Deflated Prius owner.

[biteme]

I was having a chat with a mate and he reckons they've got the whole hybrid thing the wrong way about.

He reckons it should be purely electrically powered with a tiny diesel acting as a giant alternator to charge to batteries. Not sure if it would work though.

B

[GSRman]

i get about 270km from 54L around townish, a fair bit better on the hyway, but still not economical..

[Asteroid]

I was having a chat with a mate and he reckons they've got the whole hybrid thing the wrong way about.

He reckons it should be purely electrically powered with a tiny diesel acting as a giant alternator to charge to batteries. Not sure if it would work though.

B

Like in the same manner as a diesel train? Interesting...

[Billzilla]

I was having a chat with a mate and he reckons they've got the whole hybrid thing the wrong way about.

He reckons it should be purely electrically powered with a tiny diesel acting as a giant alternator to charge to batteries. Not sure if it would work though.

B

That's what I reckon as well.

My idea is based on averages for driving around town. In typical city traffic you need very little power, on average, so I suspect in reality you only need a very small petrol engine to provide that average. And the electric motors & batteries do the rest.
All the electric cars I've seen have a big expensive controller box, and my idea eliminates that for a much smaller and cheaper one, by using something like 20 small batteries and as you push down on the accelerator relays click-in to add more and more batteries as needed. Only the first battery power runs through the electric controller, to modulate the power than last 5% to smooth out the changes in power applied.
The small 100cc-odd petrol engine would drive a big alternator, and that would charge up the batteries not being use by another set of replays, etc.
I figure all that would weigh maybe slightly more but cost a crapload less than something like the Prius, but go as well and use far less fuel.
I reckon something in excess of 100mpg is quite possible.



Speaking of the Prius, there's a trick that the better drivers use on them on the highway that really helps the fuel economy, but it means going slower than most traffic. They very gently use the throttle to keep the petrol engine cutting in & out every few minutes. They get something better than 3-4 l/100km that way.
But it's too slow for most highways.

[Zac]

so a 30% efficient engine producing 20hp would drive a 75% efficient alternator. dunno about the electricity side but that doesn't sound like the greatest start.

and how big would those relays be for all those batteries?

[fdrx7]

It's called a series hybrid and I just walked away from working on a 15 tonne bus powered by one then. We use a 2.5 litre diesel to charge the batteries when they're needed. Other than that it just punts around on the batteries all day.

Haven't tested fuel economy yet but it's a damn sight better than a conventional bus. The other bonus with a series hybrid is that the engine can switch on - run at peak BSFC to charge the batteries then shut off. Not spend the whole day hunting around in the thirsty parts of a map.

[Billzilla]

so a 30% efficient engine producing 20hp would drive a 75% efficient alternator. dunno about the electricity side but that doesn't sound like the greatest start.

and how big would those relays be for all those batteries?

No it'd be a lot more efficient that 30% - I'd probably use a small diesel and since it'd only be running at the same revs it could be optimised quite a lot.
Certainly far more than a Prius.

The relays wouldn't have to be too big, as they are only connected to relatively small batteries. There's also only a tiny power loss when using relays, compared to the heat & power loss of the big controller boxes.

[fdrx7]

so a 30% efficient engine producing 20hp would drive a 75% efficient alternator. dunno about the electricity side but that doesn't sound like the greatest start.

and how big would those relays be for all those batteries?

Doesn't work like that. Engine runs at peak efficiency when on. Normal engines average around double to triple BSFC. So they _drink_ by comparason. Generator runs at close to 98% efficiency. If you're directly feeding the engine, it can run at close to 98% efficiency again. Charging and discharging the batteries brings with it a big loss, but that is more than made up for by regenerative braking.

I'm far more interested in what's planned for a major UK 'kit car' job....

[fdrx7]

Oh and bill the relays thing is not a goer. The motors work off AC drive (yeah even the big 'DC' motors you see in electric drag cars have inverters built in). The best way to regulate flow from the batteries to AC-eating motors is switching with IGBTs. Essentially big solid-state relays that don't arc over and burn contacts like relays do. They still have on-resistance losses that cause losses, but are a much better choice than relays stepping into an inverter that's there anyway

[Billzilla]

Oh and bill the relays thing is not a goer. The motors work off AC drive (yeah even the big 'DC' motors you see in electric drag cars have inverters built in). The best way to regulate flow from the batteries to AC-eating motors is switching with IGBTs. Essentially big solid-state relays that don't arc over and burn contacts like relays do. They still have on-resistance losses that cause losses, but are a much better choice than relays stepping into an inverter that's there anyway

I was thinking of a permanent magnet brushless DC motor.

[Zac]

Sounds much more promising now!

I'm far more interested in what's planned for a major UK 'kit car' job....

Tell me more..
Have you seen what Martin Ogilvy is doing for the Brit Hillclimb? I haven't heard much myself but he is building a dedicated 4WD electric racecar.

[fdrx7]

Bill doesn't matter. BLDC motors effectively 'create' a AC signal by switching DC onto the inductive windings. So you still need switching technology, so you still need IGBTs.....

Zac,
Happy to. But some other time - off home now

[Billzilla]

Bill doesn't matter. BLDC motors effectively 'create' a AC signal by switching DC onto the inductive windings. So you still need switching technology, so you still need IGBTs.....

Ta - re-think time!

[smellytofu]

With just diesel generators, if you did happen to drain the batteries to the point where it can't or very slowly moves the car (probably the diesel motor kicks in to prevent this anyway like the Prius), how long would it take for the batteries to get to a point where it's capable to providing acceptable performance?

[rj_astra]

Don't know if this has been mentioned. SOunds like you want to built the Chevy Volt. http://www.chevrolet.com/electriccar/

Opel have some affordable hybrids coming to market. I can see that the Japanese lead in the area will evaporate pretty soon as the Europeans are mixing diesel and hybrid technology.

http://www.autoblog.com/2007/08/23/f...ybrid-concept/

Hmmm. Imagine a LPG/Hyrbid Territory. How cheap would that be to run!