How and why higher speed charging is more efficient

[ABCDE]

Hi guys. I’ve heard that charging faster is actually more efficient.
Would like to know the how and why if it. Second would like to know thoughts how much more efficient it is as I’m sure people have run some numbers and what this means for savings per month or year?? I read in someone’s post they said you would pay for the wall charger itself with the efficiency over a long time.
Sounds very appealing and would love to hear more info as that would make a good case for everyone to go wall charger if it pays for itself in efficiency. I was always under the impression the 120 was the way to go as it would be more efficient as in my mind there was less heat and this less losses??? Haha

 

[Uncle Paul]

While slow charging is more efficient than fast charging...240 Volt charging is much more efficient than 120 volt charging.

The higher voltage is more efficient than lower voltage, regardless of the speed of charge.

 

[Tam]

...less heat and this less losses??? Haha

Tesla uses HVAC to actively keep its battery in an optimal range of temperature so it can cool and heat your battery despite ambient temperature or heat from charging.

...120 was the way to go...

It's good for a small system but Tesla requires too much current for charging, HVAC and to step up from 120V to 400V...

 

[ZOMGVTEK]

The major issue has absolutely nothing to do with the efficiency of the charger or the input voltage. That has some non zero effect, but it’s not likely to be huge. The issue with charging at 120V 12A is how long it takes. This long duration means the car is ‘awake’ for a long time while it’s charging, and it consumes ~250W just to keep the car awake. So if it’s charging at 1400W this is nearly 18% losses right there. As the power goes up this isn’t as significant. It’s only ~2% at 11.5kW. Voltage I’m sure has some impact, but it’s most likely not that significant at 1.4kW.

The ‘savings’ from installing a wall charger to reduce the charge time and associated losses are not hugely significant fiscally. If the major goal is absolute savings it’s likely not going to pay off too quick even with expensive electricity, unless you charge a whole lot. But basically it means on the order of 15% higher charging cost. Assuming you drive 12,000 miles a yet at some vaguely reasonable efficacy, and have $0.25/kWh cost for electricity, it would save you maybe $150 a year. So 6-7 years under a basically ‘best case’ situation. That’s a lot of miles to recharge off a regular outlet, and quite high electric rates. For most people this would be likely beyond 10 years.

That said, I personally think it’s ridiculous to charge off a regular outlet. It’s suuuuppper slow and makes it so you need to actively consider the time it takes to recharge. For some people that drive short distances in mild climates it’s probably totally fine, but I wouldn’t recommend it as a general rule.

 

[ABCDE]

ZOM. I love you. Hahaha

wow. So thanks for explaining that in depth there man. I love it.

so for me in Hawaii. I think we’re at .33 cents a kWh?? So it would add up slowly over time which is kinda cool. Obviously as you state the lower the kWh the worse payback rate would be, or vice versa. So about 2 1/2 years for payback just based on your calculations.. then to factor in electrician which everything is higher here so payback is roughly 6 years on mine was because install.. so I mean if people do keep the car for ten years and have upfront cash and have a very good electrician rate. It’s not a bad idea to “diversify” your cash ( we are obviously just talking fun. I don’t think anyone buying Tesla’s are really counting pennies. Or I hope not ) just cool to say you get your money back what you put out down the road, with not ever have to hassle with range anxiety or stressing about timing. Pretty good deal if you ask me.

So very interesting. Didn’t know the car uses that much to stay on. Really appreciate everyone’s help here sharing as I know nothing about the car. I just drive it and plug it in.

jus think it’s something for people to think about. I guess all of us that have wall chargers that actually do keep them over time have it paid back in savings. Just great conversation material when someone’s poking in your garage and asks what the alien box is

 

[user212_nr]

jus think it’s something for people to think about. I guess all of us that have wall chargers that actually do keep them over time have it paid back in savings. Just great conversation material when someone’s poking in your garage and asks what the alien box is

You don't need to install a wall charger, as Tesla's included "mobile connector" can do 240v with some adapters.

I think what zoom means by "not significant fiscally" is that electricity is only a small part of your car ownership cost, not that you don't break even from installing the 240v outlet over time, if you paid $200 for that. If you paid $500 for the HPWC and $1000 for installation, as is common, then the math doesn't work out there.

 

[JenniferH]

ZOM. I love you. Hahaha

wow. So thanks for explaining that in depth there man. I love it.

so for me in Hawaii. I think we’re at .33 cents a kWh?? So it would add up slowly over time which is kinda cool. Obviously as you state the lower the kWh the worse payback rate would be, or vice versa. So about 2 1/2 years for payback just based on your calculations.. then to factor in electrician which everything is higher here so payback is roughly 6 years on mine was because install.. so I mean if people do keep the car for ten years and have upfront cash and have a very good electrician rate. It’s not a bad idea to “diversify” your cash ( we are obviously just talking fun. I don’t think anyone buying Tesla’s are really counting pennies. Or I hope not ) just cool to say you get your money back what you put out down the road, with not ever have to hassle with range anxiety or stressing about timing. Pretty good deal if you ask me.

So very interesting. Didn’t know the car uses that much to stay on. Really appreciate everyone’s help here sharing as I know nothing about the car. I just drive it and plug it in.

jus think it’s something for people to think about. I guess all of us that have wall chargers that actually do keep them over time have it paid back in savings. Just great conversation material when someone’s poking in your garage and asks what the alien box is

That alien box is my favorite part of my garage lol, especially glowing at night. Are you on Big Island by chance? That is where we live.

 

[SigNC]

while higher voltage is more efficient, that is true, the main win is the car is powered on less time and the ~300w it uses to be powered on is used for a smaller duration.

 

[Matsayz]

ABCDE,

One thing to think about is Tesla will hopefully keep the same type of charging head that you’re using right now for a long time so if you end up with another Tesla or a larger battery trim level then the HPWC might be a good buy. For most, as long as you’re 9-5pm M-F with less than 100miles a day... even the regular wall outlet 120V could do. It worked for me for 3months but damn am I happy with the 240V for $300 install.

 

[BEPA400]

The issue with charging at 120V 12A is how long it takes. This long duration means the car is ‘awake’ for a long time while it’s charging, and it consumes ~250W just to keep the car awake.

right so in my case where I run sentry mode 24/7 keeping it awake is moot and I drive low enough km that 120v 8amp seems to suffice for me.. every case is different.

It makes no sense to say ‘generally 120v makes no sense, or is bad’, rather stick with ’in xyz case with such and such criteria 120v makes no sense.’

 

[ZOMGVTEK]

right so in my case where I run sentry mode 24/7 keeping it awake is moot and I drive low enough km that 120v 8amp seems to suffice for me.. every case is different.

It makes no sense to say ‘generally 120v makes no sense, or is bad’, rather stick with ’in xyz case with such and such criteria 120v makes no sense.’

If it’s working for you that’s just fine. I said I don’t personally feel it’s a reasonable recommendation for most users. I don’t believe this dismisses it entirely. It sets them up for a high likelihood of a bad experience, and perpetuates the idea of long charge times for EV’s. This is making the assumption the individual that happens to be sufficiently intelligent to understand their needs can make a reasonable determination for their specific case. That leaves the ones that are not able to do this, and they very much need higher power charging than what a regular outlet with unknown voltage drop can provide. And then there’s the somewhat real risk of plugging an EV into a garage outlet that’s not normally run at full load for days straight. It’s probably OK, but it’s not something I feel comfortable recommending for the average person since the end result is very poor as well. It’s not terribly uncommon for outlets in older houses to be in a big loop with a dozen outlets on one circuit. Over the years some of these outlets get replaced by a homeowner with little electrical knowledge. This considerably increases the risk of issues the wall connector is going to be challenged to detect. In addition to this, in cold weather the car can barely get enough energy to charge and maintain a warm battery which pads the charge time quite appreciably. Trying to explain these factors to someone new to EV’s is almost sure to put them off, when all they really need to know is they should probably get a high power outlet in the garage and forget about it.

 

[toolman335]

There's no way I would have bought this car without a 240 wall charging station. I can't imagine using 120 and having to literally have it plugged in every second that I'm home. As time goes on I find myself thinking about my power less and less. I certainly don't wait for the E sign to come on like with my ICE, but I'm getting very comfortable. 120 would drive me insane.

 

[BEPA400]

Trying to explain these factors to someone new to EV’s is almost sure to put them off, when all they really need to know is they should probably get a high power outlet in the garage and forget about it.

That’s true it takes a lot to explain it even to other engineers at my office.. others I’ve explained to I’m pretty sure I could see my words going in one ear and out the other.. Fair point..

 

[ZOMGVTEK]

For whatever reason, the overwhelming majority of people are very thoroughly misinformed on EV’s. They know a few facts, and they’re all wrong. So making things simple and clear is probably a sensible approach. I’m not terribly concerned about the adaption of EV’s at this point. As far as I’m concerned it’s long since over, they won. But oddly enough the public is still not aware of this. They perceive Tesla’s as being 100K, slow to charge, short range, and potentially dangerous. I live in a cold climate, and it turns out lots of people think you can’t drive a Tesla in winter since they have computers, batteries, and the glass roof can break. One guy was trying to warm me that I can’t drive it in the rain since it’s dangerous. People are absurdly clueless, so it’s best to just say you need a dedicated charger installed and then it charges in ‘a few hours’. They usually understand that. And these are the people that go out of their way to inform me about EV’s. I’m surely not doing anything to solicit this insight, I can only imagine what the masses are convinced is true about EV’s.

 

[EVDRVN]

For whatever reason, the overwhelming majority of people are very thoroughly misinformed on EV’s. They know a few facts, and they’re all wrong. So making things simple and clear is probably a sensible approach. I’m not terribly concerned about the adaption of EV’s at this point. As far as I’m concerned it’s long since over, they won. But oddly enough the public is still not aware of this. They perceive Tesla’s as being 100K, slow to charge, short range, and potentially dangerous. I live in a cold climate, and it turns out lots of people think you can’t drive a Tesla in winter since they have computers, batteries, and the glass roof can break. One guy was trying to warm me that I can’t drive it in the rain since it’s dangerous. People are absurdly clueless, so it’s best to just say you need a dedicated charger installed and then it charges in ‘a few hours’. They usually understand that. And these are the people that go out of their way to inform me about EV’s. I’m surely not doing anything to solicit this insight, I can only imagine what the masses are convinced is true about EV’s.

I told a guy that my battery was developing a loss of range from the plaque coal fired electricity was pushing down the power lines. He said that was nonsense but did suggest the idea that the front wheels should have a generator to charge the battery as I drove so it would stay charged. I wish I had a dollar for every over unity / solar panel on the roof person that insisted it would work over the last 20 years.

 

[ZOMGVTEK]

I find it absolutely remarkable how common it is for people to both acknowledge they don’t know much about a topic, and yet suggest things that presumably would be obvious to those in the art, as some profound insight. People simultaneously say solar ‘doesn’t work’, and suggest someone puts panels on an EV so they never have to charge it. The average persons comprehension of energy is quite interesting.

 

[webbah]

Some of us that live in apartments don’t have chargers at all for the home. It’s not too inconvenient if you have public chargers nearby, but I’d love to even have the possibility at home.

 

[toolman335]

Right on guys with all of your talking points. Everyone has that brother in-law who prides himself on being an expert on every topic but knows nothing about anything. I get all of the same BS from him that was mentioned above.
Half of the people I work with can't believe I made it to work in the snowstorms this week(while they drive tiny front wheel drive Elantras and Sentras).
"Yeah, you're right guys. I don't know how my 4,000 lb AWD drive vehicle could drive on sloppy roads!"

 

[hugh_jassol]

Think of the 240V charging as a time-saver, not a money saver.