Simple Cheap Hybrid Car? (DIY)

[chrisoverson]

Hi all!

I'm trying to modify my car to get max MPG, and I've come to the conclusion that because of where I drive (mostly short, urban trips with lots of hills with occasional long highway trips a couple of times a year) some form of electric/petrol hybrid would be a good option for me.

I don't want to sell my car, and can't afford another. My car weighs around 1070kg, plus say around 200 for me and a couple of passengers.

My main target for this is creeping forward at very low speeds in traffic (5mph maybe a little more) and cruising at highway speeds around 56mph. I'll be working to improve aerodynamics on my car where possible, but according to a horsepower calculator I used that factors in drag and weight I need around 7-10hp to keep the car moving at this speed.

Basically, I want to make this as cheaply as possible. I haven't been able to source any motors out of a scrapped hybrid, and all the ones I see online are far too expensive for me.

Ideally I want to make it run from a seperate battery in the boot (I'm thinking start with 12v lead-acid because I have a couple of spares already) which I could charge from home and via solar panel, and also maybe regenerative breaking if I get that far.

Electronics are not a major concern for me but I am not the best at mechanics, so I will be getting help at installing anything that I need. My first thought was the starter motor. This is capable of providing around 20hp, and is already installed and ready to go in a sense. Could I use this to power the car?

As I understand it the problem with starter motors is they are designed to operate for very short periods of time before they overheat, which is understandable. If I added enough cooling to the starter motor would it be possible to make it drive the car? Also if I used one to turn the wheels directly rather than spinning the engine and gearbox, controlling the speed correctly would that be doable?

If that won't work, can anyone offer a suggestion as to where I should look next... I'm really interested in doing this. I'm going to be essentially making my own engine management and control combined with a computer monitoring speeds, gradients, fuel usage, temperatures and all sorts of other things to calculate what to do in order to optimize the engine and also switch between the two or maybe use both!

Any advice would be great here guys

Thanks!

[MetroMPG]

Welcome to the forum.

The "DIY hybrid" is a very unicorn-ish type of project: often discussed, rarely seen (due to the challenges, including cost).

You might want to have a look at the following recent discussion - lots of examples of approaches and ideas:

http://ecomodder.com/forum/showthrea...rid-20075.html

[GRU]

i think a cheaper way would be to add a electric motor to the car (let's say attach the motor to a rear wheel of a front wheel drive car, or to a driveshaft on a RWD car.) so use the gas motor for acceleration and high speeds but turn off the motor at low speeds when you can engage the electric motor. It's an idea but it would be much cheaper than converting the whole car to electric

[Ryland]

A 10hp motor running off 12v is going to need a 1000 amp speed controller and huge cables, you are also going to need a 12v battery that can handle that 1000 amp draw, even a pair of golf cart batteries, at 210 amp hours, 6v each giving a total of 12v is only going to be able to give you 10hp for around 6 to 10 minutes and is going to need 18mm cable or 3/4" copper cable, or you can bump the voltage up and shrink the cable size and the number of amps needed, a much better idea because you are not going to find a 10hp 12v motor, a 72v motor is about as low of voltage as you are going to be able to get away with, then you need to figure out how you get that motor to connect to your wheels, it can either connect via the engine or it can bypass the engine, they each have their advantages and disadvantages and you need to look at your vehicle and figure out what will work.
You also do need a speed controller, otherwise the motor is on full blast, it's like revving your engine and shifting in to gear, you will brake stuff!

[pete c]

I think that electric propulsion to push you along at cruising speeds is probably off the table, given your budget. A smaller motor used to nudge you along in a traffic jam might be doable. A golf cart motor might work for this.

[chrisoverson]

Thanks a lot for the replies guys

Ok so I understand why you can't use a 12v motor... it'd just draw far too many amps. A shame really I have 2 spare car batteries .

So, where could I hope to find a suitable motor and battery?

I like the idea of attaching straight to the back wheels, would only attaching to one do the trick or would I have to use both?

I should add the car is 1.8l petrol and front wheel drive... the rear wheels are just pulled along spinning on their wheel hubs .

I had thought of welding some kind of toothed disc onto the hub that then connects with whatever motor I end up using, rather than building it straight into the wheel... does this sound like a good plan?

Thanks!

[pete c]

electric assist to a rear wheel would be ideal, but doing it is a bit tricky, especially for a guy self described as not the best at mechanics.

i don't suppose your car comes in a AWD configuration? If it did, you might be able to score a rear end from such a vehicle and bolt it in. Getting a rear from a similar sized RWD car could work, but, would require a fair bit of fabrication skills.

[chrisoverson]

No it doesn't I'm afraid. It's a small hatchback available in FWD only.

I can understand that this probably isn't the best idea for someone who is not very good in this area, but it would make a great addition to my project. I plan on making this car able to do upwards of 100mpg (UK) so around 83mpg US on the highway, and as much as possible around town. A little ambitious I know, but it's a nice round number to aim for.

My current best is around 57mpg at an average speed of 34mph using P&G without turning off the engine... I'll try it today with the engine off during glides to see what I get.

The most economical version of my vehicle is the diesel which is a 2.0 litre turbo... I keep wondering whether I should try and tweak that instead, as it has 63mpg highway as standard according to the book.

So, what's my best option here? Try to find an electric motor from somewhere and work out how to fit it to a rear wheel and build a motor controller... or take out parts from a car already using electric/hybrid technology (probably very expensive). I'll be doing as much as possible to optimise my current engine, but building in new parts not designed for the car is something I need help with xP.

[Ryland]

The motor from an existing hybrid is going to be the hardest to use because all of them that I've seen at least are designed to work as a whole unit, they are often built in to the transmission of the car, so removing that one part and putting it in something else is not practical, just like replacing the motor in a hybrid with an off the shelf motor would be nearly impossible.

Again, your first step is going to be figuring out where a motor can attach, as much as driving a rear wheel or both rear wheels seems like a great idea, it will also mean that you are designing and building a whole drive train for the rear of your car! the rear hubs that you have are not designed to be driven and if you pull a rear wheel off I'm going to bet that there is not much extra space back there, so while it would be the best, it's also going to be the hardest.
Because the suspension of the car has to move with the bumps in the road, the closer to a wheel you get the harder it is going to be to build a mechanical connection, that is why if a 4 wheel drive version of your car was built it would be easier, you buy a used rear wheel drive train and suddenly it's putting the drive shaft for the rear wheels in a nice stationary location, but that is not the case with the vehicle you have.
A mild hybrid might be the best idea, it would be the easiest for sure! open the hood on your car and look for a location on the engine where a power steering pump, air conditioner compressor, or something else could bolt on and have a clean straight shot to the crank shaft pulley, the electric motor would still need the gas engine turning while the electric motor is helping the car along, but it will be more like driving with a tail wind or down hill all of the time.
Also the two car batteries you have are most likely starting batteries, not deep cycle batteries and they are most likely different ages and sizes, so your total usefulness would be limited by the smallest or oldest battery, the rest of the other one would be dead weight.

[nimblemotors]

Why haven't you told us which car you have? and pics too!

Probably the cheapest way without too much modification is to add on a 5th electric powered wheel that raises and lowers. Lower it for stop-n-go, raise it for the highway. This was done by a guy who I can't remember on his Honda Insight. Use an electric scooter, the rear wheel and the controllers, etc.
Find one with a wrecked front-end.

OK, I searched and found it for you,
http://99mpg.com/ProjectCars/ewheelforanyvehicl/

Originally Posted by chrisoverson

Hi all!

I'm trying to modify my car to get max MPG, and I've come to the conclusion that because of where I drive (mostly short, urban trips with lots of hills with occasional long highway trips a couple of times a year) some form of electric/petrol hybrid would be a good option for me.

I don't want to sell my car, and can't afford another. My car weighs around 1070kg, plus say around 200 for me and a couple of passengers.

My main target for this is creeping forward at very low speeds in traffic (5mph maybe a little more) and cruising at highway speeds around 56mph. I'll be working to improve aerodynamics on my car where possible, but according to a horsepower calculator I used that factors in drag and weight I need around 7-10hp to keep the car moving at this speed.

Basically, I want to make this as cheaply as possible. I haven't been able to source any motors out of a scrapped hybrid, and all the ones I see online are far too expensive for me.

Ideally I want to make it run from a seperate battery in the boot (I'm thinking start with 12v lead-acid because I have a couple of spares already) which I could charge from home and via solar panel, and also maybe regenerative breaking if I get that far.

Electronics are not a major concern for me but I am not the best at mechanics, so I will be getting help at installing anything that I need. My first thought was the starter motor. This is capable of providing around 20hp, and is already installed and ready to go in a sense. Could I use this to power the car?

As I understand it the problem with starter motors is they are designed to operate for very short periods of time before they overheat, which is understandable. If I added enough cooling to the starter motor would it be possible to make it drive the car? Also if I used one to turn the wheels directly rather than spinning the engine and gearbox, controlling the speed correctly would that be doable?

If that won't work, can anyone offer a suggestion as to where I should look next... I'm really interested in doing this. I'm going to be essentially making my own engine management and control combined with a computer monitoring speeds, gradients, fuel usage, temperatures and all sorts of other things to calculate what to do in order to optimize the engine and also switch between the two or maybe use both!

Any advice would be great here guys

Thanks!