# How does public-available charging of electric vehicles work?
**URL:** https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613
**Category:** Factual Questions
**Created:** [March 30, 2024, 7:19pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613 "2024-03-30T19:19:54Z")
**Posts on this page:** 20
**Page:** 2
### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 4, 2024, 11:58pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/21 "2024-04-04T23:58:33Z")
> [@dtilque](#):
>
> I think you mean kW and not A on those charge rates.
Doh!! Yes.
The Tesla superchargers I’ve had to frequent generally tended to be not far off the beaten track, i.e. just of the main highways on trips between cities. But then, for example, Ottawa - I had to drive halfway across the city to find the fast charger. The two free slow ones at the hotel were in use overnight. But then, they were in use by non0-Tesla EV’s so had my sympathy.
OTOH, how many hotels offer you a complimentary tank of gas with your stay?
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### Author:  [@Tripler](https://boards.straightdope.com/u/Tripler)
#### Post date: [April 6, 2024, 3:42pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/22 "2024-04-06T15:42:09Z")
Now that I’ve had a proper chance to recharge over coffee, and sink my teeth into this thread, I gotta thank you guys again, especially @echoreply and @md-2000 for the details.
> [@LSLGuy](#):
>
> The smart way to operate is fewer partial little charges with the battery level **kept in the 20%-90% full range**. Which is easy if you can plug it in at work or home.
> [@md-2000](#):
>
> Recommendation is as much as possible to **keep the battery between 20% and 80% or 90%**. So I have it set to automatically start charging at 1AM if plugged in - when I’m no longer using the dryer, hot water, oven, etc., AC demand is less, since the house only has 100A service. At 58k/hr (34mi/hr) I’ll be full by morning.
**Bolding by Tripler** both above an’ below. . .
This was something I wasn’t aware of. . . that I **will** keep in mind. One of the things that shocked me when I got into the first EV at Vegas was that the dash said the car was charged ‘only’ to 45%. I said to myself, “_Self, um, no. Not this one…_” and found another car (that happened to be an EV) on the Hertz lot. It too was down to %75 which seems to be SOP from what you guys said.
This seeming “lack ‘o’ juice” triggered the concern, 'beause as @LSL notes below (albeit not “laser-focused” but more “situationally-focused”) I need dependable transportation with known refueling options. . .
> [@LSLGuy](#):
>
> I was aiming my comment at @Tripler who seemed to be laser-focused on “drive it til it’s nearly empty.” Which may be appropriate for ICEs and **may be necessary in teh wide open western spaces he frequents**. Since he was talking about renting one on a trips and driving an EV for the first in an unfamiliar location, I thought it useful to recalibrate his ICE-centric unnoticed assumptions in very clear and simplified language.
The _last_ thing I need is to be stuck on a remote governmental site, with no access to roadside service, with the [greys](https://en.wikipedia.org/wiki/Grey_alien) hovering over me like vultures. (We’re not allowed to bring personal phasers on said sites–even if they are set on ‘stun’). There are no EV charging stations where I travel to (that I know of, it could’ve changed), but I wildly doubt it.
Tripler
All puns intended.
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### Author:  [@Spiderman](https://boards.straightdope.com/u/Spiderman)
#### Post date: [April 6, 2024, 5:09pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/23 "2024-04-06T17:09:53Z")
> [@Tripler](#):
>
> This was something I wasn’t aware of. . . that I **will** keep in mind. One of the things that shocked me when I got into the first EV at Vegas was that the dash said the car was charged ‘only’ to 45%. I said to myself, “_Self, um, no. Not this one…_” and found another car (that happened to be an EV) on the Hertz lot. It too was down to %75 which seems to be SOP from what you guys said.
For regular users that’s fine but if you’re going on a road trip, you’d want to start with 100% & would set your charger to give you a full charge the night before you left. EVs at an airport pickup probably shouldn’t follow the standard usage model because they have no clue where you’re going when you get there. Yes, a lot of people will just use it to drive around the city but there’s probably a decent percent of renters who are driving a distance from the airport & will now need to make a stop because they started off missing ¼ of their range.
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 6, 2024, 7:58pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/24 "2024-04-06T19:58:39Z")
> [@Tripler](#):
>
> when I got into the first EV at Vegas was that the dash said the car was charged ‘only’ to 45%. I said to myself, “_Self, um, no. Not this one…_” and found another car (that happened to be an EV) on the Hertz lot. It too was down to %75 which seems to be SOP from what you guys said.
My experience was the opposite. The Hertz site had the cars available plugged into slow chargers, and all were 100% or close to it. And their policy was to charge a “recharge fee” ($35 I think) not unlike the “bring it back full or else” for regular cars, or prepay it and bring it back however. The guy at the rental place said “for 100%, returning anything above 80% is fine”.
So you’re going to have to charge the car at least once, and there’s probably a charge on the way to where you’re going (and on the way back) so unless you’re in a real hurry, a 20-minute wait won’t hurt.
In an emergency, adding a few miles per hour with 110V may help get back to a charger if you are stuck somewhere overnight.
Hertz guy also said “verify it has the charging kit”, There could/should be a portable charger in the frunk, but ours didn’t have one - just the J1772 adapter. Important to make a note of this detail before you leave the site.
The portable charger takes a few ends - the one that came with our car (back in the days when it was included) had a NEMA 14-50 (like an oven) and standard household plug ends. Unless you find a a garage that has that NEMA 240V outlet - usually for tools like welders - you won’t use that, but it’s an option in an emergency.
I saw someone towed to the charger once, but they and the tow truck driver had no clue. Fortunately, they’d left the door open, the car was totally dead. Process was to climb through the back seat into the trunk to pull the latch (cloth ribbon cable) to insert the charger.
I never saw if they got to part B, but looked it up later for my own edification - the 12V battery was dead, it’s charged by the main battery, so the screen and all controls are dead. Apparently you have to pull the cover where the tow hook goes, exposing 2 wires that can be used (9V battery maybe, or 12V jumper) to trigger popping the power frunk open. Then remove the plastic cover by the windshield and jump the 12V battery with another vehicle. This will give the computer system the juice to eventually boot and start charging the main battery. Not sure how long before you can now disconnect the jumpers. (older cars have a regular battery, but newer versions have a small lithium block more dependent on the main battery.)
So strongly recommended NOT to get close to 0%. Also, there was a bit in the news about people in Chcago over winter who could not charge their cars. One of the features of the car is it will use power to warm the battery, and batteries will not charge below 0°C/32°F so if you don’t have enough juice to charge in winter, you need to find an indoor charger or you is up the creek. (Tow to a garage and let it warm, then do the boost trick). The “can’t charge” is evident driving in winter where for the first while the battery is cold and there’s no regen braking.
As I mentioned, check [plugshare.com](http://plugshare.com) for available chargers (one of the more detailed lists) and supercharge.info for Tesla charger locations. Both have zoomable maps.
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### Author:  [@DrDeth](https://boards.straightdope.com/u/DrDeth)
#### Post date: [April 6, 2024, 8:27pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/25 "2024-04-06T20:27:33Z")
> [@dtilque](#):
>
> The way to go is to plan the trip ahead of time in terms of which chargers you will use. And then only charge enough at any one stop to get you to the next charger. So a long trip turns into 2-3 hour drives punctutated by 20-25 minute breaks. One advantage is that you arrive much more refreshed than typically is the case with ICE vehicles, where you drive straight through for 8 or more hours, with only short 5 minute-ish breaks every 4 hours.
Plus enough power to get you a little further just in case, I assume.
I used to drive I5 from San Jose down to Santa Clarita every weekend (then back). Having old mans bladder, I found stopping at every rest sop broke up the drive, no “need to pee NOW” issues, and I arrived less stiff and more relaxed.
> [@md-2000](#):
>
> Home charging works out to about 1/10 the equivalent of gasoline (YMMV depending on kWh charges)
Everyone I know who has an EV or PHEV has home solar, so the charing is more or less free.
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 6, 2024, 8:50pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/26 "2024-04-06T20:50:29Z")
> [@DrDeth](#):
>
> Everyone I know who has an EV or PHEV has home solar, so the charing is more or less free.
I don’t have solar, but I estimate a “full tank” 500km/300mi is about $C7 or $US5.20 and it’s mainly hydro-electric power where I am. Not that I’d ever get to needing 0-100% charge in one go.
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### Author:  [@DrDeth](https://boards.straightdope.com/u/DrDeth)
#### Post date: [April 6, 2024, 8:53pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/27 "2024-04-06T20:53:05Z")
> [@md-2000](#):
>
> I don’t have solar, but I estimate a “full tank” 500km/300mi is about $C7 or $US5.20 and it’s mainly hydro-electric power where I am.
I am in sunny Socal, where AC is a need, not an option. In my neighborhood, most houses have solar.
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### Author:  [@hibernicus](https://boards.straightdope.com/u/hibernicus)
#### Post date: [April 6, 2024, 8:53pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/28 "2024-04-06T20:53:12Z")
A rental EV should be fully charged when you collect it. All this talk of managing the battery life by keeping the state of charge within certain limits is fine in theory, but if you rent a car you should expect it to be fully charged and to have the full range of the battery available to you.
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 6, 2024, 9:09pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/29 "2024-04-06T21:09:24Z")
Yes and no. The policy as I mentioned, was “return with about the same charge as you left”, so you will have to charge at least once, or end up paying a penalty about the same as a full tank of gas (in which case, where’s the savings?). Even a supercharger is only about half the cost of equivalent gas. If you are lucky, you stay at a hotel with a complimentary slow charger.
Let me also clarify - any lithium batteries will not charge if the battery is below freezing, (as I found with battery-wifi security cameras) and EV batteries are no different. Teslas use the battery power to heat the pack in preparation for charging; Supercharging works better with a warmer battery, so even in normal weather, the car will heat the battery an additional amount in preparation for supercharging if you indicate on your trip computer on the screen that you are headed for a charger. Otherwise, a cool battery (but above freezing) will charge slower until the charging heats it up, so indicating you are headed for a charger on your navigation screen is a good idea.
The battery will work at below zero to produce power if charged (as in, sitting outdoor at -20). Your range will appear limited until enough driving warms the battery.
But if you run the main battery down to zero, even at a charger, the 12V running the computer may not stay alive long enough to get the charging started and the battery charging. AFAIK the computer can tell the charger current to warm the battery instead, but the computer controls need to be running.
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### Author:  [@hajario](https://boards.straightdope.com/u/hajario)
#### Post date: [April 6, 2024, 10:48pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/30 "2024-04-06T22:48:55Z")
> [@DrDeth](#):
>
> Everyone I know who has an EV or PHEV has home solar, so the charing is more or less free.
That’s not how it necessarily works. I am looking into solar and the utility will only let you take 40% off of your bill. I am not sure how univeral that is but the sales reps told me that those day are over.
> [@DrDeth](#):
>
> I am in sunny Socal, where AC is a need, not an option. In my neighborhood, most houses have solar.
AC isn’t in need in Santa Barbara. Pretty much no one has it except maybe up in the foothills. All of the people with solar have EVs and/or a swimming pool that they like to keep warm.
* * *
I was told to try to keep the battery between 20% and 80% but it’s ok to top it off to 100% if you’re going on a longer trip. I’ll do that when I go to LA and back even though 80% will probably work. I don’t like probably.
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### Author:  [@hajario](https://boards.straightdope.com/u/hajario)
#### Post date: [April 6, 2024, 10:59pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/31 "2024-04-06T22:59:50Z")
Sorry for the double post but I used a supercharger on the day that I bought the car just to try it out. There were like eight cars parked and sixteen total spaces. I was expecting everyone to be hanging out being Tesla friends but all of the cars were empty. People must have been shopping. I was totally perplexed that there was nowhere to use my credit card. As mentioned upthread. I already had a credit card associated with the car and it just started juicing up and charging me.
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### Author:  [@dtilque](https://boards.straightdope.com/u/dtilque)
#### Post date: [April 7, 2024, 12:05am UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/32 "2024-04-07T00:05:07Z")
> [@hajario](#):
>
> I was totally perplexed that there was nowhere to use my credit card.
They don’t put credit card readers on the chargers because there’d be more breakdowns. The chargers are out in the open, so under more environmental stress than if they were indoors. To make the chargers more robust, they make them as simple as possible, which means not having things like credit card readers. Also note that the NACS plug is simpler than the CCS plug, which also makes them more robust.
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### Author:  [@DrDeth](https://boards.straightdope.com/u/DrDeth)
#### Post date: [April 7, 2024, 1:03am UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/33 "2024-04-07T01:03:02Z")
> [@hajario](#):
>
> AC isn’t in need in Santa Barbara.
Soon.
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### Author:  [@hajario](https://boards.straightdope.com/u/hajario)
#### Post date: [April 7, 2024, 2:24am UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/34 "2024-04-07T02:24:02Z")
🫠
Yesss
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 7, 2024, 3:45pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/35 "2024-04-07T15:45:14Z")
> [@hajario](#):
>
> I was told to try to keep the battery between 20% and 80% but it’s ok to top it off to 100% if you’re going on a longer trip. I’ll do that when I go to LA and back even though 80% will probably work. I don’t like probably.
It’s not an “OMG-toasted!” issue. The point is abusing the battery - running down to zero, up to 100%, over time will degrrade the battery faster. Supercharging too much is not as good as slow charging. OTOH, there was an article about a model S that had to have its battery replaced - after 180,000 miles of taxiing between LA and Vegas - which involved very hot weather, mostly supercharging several times a day. (Even then, an earlier model so less likely to have quality batteries - it got a replacement because one pack, some of the cells were failing) Unless you do something out of the ordinary for a lot of the time, your battery should be fine. the occasional 100% for a road trip, the occasional supercharging, even serial supercharging on a longer road trip, won’t hurt the battery.
One thing Teslas do is micromanage battery health, balancing charges between banks of batteries, monitoring temperatures, etc. There’s some videos of people doing 150mph on the Autobahn - the car will slow down when the battery gets too hot.
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### Author:  [@echoreply](https://boards.straightdope.com/u/echoreply)
#### Post date: [April 7, 2024, 6:14pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/36 "2024-04-07T18:14:26Z")
> [@md-2000](#):
>
> Supercharging too much is not as good as slow charging
This has long been the common wisdom, but this analysis suggests that it doesn’t matter. They found no statistical difference in battery health between cars that fast charge \>90% of the time and ones that fast charge \<10% of the time.
> **[Full Speed Ahead: EV Study Reveals Impacts of Fast Charging](https://www.recurrentauto.com/research/impacts-of-fast-charging)**
Looking at the headlines to other articles on that site, there are lots of things that will answer common EV questions, such as charging guides for new EV owners and discussions of terrain and temperature on range.
> **[Electric Vehicle Research & Insights | Recurrent](https://www.recurrentauto.com/research)**
>
> Follow the latest electric vehicle (EV) research and insights for buyers, drivers and dealers from used car leaders.
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 7, 2024, 6:25pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/37 "2024-04-07T18:25:47Z")
Anyway, after more than 5 years (Nov 2018) my battery still charges to 95% of nominal (379km vs. 400km). Another point is that there is no fill guage on a battery - the system tries to estimate the capacity from the charge level (voltage?) it detects. There’s a recommended procedure every so often (every 2 or 3 months) to calibrate the capacity estimation - charge fully leave unplugged an unused for 3 hours or more. Also at some time discharge to between 10% and 20% of capacity and let it sit for 3 hours before plugging in. This gives it a way to estimate high and low.
Anothe point I found with 100% charge from Hertz - when the battery is almost full, the car will not regen brake, it coasts like a gas car. It feels odd since I’m used to the car slowing when I ease off the accelerator.
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 8, 2024, 1:06am UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/38 "2024-04-08T01:06:36Z")
ALso need to point out this -
> **[Tesla offering LFP retrofits for Model 3 battery replacements under warranty](https://driveteslacanada.ca/news/tesla-offering-lfp-retrofits-for-model-3-battery-replacements-under-warranty/)**
>
> Tesla is now offering a lithium-iron-phosphate (LFP) pack retrofit to some Model 3 owners requiring a battery replacement under warranty. This option is now available for those vehicles that were initially equipped with the 2170 \[…\]
Apparently Tesla now ships most vehicles except performance with LPF batteries, where they say you can charge to 100% all the time with no drawbacks. Slightly heavier.
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### Author:  [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)
#### Post date: [April 8, 2024, 5:04am UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/39 "2024-04-08T05:04:08Z")
> [@Tripler](#):
>
> I’ve got a couple more business trips coming up soon, so I think I might give EVs a try!
Don’t! The current rental situation for EVs is horrible, which is why Hertz had to take a massive writeoff on their Tesla purchases a from a few years ago.
The value prop for EVs is that you should be doing 90+% of your charging at home, where the experience is many times better than a gas station, and \>10% of your charging at public chargers, where the experience is 10 - 3000% worse than a gas station. Renting a car means you’re by definition not at home.
The ideal use case for rental EVs is like, a business person who is in town for a couple of days and is just puttering around between different places in a city and puts less than 100 mi on the car before returning it. And the experience they should have is they are guaranteed to have a car at 100% charge when they get it and return it with whatever charge is left at no additional cost or at least a cost that is far cheaper than public chargers. But that would require much more serious investment by rental car companies to install robust charging infrastructure at their locations which they haven’t done yet.
> [@md-2000](#):
>
> And their policy was to charge a “recharge fee” ($35 I think) not unlike the “bring it back full or else” for regular cars, or prepay it and bring it back however. The guy at the rental place said “for 100%, returning anything above 80% is fine”.
This is such ICE brained thinking. The entire logic behind the charge for ICE cars is that it’s significantly more expensive for the rental company to send an employee off site to a gas station to fill up the car than you doing it yourself and it’s a tiny time commitment from drivers to top up the gas.
With EVs, it’s the exact opposite, you don’t need to send someone out, the charging happens on-site and the best time to charge the cars are overnight with off-peak electricity, inside a covered environment so you don’t have to build rugged, weatherized charging stations.
Hertz should have been encouraging every EV renter that the charging is better done at Hertz than anywhere else and they should just let Hertz take care of it. Instead, they went the exact opposite way and lost $250M and the CEO had to resign.
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### Author:  [@md-2000](https://boards.straightdope.com/u/md-2000)
#### Post date: [April 8, 2024, 12:50pm UTC](https://boards.straightdope.com/t/how-does-public-available-charging-of-electric-vehicles-work/999613/40 "2024-04-08T12:50:53Z")
The reason I rented Tesla (from Hertz) the last few times was because it was the same model, and software, I was already familiar with. My wife laughs every time I drive the BMW and forget and activate the windshield wipers when I mean to put the car in gear. You can rent an EV to try it out, but there’s a big difference between a car controls you’re familiar with and one that’s somewhat different. (Not just EV. The BMW went in for service and it took some searching afterward to find where to change the GPS screen to nightime mode automatically, something that accidentally got un-set)
But good points - the savings at a supercharger probably don’t mean much if you are travelling less than 100mi. Even if your hotel has a free overnight charger, EV’s are common enough it may be occupied nowadays (my experience). Save your experimenting for a free test drive at the Tesla store.
As I understood, the problem with Hertz is (a) high maintenance costs, Tesla parts etc. are still expensive and take a longer time to be delivered, and (b) they got hosed on the resale value as prices for new moels of the cars dropped. Plus, as you indicate, there’s no major advantage for a rental company on this type of car, considering they essentially do not themselves pay for fuel for regular cars.
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