Electric car: DIY!

[Frank]

I'd think you'd be able to cut a lot on the $3000 you reserved for the donor car - after all you don't need one with a working engine.

True. I have to go tour the scrapyards.

Or if you do take one with a working engine, do you think it would be at all possible to create something like a simplified hybrid? I.e. one where you could use the old, existing engine solely for the purpose of recharging your batteries, or maybe even use the clutch to disengage the existing engine and make it drive electric only?

I'm not an expert here, just thinking out loud. I guess much depends on how important weight is for you, but there are small cars out there that weigh just under 800kg including an engine.

Definitely possible. But, where do you leave all the batteries and the electric motor, if you leave the ICE in place? The easiest solution would probably be to use hub motors in the back wheels, and fill (half) the trunk with batteries.

 

[Simon F]

For an update:

First: batteries useable for electric vehicles are not the same as your run-off-the-mill car battery. They need to be able to deliver a lot of sustained power and to be drained regulary. A lot of abuse, so to say. That means that they are often bigger, or have a lower voltage. Batteries used in UPSes would work, but there are much better ones.

Isn't that why some designs use ultra capacitors in parallel with the batteries?

Incidentally, on the DIY front, did you see the "Scrapheap Challenge" episode (renamed "Junkyard Wars" in the US) where the teams had to build (from scrap) an electric offroader in 10(?)hrs?

 

[nelg]

Here Frank, this might be of interest to you.........

http://volt914.blogspot.com/

 

[WhiningKhan]

Isn't that why some designs use ultra capacitors in parallel with the batteries?

Capacitors won't help in getting high sustained power. They only help with peak transient response.

 

[_xxx_]

Ultracaps are there mainly to help you start the engine, since that's the moment where loads of current are drawn from the supply (huge curent peak causing a short voltage drop when you crank it).

 

[Simon F]

Capacitors won't help in getting high sustained power. They only help with peak transient response.

But surely most of the time you only need full power for short bursts**, say, from start to 60kph. If we assume a 1.5 tonne vehicle that would require about 208kJ of energy. According to this page, you can get, for example, a 48.6V, 144F module which should be able to store up to 170kJ. With a few of these and even only being able to extract 50% of the power, you should be fine.

Mind you, I've no idea how big/heavy these modules are!


**Unless you are boy racer.

 

[RussSchultz]

Their datasheet seems to suggest 500g/.5kg, if I got the right part number.

That seems really really light, so I'm suspicious.

edit: and I should be. Their largest module is more like 16kg.

 

[Mintmaster]

It wasn't wireless. It just had no contacts. It was a paddle system. You can transmit electricity over far greater distances wirelessly now though. MIT was doing something with it. Efficiency is crap though.

Sorry, that's what I meant. I still think you could have a charging system where you just park nearby and it automatically positions an induction loop close enough to get high efficiency in the transfer.

The gasoline is gone. You have to refill it with expensive fuel. Electricity if practically free in comparison. The expense is in the battery with an electric car and in the fuel for an ICE car. The point is energy density has absolutely nothing to do with it. Cost is orders of magnitude more important.

I missed your reply earlier, but energy density has everything to do with it, because my post was entirely about RANGE.

A whopping 565 pounds for only 4.5 gallons worth of range is inadequate for an electric car. That's why I agree with you that PHEV is the way to go. Of course we still have the problem of revamping the power grid to get off fossil fuels, so hopefully nuclear and/or some renewable miracle (CIGS solar and floating wind power are the only realistic possibilities, IMO) materializes.