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by happenstance 5978 days ago
Lots of people do their own EV conversions from ICE (internal combustion engine) cars. Trouble is, up until now they've all used lead acid batteries (and as such, were heavy and didn't have great range).

The next step -- and what I'm really interested to start seeing -- is homebrew EV's using Lithium Ion batteries. I think this is going to be the next step.
2 comments
frankus 5978 days ago
Lithium ion still has a pretty steep early adopter tax, and they're not as forgiving as lead-acid (Overcharging lead-acid batteries ruins your $2k pack. Overcharging lithium ion batteries will ruin your $20k pack and can easily burn up your car and your house).

But they're very much coming down in price. In RC-plane sized packs, lithium polymer packs (with a 5C discharge rating) are down to about $500/kWh retail. A minimum viable pack for a very light car might be five kilowatt-hours (and might only weigh 70 pounds, a little over a tenth the weight of lead-acid).

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proee 5978 days ago
The advancement of motor and power convert technology is also worth noting. AC motors are a huge upgrade over the old dc motors that used brushes.
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frankus 5978 days ago
AC motors are really great if you're building a drivetrain from scratch. You get a cheaper gearbox (single speed, no reverse) and a cheaper motor (theoretically) by paying for roughly six times the electronics (although you can divide the current capability of everything by the square root of three). And it drives just like an automatic transmission, only better.

But with a conversion vehicle the gearbox comes for free with the donor car, and it's typically more work to integrate a single-speed drive than to just adapt the motor housing and shaft to the transmission bellhousing and flywheel. And you're not paying the early adopter tax that's still present on AC drivetrains.

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happenstance 5978 days ago
DC motors are very efficient, so, I'd have to see some numbers to buy that.

Also, a big plus for DC motors is that the controllers are simpler. AC motors require a high-power adjustable-frequency inverter.

The only downside of common standard DC motors that I know of is that you have to change the brushes every n years, which I'll gladly take over oil changes. :)

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proee 5978 days ago
Well you forced me into a google search. Here's a good read on dc vs ac type motors used in EVs.

http://www.teslamotors.com/blog4/?p=45

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happenstance 5978 days ago
Thanks for the link.

Though, I still tend to gravitate toward the simplest solutions, and in this case, a series-wound brushed motor is about as simple as it gets.

Regular DC motors have heavy and strong magnets (more expensive), but the series-wound motors are just wires (and, FWICT, a bit less efficient).

Regarding brushless, I'm sure they're quieter and require less maintenance, but they still are more complex than the series-wound DC.

I suppose the AC induction motors have their place, but for the DIY crowd, I think many will stick with the basics.

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