10-Minute Electric Car Charging

Fast charging has been around (and used!) for about 15 years now. Used all the time in electric ground-support vehicles at airports. A year ago, the 123 batteries being sourced for the Phoneix electric truck were charged in under 15 minutes - enough for 150 mile of range. This was demonstrated in a public setting. There is no rocket science going on here. Shoving lots of power into batteries isn't something that needs new technology. Mostly it just needs huge conductors and a huge source (dump charging will likely be the best way of handling fast charging).

And then there's the fact that while this is exciting, and can be of some benefit for long-distance driving - there is no need for it in daily driving use.

I don't mean to dump on the parade....just I'm not sure what this is news.

 

Isn't fast charging also prone to cause battery defects if it's used a consistently? At least the battery charger I have for my sets of AA and AAA rechargeables says specifically that while it can charge fast, doing so repeatedly or regularly will be detrimental to the battery's life and performance.

Maybe it's different with the type and design of cells used in hybrid vehicles?

 

It is actually the opposite in many cases. As long as you manage the heat, fast charging can be better for the batteries than slow charging. Of course there is no standard for what is called "fast" or "slow." You can't compare the cheap AA chargers with fully-managed systems that will be in EVs. The main reason the small battery chargers will damange the cells is because of the generated heat that will occur.

Heat is the number one enemy. Control that, and you can charge amazingly fast with no ill effects. My car, with NiMH batteries, was designed to safely charge at 50A. But at 220V, it will only charge at about 17A, and that's how it was eventually put on the market. Purely for convenience of power that existed in the home.

 

How exactly do you plan to keep the battery cool in your Prius while charging?
(Intuition says that refrigeration would consume far more energy than it would be worth. However, if electricity was abundant and we were on "year 2000" mentality, we'd say "refrigerate the hell out of that sucker! Ain't technology grand?" If our only goal is to reduced CO2 emissions, we have clean evergy and nuke power, and coal power has been banned (yeah, I know, I'm being hypothetical with the coal) then go for it!)

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*Space satellites have fold-out solar panels. Why can't cars have solar panels that fold out when parked?

 

The design of the cell could be such that it radiates more heat. And even if you can't get rid of it, a managed charging system could at least vary the charge rate such that the heat doesn't go over a certain temp.

 

My sights are set a bit higher than charging a Prius battery. The Prius battery is already over-managed. I wouldn't worry about it.

If you have no need for that extra money you have sitting around, there is no reason you can't have this. Way better to have the panels on the roof of your house where they are always in the sun, always pointed at the right place, and not adding weight and complication to the car.

 

I remember using fast charging on my electric RC cards when I was young.

My question is, which is more energy efficient? Slow or fast charging?

If an ultra capacitor is required for the "dump" - there must be some energy conversion loss there (maybe negligable?).

What about on the battery itself? Does it use more total amps to charge it the same as a slow/trickle charge?

We know it gets hotter, but that's because the charge happens in 10 minutes. But is this waste heat more or less than the total waste heat during a much longer trickle charge?

I would also expect the power to cost more, as it's going to be at a commercial station and often be at peak hours.

 

In general, charging faster will be less efficient due to resistance - which in turn will raise the temperature of your conductors and raise resistance some more.

But since all batteries lose some amount of charge over time, charging too slow will also be less efficient.

So there is some sweet spot where charging will be most efficient - it will likely be a fairly wide range of currents.