60A.

It’s all about pleasing the masses electrically speaking.

Yeah, I generally agree that 48a is a pretty good sweet spot for a lot of folks/vehicles (and 32a for a lot as well).

I will call out that there is *no* requirement in the code for a "local disconnect" in the 2017 NEC. There just has to be a *locking* disconnect that is "readily accessible". Generally "readily accessible" does not require it within line of sight, but I think this is the main point of differing enforcement as it is not clearly defined in the NEC. I have posted the relevant code sections multiple times on the forum in the past (I don't have a link to all of it handy). Here is some of the code snippits: Model S - HPWC (High Power Wall Connector)

I do think that we will see the Tesla truck be higher than 48a. It will burn a ton more energy so it will need faster charging if they want to provide comparable charging speeds. My guess is that it will support 72a at a minimum. I could see them going all the way to 80a to max out what the Wall Connectors can provide (and 100a is a nice round number for a circuit size).

 

[Kirby64]

Yeah, I generally agree that 48a is a pretty good sweet spot for a lot of folks/vehicles (and 32a for a lot as well).

I will call out that there is *no* requirement in the code for a "local disconnect" in the 2017 NEC. There just has to be a *locking* disconnect that is "readily accessible". Generally "readily accessible" does not require it within line of sight, but I think this is the main point of differing enforcement as it is not clearly defined in the NEC. I have posted the relevant code sections multiple times on the forum in the past (I don't have a link to all of it handy). Here is some of the code snippits: Model S - HPWC (High Power Wall Connector)

I do think that we will see the Tesla truck be higher than 48a. It will burn a ton more energy so it will need faster charging if they want to provide comparable charging speeds. My guess is that it will support 72a at a minimum. I could see them going all the way to 80a to max out what the Wall Connectors can provide (and 100a is a nice round number for a circuit size).

So, does a 'locking disconnect' count if it's at the main feed line? Or does that mean you need a special breaker with a lock on your connection over to a HPWC?

Does putting a small piece of wire around the breaker to prevent you from resetting it without unscrewing it count as 'locking' ?

 

[Knightshade]

I think the Robo Taxi is being overlooked here. If a car is driving around all day, earning money, people would be willing to pay for faster AC charging

Why? DC is tons faster and if you're going with "TIME NOT ROBOTAXING IS MONEY LOST" then AC isn't the way to go regardless of if it's 10x slower than DC or only 5x slower.

 

[Knightshade]

-To start, Superchargers cost more per/kwh than almost anywhere. So, if you are in the business of making money, and you can AC charge your car at home for 1/2 price, then that is attractive.

If it still takes 5x the time? It's really not. That 5x time spent AC charging is time your robotaxi isn't making money on fares.

-Superchargers are not everywhere

Neither is my house with an AC charger. And there's far fewer "my house" than superchargers.

The whole point of AC charing is not only to discourage on-peak use, but promote off-peak use. Where I live, you can get off-peak just over 1 cent. Superchargers are around 20 cents. I am right, that any taxi service that could reduce their fuel costs 95% would have a huge competitive advantage and make more money as a result.

Wow I thought mine was cheap at just over 2 cents... where are you getting 1?

Still, let's check the math here... let's say you save 19 cents per kwh....and also magically ONLY need to refuel during off-peak power times... AND you magically have a 2x as fast AC charger available....

But that still means instead of charging 10% to 80% in 30 minutes at a supercharger stop you need to spend nearer 2.5 hours on AC.

That's a good 2 hours of fares you just lost out on to save...about 10 bucks in electricity costs.

Not so good business sense there buddy....

 

[Kirby64]

If it still takes 5x the time? It's really not. That 5x time spent AC charging is time your robotaxi isn't making money on fares.

Neither is my house with an AC charger. And there's far fewer "my house" than superchargers.

Wow I thought mine was cheap at just over 2 cents... where are you getting 1?

Still, let's check the math here... let's say you save 19 cents per kwh....and also magically ONLY need to refuel during off-peak power times... AND you magically have a 2x as fast AC charger available....

But that still means instead of charging 10% to 80% in 30 minutes at a supercharger stop you need to spend nearer 2.5 hours on AC.

That's a good 2 hours of fares you just lost out on to save...about 10 bucks in electricity costs.

Not so good business sense there buddy....

Nice math there. Either way you slice it, you're only losing out on fares potentially during off peak time though. So, how valuable are fares from say... 10pm-6am? 10 to ~3am is prime time on the weekends for most places, so you definitely don't want to be stuck charging on AC during that time. 5am onwards is probably valuable airport running times (for early flights)... So in the super-ideal full utilization scenario, I can see a tiny incremental benefit to charging super fast on AC between 3-5AM? Still, this all assumes the TOU charges are actually way way lower than regular pricing.

Here's the thing about TOU: If everyone suddenly owns an electric car (or just as higher adoption rate), then off-peak hours are suddenly going to become more heavily utilized and the incentive for low rates during the night goes down. The only reason power companies basically give away power during the nights is because it's too expensive to power down and power up continuous energy generation sources (e.g. coal, nuclear, whatever), so it's better to essentially give away that power. As the grid adapts, they don't need to actually discount it if they can just shuttle excess capacity into batteries or other storage devices... I'm not saying this happens over night (or, with today's policy climate... may not happen any time soon), but the reality is that super low rate TOU is an aberration. The power companies would prefer they had means of not just 'giving away' power.

 

[eprosenx]

So, does a 'locking disconnect' count if it's at the main feed line? Or does that mean you need a special breaker with a lock on your connection over to a HPWC?

Does putting a small piece of wire around the breaker to prevent you from resetting it without unscrewing it count as 'locking' ?

You need to be able to place the single circuit feeding the wall connector in the “off” state in a “locked” fashion. Basically so that nobody comes along and resets it while you are working on it.

UL approved locking devices are generally available that basically do precisely what you describe. They just cover the breaker and let you “lock” it in the off position.

They would not let you use a lock on the main disconnect for this since that would shut off other things and hence discourage it’s use.

 

[Kirby64]

You need to be able to place the single circuit feeding the wall connector in the “off” state in a “locked” fashion. Basically so that nobody comes along and resets it while you are working on it.

UL approved locking devices are generally available that basically do precisely what you describe. They just cover the breaker and let you “lock” it in the off position.

They would not let you use a lock on the main disconnect for this since that would shut off other things and hence discourage it’s use.

So what I'm hearing is that when the inspector comes by I can tell him my piece of wire and a pair of pliers is my 'locking disconnect' and it should be fine

Or I guess I can just buy the pesky breakers that include a ring to actually lock it with...

 

[eprosenx]

So what I'm hearing is that when the inspector comes by I can tell him my piece of wire and a pair of pliers is my 'locking disconnect' and it should be fine

Sure! As long as you can get it UL listed. ;-)

 

[wws]

One thing that hasn't been mentioned in this thread yet is "real estate". In the Model 3 the charging module resides inside the battery pack. I'd imagine there isn't much additional space that they could allocate to a higher power charger option.