Understanding EV charging - for the absolute beginner

[Ingineer]

After helping thousands of new LEAF owners understand the basics of EV charging, I've created some simple reading that only takes a few minutes of your time, and you'll come away with a much better understanding of electricity and charging.

I'd love some feedback. I'd like to keep it short and simple so busy people can absorb it, and only as technical as needed. I found that giving people a basic understanding of electricity is very empowering (hehe) as well!

-Phil

 

[TonyWilliams]

This needs some tweaking:

"This basically means you can draw 21kWh for one hour. A LEAF uses around 15-25kWh when driving on the highway"

 

[Ingineer]

Thanks Tony, I fixed it. Even the best of us sometimes swap the terms!

-Phil

 

[planet4ever]

Very good description, Phil. I only spotted one very minor slip: In the first paragraph after the Electricity/Water Analogy link you seem to be missing a word: "Since you now likely a new electric vehicle owner, ..."

One thing you have glossed over is the distinction between DC and AC. I agree that AC is conceptually harder to understand, and harder to extend the water analogy to. But I think once the basic concepts of amps, volts, and watts have soaked in (pun intended), people will buy that those same concepts apply to AC, even if they have to accept a bit of magic about what the electrons are doing. There does seem to be some confusion among neophytes at times as to why you can't just go from 240v to the QC port, as well as what transformers are and where they can be used. And there is no end of confusion about what a charger is and does compared to what an EVSE is and does.

Ray

 

[leafedbehind]

"This basically means you can draw 21kWh for one hour."

21kW for one hour.

 

[Ingineer]

Thanks everyone for finding all my Typos! Funny how I don't see them when I preuf reed! :lol:

Yeah, the AC thing is difficult. The field is vast, but I chose to keep it short. The water analogy is short enough so the ordinary layperson won't tune out. In this age of continuous distractions, I have to really work hard to be concise and still provide enough information. It was very difficult to get the various EVSE instruction sheets down to one page each, but I did it somehow!

-Phil

 

[mbender]

One more nit-picky "typo" of sorts that I would rephrase:

... your battery is 24kWh capacity,

I would say "... your battery has a capacity of 24kWh". 'Is XkWh capacity' sounds funny to me.

And along these same lines, somewhere in there you might consider roughly equating 7-8 kWh to one gallon of gas (or vice-versa), which would suggest that driving the LEAF is like driving a gas car of the same size but with a small gas tank (roughly 3 gallon), thus requiring somewhat more frequent "fill-ups".

 

[Sublime]

Maybe too much detail, but one of my fellow LEAF drivers asked my why charging at 1kW, 3kW, and 6kW takes about the same amount of time when over 80%. I told him to imagine filling up a 2 liter bottle. If you're filling it up by catching water dripping from a faucet you don't have to slow down as you reach the top. If you have it turned up full blast, you'll make a mess if you don't slow the flow down as you approach the top.

 

[ksnogas2112]

Looks good Phil. I agree with the previous posts about is vs has capacity.

 

[adric22]

One question I often get is why electric cars can't charge faster from a 120V outlet. They say "they need to improve that so I don't have to buy an expensive charging station." This is hard to explain for somebody who doesn't know a lot about electricity. So the way I try to explain it is by comparing to filling up a swimming pool with a garden hose and a higher power charging station is like filling it with a fire-hose. Their request is that the car manufacturer address the problem as if it is their fault. So I make a comparison saying that is like complaining to the swimming pool manufacturer that it is their fault it takes so long to fill the pool with a garden hose.

 

[Ingineer]

One question I often get is why electric cars can't charge faster from a 120V outlet. They say "they need to improve that so I don't have to buy an expensive charging station." This is hard to explain for somebody who doesn't know a lot about electricity. So the way I try to explain it is by comparing to filling up a swimming pool with a garden hose and a higher power charging station is like filling it with a fire-hose. Their request is that the car manufacturer address the problem as if it is their fault. So I make a comparison saying that is like complaining to the swimming pool manufacturer that it is their fault it takes so long to fill the pool with a garden hose.

Yes, we get this all the time, so that is why I specifically address the 12 amp limit from a 120 volt outlet.

Since most home 120 volt outlets are only capable of sustaining about 12 amps continuously (safely), you are limited to 1.44kW or 1440 watts. This is why you absolutely need a 240 volt outlet to get faster charging.

The water analogy is always useful, that's why I included a good one!

-Phil

 

[mbender]

Couple of other observations which you might consider working in:

• A kWh can be roughly thought of as one pint of gasoline.
• Maybe mention their corresponding average prices of $0.10-0.20 vs $0.40-$0.50
• The confusion that comes from the word Watt imho is that it sounds like a 'noun',
  or that it measures a noun/thing, but it's really more of a 'verb', a measure of speed, essentially.
  I imagine this is confusing to beginners and explains why even those who know better mix up kW and kWh!

 

[ERG4ALL]

Maybe to address the DC vs AC issue it might be worthwhile to liken DC as in the water analogy that each electron travels along the wire until it finally exits to do work. Whereas the energy transferred in the AC circuit is more like those toys with the hanging steel balls (Newton's cradle) that when the energy travels along the balls and the last ball is free to swing upward and then come back down and transfer the energy to the starting ball. Thus, the electrons are are really banging back and forth at 60 Hz. I dunno maybe it is just as well left alone for the average guy.