Fuel Efficiency and Hybrid Cars

George,

I've been dreaming of making a lightweight electric 4-wheel transport for some time. As far as I can tell there are two approaches that can be taken:

1. Elecrtric car technology. There are loads of DIY electric car conversion options. One can buy the electric motors, controllers and batteries without difficulty - except to the wallet. Powerful motors and controllers capable of driving fully sized standard cars (e.g. typical hatchback or small/medium sized saloon) are freely available for a fee. The best motors cost between £2k and £3k. The associated controllers (the real cleverness in the solution) cost another £1500 to £3k. All this seems reasonable until you consider batteries. Standard lead/acid batteries cost a few hundred quid for a short (40mile) range. The most expensive are lithium ion polymer and you could spend many thousands (anything up to £30k) for a reasonable range. The LI batteries are lighter, store more and more efficient at storing the energy with lower energy loss rate as well as better ambient temperature handling but they sell in low volume which is why they're so expensive. Once they start selling in earnest, their price'll tumble, but in the meantime they remain expensive. Li-Ion is the technology used in the Prius and Honda Civic, but these hybrid solutions are more add-ons to the underlying standard IC car rather than the genuine motive power. This is why their numbers could be better. Incidentally, you can have a hybrid modified so it can be recharged at home on the electricity circuit (rather than just by the petrol engine) which makes it very much more efficient...!

2. Electric bike technology. Start with the components that make an electric pedal-assisted bicycle and build a light tubular 4-wheel frame with two electric bicycle motors, very basic seats, some pedals (just in case) and a few bicycle Li-Ion battery packs. Provided you use bicycle parts and tubing, everything remains very light. Since you may wish to go 40 miles (typical commuter distance is 10 miles), and the quadricycle (although that's a different thing really) needs to carry two up as well as the extra weight of the chassis, two motors are required as would be more than two battery packs. In pursuit of lightness, one uses tarpaulin, perspex - all the usual materials used in soft top sports cars - for the 'cabin'. I followed this idea in my head almost to the point where I thought I could design the whole thing, then dropped it since I have no idea when it comes to braising tubes and working out the stresses on the vehicle, and seeing things like this through to the end aren't my forte'.

For more info and hoping I'm not breaking forum rules, have a look at the DIY electric car forums (which includes bike info) on:

http://www.diyelectriccar.com/forums/

quote:

They are in effect an invalid carriage with 4 wheels

Ouch! We really shouldn't use that word, sorry. I have a friend with MS & being in a wheelchair doesn't make her "invalid" i.e. "not valid".
These old expressions really need to be binned.
The other one that gets me is is "Falling pregnant". Becoming pregnant does not make a "Fallen" woman. Amazing how often you still hear it.
Okay...carry on.

here's my offering on this topic: diesel hybrid. a viable technology that's here now, and should be able to produce very high mpg. (battery charging is a non-issue w/ hybrids, btw, though there are other problems.)

quote:

Originally posted by Frank Abela:
George,

I've been dreaming of making a lightweight electric 4-wheel transport for some time. As far as I can tell there are two approaches that can be taken:

1. ...

2. Electric bike technology. Start with the components that make an electric pedal-assisted bicycle and build a light tubular 4-wheel frame with two electric bicycle motors, very basic seats, some pedals (just in case) and a few bicycle Li-Ion battery packs. Provided you use bicycle parts and tubing, everything remains very light. Since you may wish to go 40 miles (typical commuter distance is 10 miles), and the quadricycle (although that's a different thing really) needs to carry two up as well as the extra weight of the chassis, two motors are required as would be more than two battery packs. In pursuit of lightness, one uses tarpaulin, perspex - all the usual materials used in soft top sports cars - for the 'cabin'. I followed this idea in my head almost to the point where I thought I could design the whole thing, then dropped it since I have no idea when it comes to braising tubes and working out the stresses on the vehicle, and seeing things like this through to the end aren't my forte'.

Regards,
Frank.

Dear Frank,

This is exactly the route I would go.

It would be a true ultra light short-haul, low speed vehicle. And I must admit that I was happy to consider keeping pedal assistance!

Really all you need is a windscreen, and not necessarily side screens, as roll-down PVC could be used in wet weather...

I would attach a solar cell array on the full-length flat roof so that for much of the year the charging would be minimal.

Really it would cost around £1000, for a one off, if I left off the solar cell array. I dream things up. I have an idea for a turntable, which would be very good, but seems a bit pointless, as it is like reinventing the wheel! But this would be different, and save a fortune on an over specified [under the circumstances for me] long distance high speed and significantly heavy family saloon, which in reality - mine - usually only gets used for the occasional very long run, or pottering round if I am too lazy to walk or ride the bike.

I could plan the long trips differently, and then do away, permanently, with a normal style of car!

That would be my ambition. A well-made frame would be able to cope with any modifications that improving technologies might throw up over time!

ATB from George

Something like this then...but an electric version

George,

It might be a bit more expensive. Standard bike kits cost around £300 - £500. You would need at least two (one per rear wheel ) or possibly more (you could have a central powered fifth wheel at the back, or you could have 4-wheel drive). You'd need this because the added weight of the extra bits equates to more than two bicycles which is why the 2 sets would be the minimum. I would also add extra battery packs which are easily available to guarantee range and power.

The solar panel is a stretch. It may be possible to do this but I have not seen any models that are easily and cheaply available. The panel would also have to plug into a charger on the vehicle which adds weight and this would have to be compatible with the rest of the electronics so I'm not convinced it's a go, but it was also something I was thinking about.

The rest is all standard technology and since bike batteries are either Lithium-Ion (£500 - £800 kits) or Nickel-Cadmium (£300 - £500 kits) they have a very high specific energy storage and are the most efficient solutions available by weight. They're also quite common so replacements are easy. This is why I was getting quite interested in this solution. The downside is a maximum speed of around 15 mph. Legal electric bikes cannot go above 15mph unassisted and in traffic - even in the city - this is a problem. You need to be able to keep up with the traffic which really means being capable of hitting 30mph.

There are electric bike systems which can allow this kind of performance, but then you use at least twice the energy, possibly more, and the whole tyre proposition becomes more difficult. If you use standard bike wheels (they are the lightest after all) then these are really designed for leaning into corners so they have quite high profiles. I had thought that perhaps a system could be devised for cornering such that when you turn the wheel (or bars or whatever), the wheels would not only turn but lean in the direction of change. This would allow them to be used in the way they were designed to be used and get around any worries such as tyres coming off their rims. Of course, the rears have to do the same too. The linkage proposition is a bit messy, to say the least, but car or motorcycle wheels are so much heavier that using them is just not sensible.

Maybe I'm making it too complicated...! I just feel that the 15mph restriction makes life difficult. If people see a lightweight vehicle the size of a car (or thereabouts), they expect it to move in a particular way.

quote:

Originally posted by av in bc:
you and your FORD FALCON XR6 Turbo will get maybe 12L per 100 (if you're lucky those estimates are always optimistic and misleading)

Heh heh heh! I rented one of these and the fuel consumption is very much dependent on your driving style and traffic condition. If you like to drag from light to light then you will most likely average 20 litres to 100km. If you drive to the condition, and adhere to the road speed limit then you can get 10 litres per 100 km. This is my experience and my style of driving.

What increases the fuel consumption is the stop start in the city. This is where the savings in the prius comes in. The prius is not more economical when on motorway but is in inner city run, even compared to diesel. Plus there is this charge called RUC in some countries for diesel cars, which makes it not economical to run a diesel car in dollar terms per km travelled unless you are a heavy vehicle with a large engine capacity.

The up shot is you get a car which suit your needs. If you only travel to work and back, not carrying any luggage etc, then a small petrol or diesel will be the way to go. Unless you can get an electric car to work and charge it at work then drive home!

Each to their own. I get free electricity now as my solar panels give me more energy than I can use!

quote:

Originally posted by wellyspyder:

quote:

Originally posted by av in bc:
you and your FORD FALCON XR6 Turbo will get maybe 12L per 100 (if you're lucky those estimates are always optimistic and misleading)

Heh heh heh! I rented one of these and the fuel consumption is very much dependent on your driving style and traffic condition. If you like to drag from light to light then you will most likely average 20 litres to 100km. If you drive to the condition, and adhere to the road speed limit then you can get 10 litres per 100 km. This is my experience and my style of driving.

You must be light footed then - I got 10L per 100 when I rented a non-turbo XR6
Davo, the G6ET is top of my wish list - pity the darn things aren't here yet.

wellspyder,

BMW's latest cars have StopStart. They kill the engine when stoppsed and start it again when you lift the clutch (yes, manual only I believe, hich is more economical anyway). Therefore the inner city driving advantage of the Prius is significantly lower against a BMW with StopStart installed.

quote:

BMW's latest cars have StopStart.

My daughter used to have a 1984 VW Polo that swithced off the engine if you stopped (at traffic lights or a level crossing or in a queue) and selected neutral. Soon as you pressed the clutch pedal in, the engine started and off you went.

Obviously not BMW territory, but many of these concepts have been around for decades.

Cheers

Don

You're right Don, a very old idea. However, starter motors draw a considerable current and one needs to consider the energy needed to power the significant number of start-ups needed during town driving.

There's probably an advantage but perhaps not as much as might be assumed.

I don't like the BMW image personally, but I have to admit that for a big executive saloon, the figures for the 5 series diesel are extremely impressive. This is where the future lies if they can do this sort of thing. Look at the Lexus Hybrid and I'll be pretty amazed if they manage to sell a single one. The fuel consumption figures are pathetic.

I don't think the Lexus 400h etc. were supposed to be fuel efficient. A friend who used to work for Lexus was told by his superiors that the target market was people who wanted to drive a 4x4 around London without having to pay Red Ken the congestion charge!

I find it hard to believe that Lexus develop hybrid technology & launch a car onto the world market tailored around a local tax in a single city.

Last year, we were changing our diesel Land Cruiser which we use for towing a caravan (stop sniggering!).

We took the hybrid Lexus 400 for a test drive, and were very impressed. Fuel consumption was on a par with our Land Cruiser and it was very quick. It was spooky to drive because it was almost totally silent. Lots of gadgets. The dealer was a very nice chap, and left us to decide what we thought.

I said I'd give him a call later in the day, with the intention of seeing if I could do a good deal on their demonstrator. Anyway, when we arrived home there was a message from the dealer to give him a call back. On talking to him he explained that he was a bit worried about us using the vehicle for towing our rather heavy caravan, because the extra torque required would almost certainly mean that the Lexus would be running on both electric and the petrol engine, giving absolutely lousy fuel consumption as well as increased noise.

Good on him for being so honest, and I told him it seemed to me the car was really designed for mostly pootling around town, which he agreed with.

quote:

Originally posted by Ewan Aye:
I find it hard to believe that Lexus develop hybrid technology & launch a car onto the world market tailored around a local tax in a single city.

I'm sure it wasn't, but as most of the road tests of it said that the hybrid drive only worked without the petrol engine under 25 mph it was clearly designed for cities with obscenely slow moving traffic, it's quite easy to see why Lexus UK would focus on London.

Heavy vehicles, which most "4 wheel drive trucks" are, get better fuel economy when powered by diesel engines. That is why big rigs are mainly powered by diesels. The engines have more torque and use less fuel.

Power to all 4 wheels constantly will also decrease fuel economy!