Simple Cheap Hybrid Car? (DIY)
 

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!

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

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

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!

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.

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 :p.

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 :p.

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!

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.

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.

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.

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/

I think Ryland's suggestion will probably work best for you. It does eliminate the ability to run on electric only in stop and go heavy traffic, but, it is far simpler, mechanically speaking.

I think a fairly high voltage motor/generator/starter mounted where the alternator currently lives could work. Being an electronics type, you should be able to come up with some sort of engine stop/start system which would maximize city mileage.

You should also be able to regulate whatever voltage you use down to 12 vdc to handle the rest of the car's needs.

Good luck with it, Chris. Show us that an englishman can actually make a functional auto electric system (insert obligatory Lucas joke here).

lmao ;).

Well my car was designed and built in England so that's a start.

The car is a 1998 Rover 218 iS weighing 1032kg, 1.8 litre naturally aspirated K-Series engine, Aluminium head and block with Twin Overhead Cams.

Manual gearbox with 5 forward gears and one reverse gear so pretty standard. 4 spark plugs, multipoint fuel injection controlled by the Rover MEMS1.9 engine management system, which is OBDI.

The car has power asisted steering (belt driven), alternator belt driven obviously, DC fan which hardly ever kicks in, and no air conditioning, although there is an air-con version of it.

Standard highway rating: 48.4mpg, city rating: 27mpg. My current best is 57.8mpg with an average speed of around 34mph.

Drag coefficient: 0.330cd
Frontal Area: 2.00 square metres
Cda: 0.66

Current gearing puts the engine speed at 55mph in 5th at 2488rpm

Here's the car:

http://nibble.cc/car/april2.jpg

http://clippyshare.nibble.cc/?id=129801805988312587

Engine bay:

http://clippyshare.nibble.cc/?id=129801807097236014

http://clippyshare.nibble.cc/?id=129801807451296265

My cone air filter:

http://clippyshare.nibble.cc/?id=129801807219953033



My grille block test:

http://clippyshare.nibble.cc/?id=129793095395030158

Here's my DIY arduino based fuel monitor and MPG calculator:

http://clippyshare.nibble.cc/?id=129779602810485146

Thanks all for the current ideas... I'm liking the mild hybrid idea best, the idea of a 5th wheel would be a little too rediculous looking for me. I want to preserve the looks of the car where possible as I have future design plans for it to modernise it a bit. If I was absolutely dedicated to MPG to the extent I'd make such huge alterations I'd just change cars to something more economical :). Even if the other options are more complex... I'd rather go that way. I'm aiming for a more professional OEM outside appearance really.

So if I were to attach an electric motor to the the engine, I could easily mount it where the power steering goes... but would it be able to assist the engine and be belt driven? If so, I'd be interested in this idea as I was thinking of converting the power steering to an electrical pump anyway as I could turn it on/off as I wanted.

I have a better idea for an energy source for steering.

It's called arm assist. They used to use it on vehicles much larger than yours, back when men were men.

The auto industry seems to have convinced us all that we need power assist for braking and steering. It certainly is nice in an S class benz, but, IMO it is a waste of money in a 2000 lb compact.

So, convert it over to powerful steering or I will have to taunt you with nancy boy jokes!

I suppose maintaining vacuum assist for braking is OK as it is basically free power and will allow you to conserve energy for those parking lot steering workouts. Also, I assume you may have some sort of ABS which probably needs to have the vac. assist to function properly.

Personally, I wish I could buy a modern subcompact with absolutely no power assist like I had in my '78 fiesta. I think such models exist for you euros, but not for us obese lazy colonists.

lol fair enough :).

I used to have no power steering on my first car, a Peugeot 106 1.5 diesel. I imagine the efficiency on that was pretty good and I've thought about getting another one but the ride and comfort was shocking, along with the build quality.

I can drive my car without power steering, and I would hapily sacrifice it for fuel economy, but if it only gives me something rediculous like 1mpg then I'd rather keep it ;) as it does get bloody heavy and 90% of my driving is in town.

It's bloody heavy because you are having to manually drag all that power assist stuff around. I could do the same with my old 91 accord. I can not do it with my ranger or my wife's sonata. Parking lot steering with them most definitely requires assist.

Is power steering an option with your car? If it is, you might be able to find a manual steering rack. Or you could just step up to the challenge and enjoy the popeye like forearms that you will soon develop.

xD no it comes as standard on all of them. To be honest I prefer the idea of electric power steering that I can turn on or off as I need it. In the mean time if I can't find such a pump I'm happy to go without and make like popeye :).

So, back to the original point, could I put on a motor in place of the power steering? If so would the belt be able to transfer enough energy to the engine to make a positive difference...

A key to the mild hybrid idea is to replace the starter and alternator with a single motor-generator that can assist the engine. It adds no additional weight and is a simpler design. Strange it still isn't common even today.
What it allows is to tune the engine to have less low-RPM torque.

If you just ADD the weight of the motor, and don't retune the engine to take full advantage of the electric power, I don't think the gains will be much, since even the tuned versions it isn't that big.
For stop-n-go, a Prius can yeild large improvement because the engine isn't running at all, and braking can put back the power used. You get none of that with the mild hybrid and certainly not the add-on approach.
Swap your car with a Prius, it requires no work or mechanical skill at all and you get 50mpg, and not only does it look oem, it IS oem.
You will not be able to do yourself anything better and cheaper, without changing cars and/or engines.

Ok so what you're saying is the mild hybrid idea is doable on my car but I won't see gains without tuning the engine properly, and any gains I see will still be less than having a hybrid car anyway.

Well I don't really want to just switch to a Toyota Prius just yet... as unless it can offer me a huge improvement (and 50mpg isn't really) then it won't pay for itself with the number of miles I do, as I don't do many long distance trips.

How would the mild hybrid system work then? Do I simply attach the motor in place of the alternator or power steering and make it spin the driveshaft at the same RPM the engine is at? Or differently...

The engine management side I can do, as I'm very familiar with how the engine management works and I'm planning on converting it to megasquirt so I can remap it.

I suggest the prius because seeing your car, it isn't a clapped out metro or such, it is a car that is similiar in value to a Prius. I know their prices have gone back up again, have you priced one lately? I bought one of mine for $3,000, the second for $1500, and the third for $1,000. All had something wrong of course, but easily fixed, easier than adding a hybrid system to an existing car! And btw, I have built a dual-powered hybrid, by adding an electric motor to the rear wheel of a Ford Aspire (sorry can't find the pics easily), it was a LOT of work. But it did allow all-electric driving of the car, no gas at all for local driving.

Thanks for the idea :)

Well I'm actually holding out on the idea of switching cars because my uncle has offered me his Honda Civic hybrid for £900 when he comes to sell it. That could be a fair while away though...

Hybrid cars are not very common over here, certainly not for that money. Also my car is not worth as much unfortunately, if I were to sell it I might get perhaps £500 for it but not really much more... I like the idea of using it as my project car even if it costs me because I love the cars and know them inside and out, having had 3 of them. (2 diesels and this petrol).

I can get 57mpg out of my car now, which is not all that bad. If I could see 65-70 out of it I'd probably be happy, so this is my goal.

None of the smaller engines (there's 1.1, 1.4, 1.6 and 1.8 versions) offer much higher efficiency, only Rover's VVC engine which is a little like a honda vtec, offering variable valve control. Even if I fitted this I wouldn't see a huge improvement as the book states mine at 48.4mpg, and the VVC version is around 49.3.

Currently I'm wanting to try aerodynamic changes, hot air intake, higher tyre pressures and power steering delete. I'd really love to try the electric assist idea as even if it just makes a little difference it would be worth testing :).

nimble,

What you say probably makes sense from a practical view point, although, I fear your dollar estimates are a bit off.

But, where's the fun in that? Leave the dreary OEM already engineered to death stuff to boring practical folk.

We are dealing with "The Mad Technician" here who is set on satisfying his inner geek. I think most of us here have an inner geek. We just don't have the bullocks/lack of sense to act on it! Well, some of us don't. Many here have. Perhaps some day I will try something as well rather than just read of it.

I hope chris does this and ends up kicking the pants off prius numbers, which can be done with a little hypermiling thrown in.

Chris, if you do end up placing a motor/generator/starter where the PS pump used to live, will you keep the alternator?

It would be nice to lose it as well, but, would require added circuitry to maintain 12V functions. I think we have already determined that an electric motor assist should operate at a considerably higher voltage to keep the weight of such components manageable. Leaving the alternator to handle this will save you a fair bit of wiring and componentry.

As for a belt drive system having the torque capabilities to handle this duty, I don't see that being a problem. Ribbed serpentine belts in modern cars can easily power an AC compressor and all the other bits. AC compressors by themselves a fair number of hp.

Thanks :) it seems you understand my mindset here! lol.

Ok, so I'd probably want to keep the alternator yes, but I could set up a switching system to disconnect it (freely spinning it will hardly consume anything) when cruising or gliding, then reconnect under breaking, low battery voltage or on-demand when I tell it to.

If I put on a motor in place of the power steering pump which I think is the best place for it, then I suppose all I need is to stick a pulley on the end of the motor and bolt it in place. That's the easy part... now how to control it?

Forgetting the wiring, battery power and motor drivers for the minute, I can worry about those later... how should the motor actually perform its task? Should it be made to spin at the same speed the engine is trying to drive it... or slightly quicker? That's the bit I'm not too clear on...

Edit: I have seen an alternator being used as a motor before, could any alternator be converted to perform this task? There is a company near me that refurbishes and rebuilds them, they could perhaps make up one that could do the trick.

I'm all for doing mods. A Prius can get over 100mpg when modded.
I've offered an answer to chris question; the power-steering to motor assist mod it just isn't worth it the effort. Adding a 5th wheel electric drive is my suggestion, can be hidden between the two rear wheels, not ugly tacked on the back like the van pic.

Lighten up the car in a big way would net more gain than a little electric motor assist.

My opinions, do what you want with them, they were free...

There is another thread discussing this very topic where someone brought up the fact that alternators are AC motors, not DC. So, this complicates things. Turning an AC motor gets kinda complicated, especially when you want to do it with a DC power source and control the speed of it. So, I think the way to go is with a DC motor.

As for how fast to turn it, do you mean pulley ratios? I would gear it as low as possible. Figure out what rpm it is capable of and gear it so that it reaches something close to max rpm at engine redline.

I think such a system would allow you to get the considerable percentage of your power from the electric motor at cruise speed. You might even get away with leaning out your fuel/air ratio a fair bit as the motor wouldn't be working all that hard, kind of like honda does with the insight and VX under low load situations.

nimble, your 5th wheel idea sounds interesting and definitely the way to go for pushing you along at mph in a traffic jam, but, would it work at speed? I would think that there would issues with the wheel scrubbing the ground during turns. Did you use some sort of way to get it to steer with turns or do you just yank it up while cornering?

Hmm, well I had planned on making the car run lean anyway. I might need to incorporate EGR with that to offset the higher emissions though.

Ok I didn't realise that about alternators, so it would have to be a DC motor in that case then :p. I didn't mean the pulley ratios etc no, I meant in order to lighten the load on the engine does it basically just have to try and spin the engine at the same speed it was trying to go anyway? If that makes sense... So if the engine is running at 2000RPM then you make the motor attempt to spin the engine at 2000RPM. Or does it have to be slightly faster etc... basically a mechanical/physics question rather than a practical one.

Thank you for your input nimblemotors it's greatly appreciated! I understand the 5th wheel idea is probably better in the end than electric motor assist, but on my part it would probably require less mechanical work and is easiest to install and remove. I know that it won't necessarily give the same benefits as it can't drive the car on just electric but saving fuel around town isn't my main concern as most journeys are to customers houses where fuel is paid for anyway, its saving fuel on longer trips I'm interested in :).

chris, the motor will spin at the same speed as the engine, assuming the belt's not slipping. It's just a matter of trying to make it spin a little faster. and during regen braking, a little slower.

btw, i think regen can be had although someone earlier said it couldn't. it's just a matter of a somewhat more sophisticated controller. but, seeing as the electrical stuff is your specialty, i think you can do it.