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Comment by stcredzero | Hacker News Reader

I used to run an extension cord out of my 2nd floor window, but I wasn't parking on the street. My space was off the driveway, behind a fence and a gate, but only about 12 feet from the curb.

More recently, I had been parking an electric car in my apartment's lot, and running an extension cord from the exercise room, out to the car. Then the apartment decided to close off those outlets.

In both cases, the car's battery was only 24Kwh. With 110 volts, it took about 18 hours to fully charge. With a battery the size of a Tesla, that charging rate is going to take all week.

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I used 120v exclusively for the first 3 months I owned my Model 3. It took a few days to get back full after a long trip but it worked great for day to day driving.

I did finally put in 240v but only because it was easy since I just had to go through 1 concrete wall. This does speed it up 5x the 120v rate (2x volts @ 2.5x amps) which is nice after you drop down to a low charge but not really noticed in day to day use.

I think "charging time" is the wrong metric to think about. The relevant metric is "miles/h". The model 3 may have a giant battery pack that takes forever to charge fully, but it's also very efficient so whatever electricity you get into it corresponds to more miles. All that matters for the situation to be sustainable is that you drive less than the amount of miles that you can charge while not driving, on average. That's a simple comparison between miles driven, the current you can charge at, and the number of hours you can charge per day.

The average car is only driven enough miles per day to require about one night of charging at 120V to top off. A lot of folks, even Tesla owners, get by fine just using existing 120V sockets.

I get by with a 100' extension cord (12 gauge) for my 100D Model S charging off 120V. The vehicle detects the voltage drop and reduces its charge rate accordingly. 36-48 miles of range per 12 hours added to the vehicle (the average American round trip commute is ~34 miles/day).

If I'm in a pinch, I'll pop over to a Supercharger for a top up, which is at the local grocery store so I'm shopping anyway. The charge is so fast (~150kw charge current, ~25 minutes), I sometimes have to go move the car mid shopping trip.

There's a guy with a Tesla around the corner from me, who does this (cable out the 2nd floor window), and he does park on the street. Not sure what he does if he can't get a space close enough. (A neighborhood of row houses with little off-street parking)

I think the car makers have to accelerate integrating solar charging into their cars. You probably wouldn't get 100% of your charge that way, but you could get enough to substantially reduce dependence on the grid.

Leaf had a solar charger as a gimmick. It doesn't work. There isn't enough panel space.

The Leaf solar charger is for the 12 volt system, which is separate from the main battery. I can't really conclude if it is a gimmick or not but my 12 volt battery has not yet died. To be fair, the car also charges the 12 volt battery when it is plugged in.

I wonder what pedestrians et al. think about the cable running across the sidewalk. I don't think this solution scales well, also from an insurance perspective.

There was a time when I was renting a room in a house in East Oakland. The home owners had a traffic cone, and I used one of those cable-covers to cross the sidewalk. I never had a problem, other than overhearing a young woman who lived next door call me, "That douchebag with the electric car."

My neighbor does this as well. He does cover the cable with a piece of vinyl. I see him dicking around with his extension cord and vinyl several times a week, and then he tells me how charging EVs is totally not a problem and how convenient his car is. In the mean time I spend 5 mins every 3-4 weeks to fill my car up with diesel and I'm good for another 8-900 km. I wouldn't want an electric car today if I got one for free (well then I'd probably take it, I'm Dutch after all)

Someone in my old neighborhood did this too. It generally seemed like a pretty bad idea, but it didn't actually bother me.

Not substantially, no.

> I think the car makers have to accelerate integrating solar charging into their cars.

Nah. Solar on cars is a dead-end -- even with perfectly efficient solar panels, a clear sky, and the sun at the zenith, the most power you can possibly get is 1.3 kW/m² (cf. [1]). I don't know exactly how large of a solar panel you could put on a car, but even with a huge 5 m² panel, you'd still be looking at over 12 hours (i.e, multiple days of charging) to charge a Tesla's 85 kWh battery. With realistic panel efficiency and sun conditions, it'd take even longer.

[1]: https://en.wikipedia.org/wiki/Solar_constant

> over 12 hours (i.e, multiple days of charging) to charge a Tesla's 85 kWh battery.

The tone is somewhat pessimistic.

Full charge every two-to-three days for a range of ... what is it? 265 miles? Effectively untethered car if you only need 50 miles daily.

Again, keep in mind my numbers are assuming a large, perfectly efficient solar panel under ideal conditions. Realistic numbers will be much worse. For example, most commercially available solar panels are 20-25% efficient.

1.3kW/m^2 * 20% efficiency = 260w/m^2

260w/m^2 * 5m^2 = 1.3kW

1.3kW * 4 hours daily sun = 5.2kW/day

265 miles range / 85kW full charge capacity = 3.1 miles/kW

5.2kW/day * 3.1 miles/kW = 16.12 miles / day

Still sounds too good, what did I miss?

That initial 1.3kW is ignoring atmospheric absorption. You lose some 300 W even at zenith without clouds. More if you're really far from the equator and/or it isn't currently solar noon. If you're in a city, you may be in shade a lot and certainly don't have the sun at its zenith for 4 hours regardless.

5m^2 is too big for a car, and the panels are heavy and expensive. Toyota used to have a prius with a solar panel roof - it produced enough energy to run the fans (not the AC) while the car was parked on a hot day. Not even in the ballpark of the energy needed to move the car (and it was an expensive option).

16.12 miles a day is not going to cut it. In your previous comment you suggested 50 miles a day. In various studies, Americans drive >30 miles a day.

16 miles would hardly even cover most American's one-way commute, let alone any other errands or trips.

>you suggested 50 miles a day

/s/suggested/calculated using data provided by parent comment/

Nobody in the entire comment chain brought up distance except for you, which you kicked off by suggesting 50 miles daily usage.

Regardless, even your drastically lower 16 miles a day isn't going to satisfy the needs of the average driver.

Affordable solar panels don't get 260W/m^2 peak. The solar panels on a car don't track the sun, so average power output is way below peak.

You don't get 1.3kW per square meter for 4 hours a day. 42,339 MW of PV installations produced 39,401 GWh of energy in 2017 in Germany[1], so on average you get peak power for just two hours a day with panels that are angled appropriately.

[1] https://en.wikipedia.org/wiki/Solar_power_in_Germany#Statist...

Then you get not all of you charge from the solar panel, but a quarter to a half. So what? That's still good. If the car basically had 20 free miles a day, that would mean much less reliance on plugging in.

You are probably going to spend more energy than that just lugging around solar panels.

Seems not pessimistic enough to me. Realistically most people would capture on average, while the sun is up, about 100 watts if they covered their car in solar panels. A car needs at least 10 KW to cruise at 60 mph. This means you need to charge for 100 hours for 1 hour of driving. Actually 200 hours because you can't charge at night-time.

I have experience with solar and boats and it is generally the same problem.

No, you won't ever be able to power a boat or a car only on solar for long distances, unfortunately. Maybe if you are driving a few miles.

We can do what we do in the boating community - put a honda generator on top of it ;)

Solar panels on car is a good idea that sounds like a bad idea that sounds like a good idea.

It sounds like a good idea because if you can get your power from the sun you don't need to change.

It sounds like a bad idea because the charging rate is incredibly slow, especially compared to the rate a car can use energy. Solar power wouldn't noticeably increase the range, except for a very special-purpose non-street-legal vehicle.

However, it's actually a good idea because many people don't drive all that far in a given day. If you drive five miles to work, park in the sun, then drive back home, you might recover a pretty big chunk of that and not have to plug in quite as often or maybe not at all. The analysis is similar if you bike or take public transit to work and usually only go on medium-distance drives on the weekends.

> I used to run an extension cord out of my 2nd floor window

> More recently, I had been parking an electric car in my apartment's lot, and running an extension cord from the exercise room, out to the car. Then the apartment decided to close off those outlets.

Won't even get to what I am sure others have raised about safety issues. My question is why do you go to this effort? What in you makes you want to go to this extent in order to use an electric car?

Why not?

Personal contribution to the environment?

That's a big one for me. It's the largest thing you can probably do to reduce global warming, personally. EVs are also faster to accelerate, and more fun to drive.

Well, not the largest. I'm doing something better. I offset all my carbon and drive an ICE SUV. I'm actually carbon-negative every year.

I do contribute sulphur oxides and all that stuff, but global warming is driven less by those.

I would argue that we do not yet have a true way of offsetting carbon emissions.

Planting trees (that take decades to grow might or might not release the carbon again soon after) or helping other people emit less does not render your emissions harmless.

The only way that can work is to take it out of the atmosphere again for good. Is there is an offsetting option that I'm not aware of that does this?

I think it's the second largest. If you do pretty much any amount of flying, your carbon footprint will be dominated by that unless you drive an absurd amount.

You are aware that much of your electricity is generated from carbon-emitting power stations?

That depends heavily on where you live - CA, WA, NY have a high percentage of renewables - and even then, most fossil fuel power plants are still more efficient than an ICE car.

Because the cars are literally that much better than ICE. There's no comparison in the driving and ownership experience. Plugging in is not an inconvenience. Going to a gas station actually is an inconvenience and I'm dying to dump my second vehicle for an EV

Drastic reduction in pollution of my local environment.

Eventual huge reduction of CO2 emissions (once mining and other activities become fossil-fuel free enterprises). Small reduction now assuming local electricity sources are CO2-free.

Perhaps me aiming to reduce my CO2 emissions won't make a difference. I'm going to do it anyway. You should too.

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