Why do I need a wall charger at all?

[STS-134]

120V home charging sucks, 32 Amp charging sucks less, 48Amp charging can still suck at times but its the best we got at the moment.

There's nothing in theory that would prevent a homeowner from installing 3ϕ electricity and then installing a DC fast charger in his or her garage. Just would require enough money and the proper permits. I tried to get a quote for 3ϕ service when I was doing my service upgrade (not for DC fast charging and not because I really needed it but because I was just curious about what it would cost) and was given a ballpark amount of "somewhere in the 6 figures". I ended up going with 400A peak/320A continuous split phase service which I could do for a cost in the very low 5 figures.

Of course, assuming I had a DC fast charger in my garage I would have used it probably exactly once (for testing) and actually needed it zero times. Not sure if I'd ever actually use it due to concerns about battery life. Plus, a single use during any given month would probably subject me to ridiculous demand charges as well.

Stand-alone 14-50 outlets and mobile connectors don't support load balancing, so if you decide to add another outlet at a later date, you might have to add a subpanel or run another line from a different breaker. Depending on the size of you panel/subpanel, you might have to manually ensure both weren't charging at the same time.

I don't think you are allowed to put more continuous load on a panel or subpanel than 80% of its capacity. So 3 separate 48A EVSEs wouldn't be allowed even on a 150A panel. Since EVSEs are all continuous loads, they eat into your amperage budget much more than things like stoves, ovens, and dryers.

 

[MorrisonHiker]

I don't think you are allowed to put more continuous load on a panel or subpanel than 80% of its capacity. So 3 separate 48A EVSEs wouldn't be allowed even on a 150A panel. Since EVSEs are all continuous loads, they eat into your amperage budget much more than things like stoves, ovens, and dryers.

We have a subpanel to our garage and then another subpanel just for the wall connectors. Each of the wall connectors has breakers that allow them to charge at up to 80 amps since we have gen 2 wall connectors. The load balancing feature limits the three wall connectors (EVSE) to 80 amps total. Only 100 amps total goes to the sub-subpanel but each has its own 100 amp breaker and each could charge at 80 amps. Newer gen 3 wall connectors are limited to 48 amps each (instead of 80). With gen 3 wall connectors, they support even more load balanced connectors. Anyhow, my post above was just to point out another benefit of wall connectors vs. a mobile connector: load balancing.

 

[STS-134]

We have a subpanel to our garage and then another subpanel just for the wall connectors. Each of the wall connectors has breakers that allow them to charge at up to 80 amps since we have gen 2 wall connectors. The load balancing feature limits the three wall connectors (EVSE) to 80 amps total. Only 100 amps total goes to the sub-subpanel but each has its own 100 amp breaker and each could charge at 80 amps. Newer gen 3 wall connectors are limited to 48 amps each (instead of 80). With gen 3 wall connectors, they support even more load balanced connectors. Anyhow, my post above was just to point out another benefit of wall connectors vs. a mobile connector: load balancing.

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Yes but my point is that you're not allowed to just connect stuff and then "manually ensure both weren't charging at the same time" like you suggested. You're not allowed to connect so much equipment to a panel that it would overdraw if everything was being used simultaneously AT ALL. 2 EVSEs not doing load sharing, both configured for 48A on 60A breakers, on a 100A panel is just not allowed, period.

 

[MorrisonHiker]

Yes but my point is that you're not allowed to just connect stuff and then "manually ensure both weren't charging at the same time" like you suggested. You're not allowed to connect so much equipment to a panel that it would overdraw if everything was being used simultaneously AT ALL. 2 EVSEs not doing load sharing, both configured for 48A on 60A breakers, on a 100A panel is just not allowed, period.

Ah yes, sorry, I probably worded that incorrectly. Before we had our wall connectors, we had two 14-50 outlets. They only used 80 amps max when both were in use.

 

[bradtem]

I charged with a NEMA 5-15 for about 6 months, "upgraded" to charging with the 5-20 which made a big difference. Then went to a 14-50 at 40 Amps with the older mobile charger. Still none of those compare to the 48Amps you can get from the wall connector. There were many times when I used the 120V where I would have to go to the supercharger before going home because the 1-2%/hour gain from the 120V would not cut it for my plans for the next day. Even after upgrading to the 14-50, there were times I wish it charged quicker because my plans changed and I needed more energy for afternoon plans.
Long story short, we all are going to have our "subjective" opinions on which charger fits best. Buy whatever you can afford. Overall the ownership experience will be improved with faster home charging. 120V home charging sucks, 32 Amp charging sucks less, 48Amp charging can still suck at times but its the best we got at the moment.

There are people who have driving plans that need more, but the average person does not. You have to figure out what your driving plan will need,and decide if it's worth the money to put in more charging. If it's not much money, then go for it. If it's a lot of money, dig deeper. There are people who don't have home charging at all though I do not recommend this. Level 1 will require occasional supercharger visits, but not many for most people. For people with a long regular commute it can be an issue.

The bigger your battery, the less you need faster charging, which is something that goes against many people's intuitions. They read some stat like "It would take 50 hours at level 1 to recharge fully" but you never recharge fully and very rarely need to go all the way even to 80%. Going to 60% on some days is fine unless you plan a big driving day the next day. (Then you supercharge.)

That is not as convenient as having 7kw at home, but if getting the 7kw is costly, you want to consider it. The average car drives 12,000 miles per year, which is 33/day, which is more than replenished overnight at Level 1. Of course some days are heavy driving and some none, and when you do 3 heavy days in a row, you can start getting low. But it generally works.

 

[LoL-Gas]

There are people who have driving plans that need more, but the average person does not. You have to figure out what your driving plan will need,and decide if it's worth the money to put in more charging. If it's not much money, then go for it. If it's a lot of money, dig deeper. There are people who don't have home charging at all though I do not recommend this. Level 1 will require occasional supercharger visits, but not many for most people. For people with a long regular commute it can be an issue.

The bigger your battery, the less you need faster charging, which is something that goes against many people's intuitions. They read some stat like "It would take 50 hours at level 1 to recharge fully" but you never recharge fully and very rarely need to go all the way even to 80%. Going to 60% on some days is fine unless you plan a big driving day the next day. (Then you supercharge.)

That is not as convenient as having 7kw at home, but if getting the 7kw is costly, you want to consider it. The average car drives 12,000 miles per year, which is 33/day, which is more than replenished overnight at Level 1. Of course some days are heavy driving and some none, and when you do 3 heavy days in a row, you can start getting low. But it generally works.

I disagree with the bigger battery needs less charging. The bigger the battery the greater the need for faster home charging. The hummer EV perfectly illustrates this, but I'll keep the discussion to Teslas. The bigger the battery, the more energy the vehicle is using per mile traveled. Charging on Level 1 would net you ~8-12kWh over 8-12 hours of charging (overnight). Let's say you average somewhere between 300-400wh/mile (350wh/mile): This would only add 23-34 miles of RATED range overnight. On average the car gets about 70% efficiency: driving 33 miles uses 47 miles of RATED range. M-F of driving to work and then charging up in the garage would lead to a net negative each and every day. Factor in cold weather, snow, rain, heat, family things (these are four door sedans and SUVs), etc... it just exacerbates the situation. You may be able to squeak by through the week, planning on letting the car charge 24/7 over the weekend. And then supplement with supercharging to bump you up during an emergency.

Also the average mileage driven per year has gone up. 12,000 miles is probably from sometime in the 1990s. Its closer to 15,000 nowadays.

Toss in a wall connector, charge the car up in a hour (12kW per hour). Situations to highlight: Opps I had to drive 200 miles today for something unplanned, arrive home at 0%, car charges to 90% overnight. My city charges more during peak hours, I can optimize pricing by charging between 11pm and 6am, the wall connector can fill the car up during that amount of time.

 

[bradtem]

I disagree with the bigger battery needs less charging. The bigger the battery the greater the need for faster home charging. The hummer EV perfectly illustrates this, but I'll keep the discussion to Teslas. The bigger the battery, the more energy the vehicle is using per mile traveled. Charging on Level 1 would net you ~8-12kWh over 8-12 hours of charging (overnight). Let's say you average somewhere between 300-400wh/mile (350wh/mile): This would only add 23-34 miles of RATED range overnight. On average the car gets about 70% efficiency: driving 33 miles uses 47 miles of RATED range. M-F of driving to work and then charging up in the garage would lead to a net negative each and every day. Factor in cold weather, snow, rain, heat, family things (these are four door sedans and SUVs), etc... it just exacerbates the situation. You may be able to squeak by through the week, planning on letting the car charge 24/7 over the weekend. And then supplement with supercharging to bump you up during an emergency.

Also the average mileage driven per year has gone up. 12,000 miles is probably from sometime in the 1990s. Its closer to 15,000 nowadays.

Toss in a wall connector, charge the car up in a hour (12kW per hour). Situations to highlight: Opps I had to drive 200 miles today for something unplanned, arrive home at 0%, car charges to 90% overnight. My city charges more during peak hours, I can optimize pricing by charging between 11pm and 6am, the wall connector can fill the car up during that amount of time.

You have hit on the important point, but it's not the size of the battery, it's the efficiency of the car. A long range model 3 and a standard range are very similar in efficiency. The long range needs less home charging, because it can tolerate wider swings in daily SoC, and will eventually get back up to full as long as your average miles are normal. A short range car like and 90 mile leaf needs much faster charging than a Tesla long range, because you must fill the Leaf fully each night. No good to just add 50 miles to it, the way it is with my model 3.

 

[STS-134]

You have hit on the important point, but it's not the size of the battery, it's the efficiency of the car. A long range model 3 and a standard range are very similar in efficiency. The long range needs less home charging, because it can tolerate wider swings in daily SoC, and will eventually get back up to full as long as your average miles are normal. A short range car like and 90 mile leaf needs much faster charging than a Tesla long range, because you must fill the Leaf fully each night. No good to just add 50 miles to it, the way it is with my model 3.

Constantly charging your battery to 90% just because you might need to use it and it takes 3 days to charge up to that point otherwise isn't good for your battery health though. I'm happy with my 240V/48A charging because I can keep my battery at 50% for daily use and if I ever need to go higher, it doesn't take very long to get there.

 

[LoL-Gas]

Constantly charging your battery to 90% just because you might need to use it and it takes 3 days to charge up to that point otherwise isn't good for your battery health though. I'm happy with my 240V/48A charging because I can keep my battery at 50% for daily use and if I ever need to go higher, it doesn't take very long to get there.

That's what I do, keep it low and quickly 'fill up' if I need it. A great benefit of the wall connector. Even better if I could get a 50kW DC charger in the garage but I don't want to spend that much.

 

[strider]

You've been bragging that you can unplug your mobile connector and use that outlet for other things so you obviously don't keep the mobile connector plugged in at all times. And on top of that, a crappy $10 NEMA 14 outlet was not designed to have stuff unplugged and plugged into it constantly over its lifetime, unlike a 5-15 outlet. This stuff typically gets used for stuff like stoves and ovens and dryers and other permanently installed appliances that gets plugged in when the appliance is installed and unplugged when the appliance is replaced. So expectation when it was manufactured was maybe 3-5 cycles (devices plugged into it and unplugged from it) before the outlet is replaced. Hell, I have had a NEMA 10-30 outlet melt and destroy a dryer plug and dryers don't even put the same type of load on an outlet that EVSEs do.

Not sure if that is directed at me, but I do not think "bragging" is appropriate. I remove my mobile connector once or twice per year. As I have stated, I have been using Tesla mobile chargers for 12 YEARS. You (checks account creation date....) have been here 14 months yet you speak as if you have some kind of authority and expertise when it comes to charging Teslas.

The whole reason that code requires a 20% derate for continuous loads is precisely due to heating. Improper installation will cause hotspots whether that it a 14-50 or a wall connector. There is nothing inherently safer with a wall connector than a mobile connector assuming both are installed and used correctly. The mobile connector has a temp sensor in it just like the wall connector. Plus if things get too hot then the breaker will trip. that is its job.

You are correct that the Gen 1 Model S mobile chargers did have problems. But the problems were where the (Tesla) plug adapter plugged into the (Tesla) EVSE when run at 40A. The problems were not at the plug (unless there was substandard installation). One of the 4 threads that @father_of_6 linked above was from a wall charger. Again, I never suggested that anyone "cheap out" on their charging install. But it is a fact that a properly installed 14-50 is just as safe as a properly installed wall connector. You trying to scare people into doing things "your way" is petty and sad.

You may be surprised to learn that RV parks have 14-50s and they are plugged and unplugged hundreds of times per year, year after year. Please point me to the rash of fires resulting from this. I'll wait.....

 

[LoL-Gas]

You have hit on the important point, but it's not the size of the battery, it's the efficiency of the car. A long range model 3 and a standard range are very similar in efficiency. The long range needs less home charging, because it can tolerate wider swings in daily SoC, and will eventually get back up to full as long as your average miles are normal. A short range car like and 90 mile leaf needs much faster charging than a Tesla long range, because you must fill the Leaf fully each night. No good to just add 50 miles to it, the way it is with my model 3.

You lost me at the Leaf comment. I think you are mixing ideas up a little bit...And the size of the battery means more weight and usually less efficient of a vehicle DUE to the heavier battery pack. You gave two similar cars, battery packs in the same neighborhood. Compare a 60kWh pack to a 100kWh pack and let me know what you get. Or compare a 20kW pack (like the leaf you describe) to the 60kW pack. The only reason I bring up the battery pack size is due to weight and decreasing efficiency. Wether it is from the pack or from the car it is put in. Larger packs are usually in less efficient cars (small exceptions).
TLDR: 120V charging, while okay, leads to a less than optimal ownership experience. Heck, even 240V32A is less than ideal.

 

[LoL-Gas]

The whole reason that code requires a 20% derate for continuous loads is precisely due to heating. Improper installation will cause hotspots whether that it a 14-50 or a wall connector. There is nothing inherently safer with a wall connector than a mobile connector assuming both are installed and used correctly. The mobile connector has a temp sensor in it just like the wall connector. Plus if things get too hot then the breaker will trip. that is its job.

Circuit breakers 'trip' from heat?

 

[bradtem]

You lost me at the Leaf comment. I think you are mixing ideas up a little bit...And the size of the battery means more weight and usually less efficient of a vehicle DUE to the heavier battery pack. You gave two similar cars, battery packs in the same neighborhood. Compare a 60kWh pack to a 100kWh pack and let me know what you get. Or compare a 20kW pack (like the leaf you describe) to the 60kW pack. The only reason I bring up the battery pack size is due to weight and decreasing efficiency. Wether it is from the pack or from the car it is put in. Larger packs are usually in less efficient cars (small exceptions).
TLDR: 120V charging, while okay, leads to a less than optimal ownership experience. Heck, even 240V32A is less than ideal.

I did tell you. The long range is only slightly less efficient due to the extra weight. Not enough to alter this equation. I described the same car with small and large pack. What matters is wh/mile, not vehicle type or pack size. They affect the wh/mile, and I am repeating:. With two cars of roughly similar efficiency, the one with larger battery can get by with slower charging. The mistake of thinking the reverse is quite common of course, particularly before people get an ev and slower home charging

 

[STS-134]

Not sure if that is directed at me

It wasn't. It was directed at the post immediately prior to that one. I couldn't quote it directly because that member accidentally put his reply text into the quote box itself.

The whole reason that code requires a 20% derate for continuous loads is precisely due to heating. Improper installation will cause hotspots whether that it a 14-50 or a wall connector. There is nothing inherently safer with a wall connector than a mobile connector assuming both are installed and used correctly. The mobile connector has a temp sensor in it just like the wall connector.

That's true in the case of the mobile connector, but only because it has a temp sensor in the plug itself. Whatever else you could plug into that 14-50 (including a Gen 1 Mobile Connector) may not have a temp sensor in it.

Plus if things get too hot then the breaker will trip. that is its job.

The breaker will only trip from heat if its thermal trip mechanism gets too hot. If the wire that attaches to the breaker has a bad connection at the spot where it attaches to the breaker and it heats up, it's possible for the breaker to sense the heat and trip. If the plug and outlet are getting hot, there's no way the breaker will sense that.

You may be surprised to learn that RV parks have 14-50s and they are plugged and unplugged hundreds of times per year, year after year. Please point me to the rash of fires resulting from this. I'll wait.....

The problem isn't with 14-50 outlets in general. It's with cheap 14-50 outlets like Leviton outlets, especially ones with weak and half length contacts. RV parks probably use something better than a $10 Leviton piece of junk. If you use a quality outlet like a Hubbell or Bryant, you're fine. I have both a WC and a 14-50 outlet and when I replaced the Leviton receptacle with the Hubbell, one of the first things I noticed was how much cooler the plug stays when I charge the car. The big difference is that the Hubbell has full length contacts. When the low quality half length contacts on the cheap Leviton outlets stop gripping the prongs as they should, the plug often overheats and it destroys both the receptacle and the plug.

Circuit breakers 'trip' from heat?

They can. They contain a thermal trip mechanism and if it gets too hot, the breaker will trip. But this will only happen if too much current is flowing through the breaker or if the wire attached to the breaker screw heats up at that spot. It won't happen if something far from the breaker box is getting too hot.

 

[LoL-Gas]

I did tell you. The long range is only slightly less efficient due to the extra weight. Not enough to alter this equation. I described the same car with small and large pack. What matters is wh/mile, not vehicle type or pack size. They affect the wh/mile, and I am repeating:. With two cars of roughly similar efficiency, the one with larger battery can get by with slower charging. The mistake of thinking the reverse is quite common of course, particularly before people get an ev and slower home charging

So if you took that same model 3, and put in that leaf battery that has 90 miles of range, it wouldn't do as well with 120V charging? Im confused......

 

[bradtem]

So if you took that same model 3, and put in that leaf battery that has 90 miles of range, it wouldn't do as well with 120V charging? Im confused......

Yes. How could you put the leaf battery in a model 3, that makes no sense.

Just compare a LR model 3 and an SR, the LR is only a little less efficient. And can get by with slower charging because it can range up and down more.

 

[LoL-Gas]

Yes. How could you put the leaf battery in a model 3, that makes no sense.

Just compare a LR model 3 and an SR, the LR is only a little less efficient. And can get by with slower charging because it can range up and down more.

Not the actual battery, the kWh size pack from the leaf to the model 3....

 

[bradtem]

Not the actual battery, the kWh size pack from the leaf to the model 3....

Right, but what I am saying is the important thing is to look at the efficiency and size of pack. One way to understand this is to view the pack size and change rate in miles. If you average 35 miles/day you need a charger that can restore that much per day. Level 1 can do 50 miles in a typical 10 hour overnight, 40 miles in an 8 hour overnight. Which is enough. The bigger the pack, the more acceptable it is. If you had a 1,000 mile pack (like the Aptera wants to claim) then you could get by with slightly less, because as you wander up and down, the odds you get to zero are much less. If you have a 100 mile pack like the Leaf, the chances you will get to zero as you wander up and down are vastly greater, so you need faster charging for that smaller pack.

With a 250 mile pack, one day you might drive 60 miles and restore only 40. So now you are down 20. Do it again you are down 40. Do it 10 times and you are down to 50 miles and you can't do the 11th day. In a 100 mile pack you can only do it one day before you are too low. You must be able to charge faster. In reality, you are very unlikely to try to drive 60 miles every day for 11 days -- not if your average is 35 miles. It can happen but it's very rare. So you fast charge if it does. With the 100 mile pack you will be in trouble a lot, it doesn't really work. You need a faster charger that can give you 80 miles in a night.

 

[Earl]

Not the actual battery, the kWh size pack from the leaf to the model 3....

I think you're getting caught up in the ICE paradigm where vehicle mass has a very big affect of vehicle efficiency.
While mass does affect the efficiency an EV, it does not have as big an effect as it does with an ICE. With the ICE, mass impacts the fuel used for acceleration as well as the tire drag while driving. Regenerative braking captures a lot of the excess energy that an EV loses while accelerating and the flat power curve of an EV mean it is operating at high efficiency throughout all speeds as it accelerates. An ICE, even with the massive number of gears they're putting in today, still is not at peak efficiency except when the gear puts it into its narrow efficient band.
The reason big vehicles like the Hummer and F-150 use so much more energy than Teslas is because of their aerodynamic drag which is proportional to their coefficient of drag (smooth shape) and frontal area (overall size).