Build Your Own Electric Car!

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Introduction: Build Your Own Electric Car!

About: Ordinary guy with no special skills, just trying to change the world one backyard invention at a time. See more at: http://300mpg.org/ On Twitter - @300MPGBen and at Ecoprojecteer.net

(AUTHORS NOTE, July 9, 2017)
Hi Everyone, there' been a lot of views on this project lately! Thanks for coming by to read through it! Much has changed since I originally built this car, including the fact that there are a LOT of great commercially built electric cars available for sale, including used at good prices. When I built this car, pretty much the only electric car available was the $100,000 Tesla Roadster. Now, I'm driving a used Mitsubishi iMiEV electric car and power it with my Solar Garage! Please take a look at my other Instructables and at 300MPG.org for the latest on my clean transportation adventures!)

The "Electro-Metro" Project.

Can't afford a Nissan Leaf? No Problem!

Build a cheap electric car yourself by removing the the car engine, replacing it with a forklift motor, and adding batteries.

I have plenty of videos about this project at:
http://www.youtube.com/user/BenjaminNelson
and 300MPG.org

The primary "build blog" for this project is at:
http://ecomodder.com/forum/showthread.php/ben-nelsons-electro-metro-build-thread-848.html
but watch out! That is a good read for when you have WAY too much time on your hands.

For a good intro to basic electric car construction, stick with this Instructable. (If you are more interested in electric MOTORCYCLES, please see this intractable: https://www.instructables.com/id/Build-Your-Own-ELECTRIC-MOTORCYCLE/


For more in-depth construction information, check out the instructional Video DVD available at 300MPG.org
I have now also converted that original DVD to a series of YouTube videos. See them in THIS playlist:
https://www.youtube.com/playlist?list=PLmHss3DBZUilepzTmr-XAVwpRRCqMv7Ny

Step 1: Get a Car.

The first thing you need to do is get a car. They are not all equal.

I was looking for something lightweight, with no power anything.

Heavier cars need more energy to push down the road, thus limiting your range on batteries.

Things like power steering and power brakes run off the engine, which is going to be removed anyways, rendering them useless. Power windows and locks add weight and complexity to the vehicle.

I ended up finding a Geo Metro for sale, for $500. The engine ran fine, and the body wasn't too bad, but I couldn't drive it home because the clutch was messed up. Oh well, this conversion isn't going to use a clutch anyways!

Make sure the car doesn't have anything major wrong with it (other than maybe a blown engine!) You want to do a Conversion, not a Restoration!

Step 2: Remove Anything Gasoline Related

Remove anything related to the gasoline internal combustion system.

That means that you are going to take off:
Gas tank
Exhaust, muffler, cat
Engine
Starter
Radiator
Coolant tank
Fuel lines and filter

and anything else you can think of.

Removing all the extra bits saves weight and cleans up the car, making it easier to paint, run wiring, and do everything else in the conversion.

If you remove parts carefully, you can sell them to help cover the cost of the conversion. I bought the car for $500, but then sold the engine, gas tank, and radiator for $550. Free car to convert!

Make sure to not alter any safety gear. In this case, I was careful to make sure the driver and passenger airbags remain intact and functioning.

Here I am removing the gas tank. I had never removed a gas tank before, and couldn't figure a good way to drain it. What a mess!


Here's a video of me literally lifting out the engine with a pulley and clothes line! Hard to answer my phone with my hands full like that!

Step 3: Adapter Plate

You did make sure to keep the transmission, right?

We will use the car's original transmission as a way to connect power from the electric motor to the car's wheels.

The trick here is how to attach the motor to the transmission?

We will make an "adapter plate" out of a chunk of plate aluminum which has holes in it to line up with both the transmission and the end of the motor.

I pulled the transmission out of the car, and flopped it on some tagboard, then outlined it in pencil and marked all the holes.

I then took that and the motor end cap to a local machinist who is also a hot-rodder and knows way more about cars than I do.

He cut an aluminum plate to the size and shape required, complete with carefully aligned holes. The center of the motor drive shaft and the center of the transmission driven shaft need to line up perfectly.

Before bolting the motor and transmission together with the adapter plate, we need to design a coupler that will mechanically connect both drive-shafts.



Step 4: Coupler

The coupler is a means of connecting the rotary power of the electric motor to the transmission to power the car.

While there are a number of ways to do this, including keeping the clutch and machining the flywheel, I chose to keep it simple and use a "Lovejoy"-style connector.

Lovejoy connectors have three fingers and a shaft-hole. Put one connector on either shaft, and a rubber "spider" between the two. Poof! you have a mechanical connection!

Lovejoy couplers are designed with a keyway and set-screw, but both the shafts on this project are splined! Splines are much stronger than keys, but much more difficult to machine!

For the transmission, I took the old (broken) clutch plate and ground off the rivets to get just the middle splined center out. The machinist cut off the ears, lathed a step in the Lovejoy coupler, pushed the clutch spline in there, and welded it in place.

The motor spline COULD have been more of a challenge, as I didn't have any part with a spline on it for the shaft to go to. Fortunately, the motor was double-shafted (one on each end) and the back end went to a drum brake, which was the parking brake on the forklift.

I took the drum brake apart, sure enough, it was the same spines on the back end. I was able to get the very center, splined section, of the brake out, and use it to make the motor half of the coupler.

Line up the motor and transmission, with the coupler halves between them (with the spider in there) and bolt both the the adapter plate.

Congratulations! You have an electric car drivetrain!!!




EDIT!:

I ran the car all summer with this set-up, but a few weeks back, it failed. I don't think the issue was the style of coupler. I think the main issue was that I installed the transmission and motor in the car seperate from each other. Because of that, I never got a true center alignment and bench test.

I rebuilt the coupler (with a little help from some friends - OK, I would have been lost without them..) by welding both female splines to a piece of flat steel plate, rounding it off, and adding a tubular jacket.

Then, the new coupler, motor, and transmission were all mounted to each other, tested, centered, and tightened. THEN the whole thing got put it the car.

Been working great since then.

Watch the video - it will make sense.




The first three photos at the bottom are the original "Lovejoy" coupler. The last two photos are of the current one-piece "solid" coupler.

Step 5: Motor

What's an electric car without a big electric motor to run it!?

I bought my motor for $50 out of some guy's garage. He had bought a junky forklift to build his own automotive lift, and had no use the the motor and some other parts.

The motor was very rusty and greasy, but it did spin (not fast or easily) when I applied 12 volts to it.

Rebuilding an electric motor is very easy. There are only a handful of parts to it.
I degreased it, removed the coils and sprayed them with insulating epoxy, checked the bearings, put it back together, and painted it.

I also had the machinist put the rotor on his lathe and take a tiny bit off the commutator. That makes it looks new, and provides a smooth, conductive surface for the brushes to ride on.

I also replaced the brushes, purchasing new ones at a shop that specializes in forklift motors. $50 for the new brushes brings the total cost of $100 for a pretty decent electric motor.


Step 6: Batteries

The motor won't do you any good, unless you have some batteries to power it with.

This car uses 6 x 12V batteries, for a 72V system.

These are Deka Dominator true Gel-Cell batteries. They can not leak or spill acid, nor do they require watering.

I was fortunate enough to be able to get these batteries, slightly used, for $12 each - essentially scrap metal prices!

One downside of these batteries is that they are picky about charging voltage. I was finally able to find a 72V charger designed for these batteries, and got it used for $200.

If I had used the more typical deep-cycle flooded batteries, I could have used a different charger, or even 6 12V chargers, one on each battery.

Four batteries are in the cargo compartment of the car, and two are in front, where the radiator used to be.

For the rear batteries, I cut two pieces of bed frame to lay across the spare tire well, and ran a bolt through the end of each piece down into the frame of the car.

For the front batteries, a few friends came over and helped me weld in a metal tray for the two batteries to sit on. Then I cut two short pieces of unistrut, and ran threaded rod through holes in the tray to bolt the batteries down. I then insulated the front batteries with rigid styrofoam and re-installed the front bumper.

I went to the boat store and bought a "battery charger power inlet". This is a male electrical connection with a rubber cover. Since the gas tank was already removed, I installed the power inlet where the gasoline used to go in.

I added an additional circuit in my garage, just for the car, and have a 25' 12 gauge yellow extension cord with power indicator light in the end, just for plugging the car in with.

Plug it in at night, and it's charged the next morning, automatically.



Update! I later played around with more batteries. With a motor controller that supports higher voltage, I was able to run up to 144V (12x 12V batteries.) At that voltage, the top speed of the car was at least 73 mph, but I really had no cargo space.
Just so you know, Ford Ranger front coil springs fit the back of a Geo Metro, but you have to shorten them.

Step 7: Controller

The controller is an important part of the electric car conversion.

The controller is a solid-state electronic box that controls the power (speed) between the batteries and the motor.

My controller is a Curtis 400 amp peak PWM controller designed for use with series-wound motors. It can run on 48-72 volts.

The higher amperage your controller is, the better your acceleration will be. The higher voltage, the better top speed and efficiency of the car.

Also, keep in mind that amperage is also what defines range in a battery. Capacity is marked in Amp Hours, but draining a battery at double the amps will give you LESS than half the run time! Having a controller running higher voltage will use LESS amps to do the same amount of work.

What's this mean? Buy the highest voltage controller you can afford! 48 volt controllers are cheap, as they are used in so many golf carts. 100V+ controllers get expensive real fast.

My 72V controller seemed to be a good compromise of cost and efficiency. I bought it slightly used on E-Bay for $300.

Follow the schematics available through the controller manufacturer to connect the batteries to the controller and motor with heavy gauge cabling, such as welding cable, with solid, heavy-duty lug terminals on the end.

The controller requires a 0-5Kohm potentiometer as a "throttle". This could be as simple as a $3 Radio Shack part, or as fancy as a purchased, specialty part such as a Curtis PB-6

I split the difference and installed a 0-5K pot inside a free-from-the-junkyard forklift throttle control.

Run the gas pedal cable to the potentiometer, so that when your foot is on the gas, it sends a variable signal to the controller.


Update! I later switched over to running an Open ReVolt motor controller. It's the same one you can find here on Instructables at https://www.instructables.com/id/Homemade-100-HP-Motor-Controller-for-an-Electric-C/
That controller is good for up to 144V and 500amps.

Step 8: Other

Currently, the car is insured and registered, although the DMV is still requiring that I drag it in and PROVE that there is no engine in the car before they give me the emissions tesing exemption.

This car can go for 20 miles on a charge, and has a top speed of 45 MPH, the speed limit right outside my house. In town is all 25 mph anyways. My typical ride is 10 miles for going to work, grocery store, post office, etc, and back home.

If I doubled up the battery pack, I should be able to go 30 to 40 miles on a charge.

This project has cost me about $1200 total, including buying the car in the first place. If I would have done the machining myself, I would have only spent around $800 for everything. This car charges at my house through a renewable energy program. All electricity comes from wind, bio-gas, and other renewable energy sources.

I kept the back seat and can carry four people total.

The original driver and passenger airbags are completely intact and functional.

I mostly drive this car in third gear. Turn the car on - put it in third - drive. It's really that easy. There's no engine to kill, so you don't have to push in the clutch before coming to a stop. The motor has so much torque that I can pull away from a dead stop in fourth gear.

I still need to come up with a heater. (EDIT: Please see below) I think I will wear an extra thick coat and gloves for winter driving and have an electric defroster on the dashboard to keep it from frosting. The heat issue has been on my mind since the start of this project. The inefficiency of a gasoline engine is a blessing in a cold Wisconsin winter.

I did gloss over a few steps of this project.
I skipped telling you how many times I took apart, and put back together, the electric motor. How many times I lugged it back and forth to the machinist's. A friend and I were up til 2 in the morning one night fixing the control arm mount! Or how I had to literally shorten the motor because it was too long to fit in the car! But those things are for another story at another time!

I made sure to have an interlock, so I can't accidently drive away while plugged in. Make sure to have a nice big fuse inline of your main battery pack.

All the little challenges of a conversion like this are part of what makes it fun and interesting. In my case, I did a fair bit of experimenting of the best way to run the power brakes.




Winter Heat:
Sure, gasoline engines aren't efficient, but all that waste heat sure is nice in the winter. Since this car no longer has the original engine, it doesn't have the original heat either. The blower motor is still there and works fine for defogging the windshield.
Some EV converters remove the original heater core and replace it with a ceramic heating element that runs on their pack voltage. That sounded like a lot of work, and I was already sick of tearing apart the dashboard.

I already had a household (120V AC) electric oil-filled radiator. I just put that behind the passenger seat, and run an extension cord out the window to a timer.
The heat comes on automatically in the morning and heats up the inside of the entire car before I get in it.
The mass of the oil in the radiator stays hot for about 10 minutes or so after I leave. Most of my trips aren't any longer than that anyways.

I like that with this heat system in that:
1) I didn't have to buy a darn thing
2) The entire interior of the car is already warm - seats, steering wheel, everything!
3) This also helps keep the batteries warm.
4) All the electric power comes from the wall, instead of the batteries

The only down side is that if I am parked all day somewhere that I can't plug in, I don't have that same heat for the ride home. On the other hand, most of my trips are pretty short, so it's not the end of the world.

This heat system consumes about 5 cents worth of electricity per use.

BRAKES:
One of the reasons why I chose this car to convert was that it has manual windows, manual locks, manual transmission, non-powered steering,pretty much manual everything - except the brakes. The first time I drove the car as an electric conversion, I found the brakes to be a little hard. (You CAN stop the car WITHOUT power brakes, you just have to push really hard!) It was just a low-speed test drive, but it was pretty obvious that I had to work on the brake system. Power brakes work on vacuum created by the engine. Without an engine to make the vacuum, the brakes just don't work the way they should. 
Some people say to find a different, manual, master brake cylinder and install that, or even just to punch a hole in a certain spot in the cylinder to convert it to manual. Neither of these sounded like great options. Really, I just needed an electric way to make a vacuum.
So, to start out with, I played around with an aquarium air pump, just to learn how the vacuum brake system works. After that, I starting looking around for a 12v air pump with a connection on the "In" end, so that it could be used as a vacuum pump. A friend of mine dug one up, along with an aluminum bottle that had a threaded connector already on it.
I connected the air pump to 12V+ power through a vacuum switch. The vacuum switch measures vacuum in the bottle - if there isn't enough vacuum, the switch turns on the pump.

Now the car has power brakes, just like it did originally, only it's driven by a tiny electric motor in a little pump, instead of by a gasoline engine. Compare this to newer versions of the Prius, where the air conditioning is driven by an electric motor. That way, you can have AC without the engine running!

Step 9: Now You Make One!

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717 Discussions

Please can you expantiate on the adapter plate part.
I'm thinking of using one of those beetles. But haven't got one yet
I wanna outline my plan and cost before plunging.

1 more answer

This might be a dumb question but can you change gears? Like I understand starting it in third to get an average gear ratio but say someone did this with a truck? Just wondering as I'm trying to go unique with my business I'm also working on a remote control riding mower or something of the like rather electric than current gas model be glad to have any help lol

1 more answer

Yes, I can change gears. It's slightly slower than with a clutch, but works just fine.
I always tended to not shift much in this car. In town, I could just leave it in one gear if I wanted.

I am interesting about solving ASP, EPS; ABS and ECU ? Just remove it all, or keep some of it somwhow? Thanks!

1 reply

I don't know what half those acronyms are! Converting a little bit older car simplifies things as they were less computer-based.
On my car I did see that there is a dedicated air-bag computer which is separate from any engine computer. I made sure to leave the air-bags and air-bag computer untouched, so that the car would still have its original safety features.
I would remove any unnecessary computers related to the engine, fuel tank, etc., but make sure to leave anything safety-related, such as anti-lock brake controls.

Hi instead of using aquarium pump you can by vacuum pump from audi a4 or jetta 1.8 turbo engine good luck with your project

I had to look up what an 1800S was. Cool Car! As I write this (January 2018) there are plenty of great electric cars out there a person can buy used at a good price. One great reason to still convert a car is if it is something not available as an electric, such as an old sports car, a convertible, or at this point, even just a pickup truck. (EV pickups are great, and I'm shocked that we still don't have a mainstream manufacturer of electric trucks!) Take a look at EVAlbum.com for inspiration or try contacting a local chapter of the Electric Auto Association to see if you can find somebody nearby to work with!

Iv had an idea for a while now but never had an electric car to test it but maybe someone on hear might. Im an aircraft tech and on some aircraft there is what we call a R.A.T. its an emergency generator that pops out and is powered by a prop, (works like a windmill). Iv allways wondered if the same idea could be use on an electric car. Maybe have a couple altenators driven by props and some kind of air inlet to feed air to the props. Not sure how to convert alts to higher voltage but im sure somebody could figure it out and yrs it would only charge at speed but your not using juice sitting still either.

1 reply

The props would add drag and it will end up using more energy then it can put back in to the battery.

0
user
Isack8

9 months ago

can this be done to an automatic transmission?

A question???

Really love your electric conversion post. I was kind of curious and want to ask a question. I really love automatic transmission but its very complicated mechanism, and electric cars solve the problem quite well. Just dont have transmission... it is so cool. But there are no electric cars with reasonable milage... so... Could something like that happen? A regular combustion engine (serves like a battery) connected to a electric generator, next connected to a electric motor and wheels. No direct connection between engine and wheels -> no stalling or uncomfortable changing gears. Just an electric motor charged by combustion engine. Something tells me that in that way, the vehicle can use smaller engine (less polution and less money). And every system will work.

1 reply

This is exactly how the Chevy volt works

0
user
farna

1 year ago

Cheapest way to add range is to install a small generator -- even a little 700W (running, 900W peak), $99 Harbor Freight unit would add a LOT of cruising miles. It would sip gas, so you'd get 70+ mpg, and could even use fewer batteries for less weight. The 20 mile range car would get triple the range, as the batteries would mostly be used for taking off, cruising would run mainly on the generator. Would take some work on the control side though. Should be able to rig the generator basically as a battery charger and run it all the time, that would be the simplest way. It would only run at higher speeds when there was a lot of current draw. Just make sure the generator exhaust is run out of the car... sort of goes without saying! Makes it a hybrid instead of true electric, but would be more practical. The generator could provide all cruising electricity. Ideally you'd want a little more generator than required for cruising so the batteries would get a little extra charge for when you get back in town.

5 replies

At 100 Kmph my Nissan Leaf (one of the most aerodynamic cars on the road) draws about 15000 watts of power, that is getting to be a pretty good sized gen set.

That's a lot more than I thought it would be! Anything over a 5K generator would be rather large, 2500-3000W would be a better physical size. So you could add some miles, but not quite enough to cruise on... unless you built something like a trailer with a large generator on it. Would be good for long range running, and would be a bit more efficient than a typical gasoline car, but you may as well just rent a small car when you need to make a long trip, assuming your normal commute is short enough for an electric car (or hybrid with a small generator). Might double range with a small generator, but more than likely not add more than 20-30% -- depends on a lot of variables. May as well add 2-3 more batteries for the space and weight of the generator...

My thought was to take a more direct approach and use a small 10HP diesel engine driving a single wheel behind the car. Put the whole assembly on a receiver hitch so it can be removed and put on for the 4 highway trips per year that I take. This would eliminate all the inefficiency losses due to running a generator and converting the power in the battery charger. The drive could be direct through a chain with a clutch to engage/disengage the drive once highway speed is reached. The electronics in the car would simply perceive the entire trip as being downhill or with a very strong tailwind!

Hmm... interesting, but more complicated. Generator just requires an electric cord connection. A mechanical engine as you describe would basically be one speed. You would still need a clutch connection (maybe electric, like a riding lawn mower blade clutch) and some kind of throttle. Otherwise the electric motor would be "helping" the engine at times. Maybe a one-way clutch so the engine never put a drag on the electric motor? Still think that would be a lot more complicated and harder to implement than a generator. Easiest thing to do is just rent a car for longer trips. Would be cheaper in the long run! I had a friend who didn't own a car, just his bicycle and public transportation. Rented a car 4-5 times a year for longer trips, even a weekend for Christmas shopping. No car insurance or maintenance, nor of course payments, just $1000 or so a year in rental fees. Would work with an electric car for commuting if it has the range.

Been there, done that, wrote the Instructable on it. https://www.instructables.com/id/DIY-Plug-In-Hybrid-Car/
I
t worked fine, but the main drawbacks were how much cargo space got used up, and the noise from the generator. Generator exhaust was routed through the bottom of the cargo area and through a riding lawn mower muffler!