# Planning 1974 MG Midget Conversion



## drKorf (Aug 31, 2012)

I just purchased a 1974 MG Midget without an engine for an EV project. This will be for short range commuting. I already have other cars for longer distances (Honda Insight), hauling cargo (Mazda B2300), and the track (BMW 325). I generally drive less than 10 miles per day at 45 mph or less. But I would like the capability of 20-30 miles and 80 mph.

I know almost nothing about electric vehicles. All advice is welcome.

I have done some motorcycle and car work. A friend of mine is a mechanic who owns a garage (where we are currently preparing a 24hr of LeMons car). I can do some welding and have access to a welding shop with a variety of welders and cutters.


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## Ziggythewiz (May 16, 2010)

Welcome! Be sure to read up in the Wiki to get the basics, and start building a plan. Since you know most of your performance requirements, the next big thing is to establish the budget. Let us know when you have specific questions.


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## drKorf (Aug 31, 2012)

Wow, batteries aren't cheap. A petrol engine will use around 100 gallons per year for my purposes. So, something like $2000 over a 4 year period (assuming $5 per gallon), or $6000 over a 10 year period. If lead acid batteries are replaced every 4 years and lithium ions are replaced every 10 years, then I'm seeing that batteries alone could cost something similar to gas. I wonder if the price of batteries is expected to improve in the near future.


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## Ziggythewiz (May 16, 2010)

Yes, battery prices will come down, but how much and how soon is anybody's guess. As for gas prices, if you could secure 10 years of gas at today's price you'd be a very lucky man.


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## fb_bf (Jul 6, 2011)

I'm about to hit my 1 year anniversary for my Mg Midget conversion. I drive it daily, and it has worked out great. Midgets do make good EV conversion cars. My car averages about 200 to 210 wh/m driving around town and at 50 mph. I have driven it 112 miles on one charge. This is when the BMS said my cells were dropping below 2.7 volts. I have 38 160Ah cells in it and it weighs about 170 lbs overstock. I have driven a midget all my life (37 years). I sold my gas one last February when I was sure this one would fit the bill. If you have any questions please ask. Mine has the original clutch, which I highly recommend if you want the car to drive like an original. I'm sure that most people who see my car don't even know it's electric. You can check out the site I put together on it. I'll have to get around to updating it. I'm just a couple of hundred miles away from 4,000.


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## drKorf (Aug 31, 2012)

I've seen your site and it was one of my inspirations for buying the car in the first place. I have been juggling several ideas around such as a motorcycle engine and/or turn it into a LeMons race car. But having just built and raced a LeMons car for the first time (car/boat #777 at Thunderhill 2012) I don't think I want to put that much effort into a car that drives only on the track. So electric is still the plan. I think I want to start out with a minimal number of batteries and then upgrade later on. If I have a small bank of SLA batteries, can I simply swap out for Li-ion (or whatever) at a later date?


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## Ziggythewiz (May 16, 2010)

You can swap to lithium if the charger can handle it and you already have an AH counter, otherwise you'd add those to the price of lithium.


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## fb_bf (Jul 6, 2011)

My first advice with converting to electric is to either use the warp 9 impulse motor, or something as small. The reason is that the Bemf constant or torque constant of smaller motors means that with a lower voltage battery pack you can still push a reasonable amount of amps through the motor. If you want to be able to have the car still accelerate past 3000 rpm you have to be careful about picking your motor. Certainly you can put a larger motor in and use your controller to limit the amps giving you a more even torque through the RPM range, or you can just get used to high torque for a limited rpm range. Since I've always driven a Midget, having the same torque as gas with 500 amps was just fine for me. The other recommendation for your idea of buying a limited amount of Li-on cells would be to pick a voltage target like 120 volts, and buy the 90AH cells to get there. That way you can see the performance of the car first hand. If you like it, and want to extend the range then you buy another 38 cells and parallel the new cells with the old. You'll double the range, but you won't have to change the charger, controller, and possibly the BMS. The weight will increase, but if you've planned ahead for the extra cells, you'll have the space. If you try using a lower voltage first, then you'll find yourself having to change many of the components you started with. From my experience, 10 Kwh worth of batteries will get you 40 miles range to 80%DOD, and 50 miles in limp home mode. Make sure you keep the clutch. Driving a sports car and not shifting isn't right, it just isn't. Good luck and please feel free to ask questions. I and many others on the forum will be happy to help.


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## TEV (Nov 25, 2011)

Peoples are stating here that with an electric motor you can change gears without clutch, you can search for clutch vs clutchless or something like that. Going clutchless will save time and money, retaining the clutch is nice.


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## fb_bf (Jul 6, 2011)

I feel strongly about retaining a clutch, but it comes with the design of my car. I was lucky to buy it with the Warp 9 Impulse already in it. That motor doesn't have the huge torque that is often found in the larger electric motors. I can still get fun acceleration without pushing 1000 amps through the motor because I have the clutch. My cells are 160Ah, so I only exceed their 3C rating by 60 amps and that rarely happens. If I had a 1000 amp controller and drove around in 3rd gear I'd be pushing the cells more often. I wanted a Midget that drove like the gas one I've owned for 35 years, and I have it. Without a clutch I wouldn't get that.
I know that it simplifies things to leave the clutch out, but after seeing all of these amazing builds on this site I have to wonder how much simpler the build really was because of leaving a clutch out. To me it just make the car more enjoyable to drive, and I don't think it adds that much more to a build after considering all of the other things that had to be modified to make a car electric. It is just my opinion, and I don't think anything less of someones EV conversion. Any conversion is an accomplishment that the builder should be very proud of.


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## TEV (Nov 25, 2011)

I was only saying that you can change gears all most normally without a clutch , Also if you do a clutchless connection you will have more room for the motor.


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## onegreenev (May 18, 2012)

With the MG I would not go without a clutch. It makes installation easier and you have a way to shift properly. Also DO NOT use lead acid in the tiny car. I originally purchased that Midget Frank has now and it came with LEAD and it was WAY WAY TOO heavy. Don't expect 4 years from lead acid batteries unless you don't drive it. Even then they may not last 4 years. Get Lithium and if you can get the new CALB Gray cells. Plenty of bang for your buck and you still keep your car light weight.


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