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Discussion Starter · #1 ·
Hello, My name is Philip and this website has already helped me answer a few questions. I intend to document my EV conversion here, and hope to get pointers and suggestions.

My background is sailing and I have lived aboard my sailboat for the past 11 years and did all my own engine work. My largest engine project was changing the damper plate between my Isuzu 6BD1 diesel engine and Borg Warner Velvet Drive.

I have selected a car produced here in SE Asia for my first conversion that weighs 850 kg (1870 lbs). It is a small hatchback and I hope to fit batteries under the rear seat. The gasoline version is equipped with a 1.0 liter engine that produces 67hp (50kw) at 6000 RPM and a torque of 91 Nm.

I have initially selected a 15kw AC motor that weighs in at 60kg (132lbs) and produces 150 Nm and has a rated speed of 4500 RPM. Motor drawing attached. The controller receives 96 VDC from the battery bank and I may first build one with a very limited range and a scalable battery bank. Each battery stores 20aH at 96 volts and I have estimated 2 batteries and 40aH will give a range of about 32 km without AC. Up to 4 of these batteries will be in the bank depending on range I want to achieve. Once past 4 batteries, if I need that range, my option is an integrated battery pack with 140aH.

Thank you for everyone that posted pictures and details of connecting the motor to an existing transmission. That is my number one concern. Here in are my first questions.

#1 - I have the option of selecting an exisitng vehicle with a manual 5 speed or with an automatic transmission. I gather if I go the route of the 5 speed the integration of the clutch plate is more difficult. Eventually I will want to create a mounting plate and couplings for both types of transmissions available for this car. Is it easier to do my first conversion using the automatic transmission?

#2 - Does the motor size, 15kW seem reasonable for a small vehicle like this weighing 850 kg? I do not anticipate needing speed over 70 km/hr.

#3 - Does a range or 32 km sound reasonable for a 40aH battery bank?

#4 - The supplier is offering something described as "gearbox ratio 6.5-1 for an extra $370. I am not exactly sure what that is. If I couple to an existing transmission do I need this?

#5 - It is very hot here in SE Asia and I will need to have AC. There is no rear takeoff on this motor and so I am thinking of adding a small 2 hp 12volt motor to drive the existing Sanden compressor. SD7B10. To power the AC and 2hp motor I intend to have a 12V conventional battery too. That battery will be charged by the 96v to 12v DC to DC converter. I am thinking I need a battery charge controller between these two batteries. Again does this sound reasonable? Do I need a variable speed controller for this air con motor speed? Does this have some sort of dial on the interior of the car?

#6 The motor supplier is offering something they simply call "Vacuum Pump Brake" for an extra $125 USD. I have no idea if I need that or how this is different than the vehicles exisitng brake.

#7 The vehicle brochure says the power steering is electric. So I gather it is not engine driven.

Thank you so much in advance for any questions you can help me with.



187 Posts
Hello! Welcome to the forum!
That sounds like a good motor. Because of the light weight and your low speeds, not much power is necessary.
1. A manual transmission is much better for a conversion, since it does not need the motor to idle or a fancy controller. A clutch plate is not necessary; some builders have mounted the original flywheel onto the motor, and others make a coupler and take out the clutch.
2. 15Kw should be enough. My car uses about 16Kw when driving at 70 mph / 110kph, so that should be a good continuous rating. Usually a motor can output 2 to 3 times its rated power for short periods of time - such as acceleration.
3. 40Ah times 96V = 3.84KWh. Generally, an EV can achieve about 300 watt-hours per mile, or 180 watt-hours per Km. So with a 40Ah battery you may achieve 20 kms.
4. That is unnecessary if you couple to the existing transmission.
5. That's a good way to do AC; it will harm your range quite a bit but if it's necessary then just do it. You can try setting up a dial of some sort to change the speed, but running it at the idle speed of the original motor should be enough. No charge controller is needed for the DC to DC converter as long as the converter is current limited (most are).
6. A vehicle with power brakes uses a vacuum to make the pedal easier to press; if the car does not have power brakes you do not need it. It is just a power assist system.
7. Great. Electric power steering is much easier to deal with. You may need to send the power steering pump some signals to make it turn on.

Good luck with your conversion!

3 Posts
Discussion Starter · #4 ·
Isaac Thank you for the feedback.

The controller I am buying is actually a bit more expensive than the motor. Therefore, I suspect I am getting an "expensive" controller. Further I am going to buy the programming unit so I can program my controller.

I suspected the "gearbox ratio 6.5-1 for an extra $370 " was not necessary, Yesterday the vendor for supplied me a photo and now I can see it assembled.
Technology Cable Electronics Auto part Electronic device

The only advantage of keeping the transmission I can now see is saving the cost of the new gearbox and if the car will do a lot of highway driving. At the motor rated speed of 4500 RPM the car will be traveling at 77 km/h (47 mph) which is fine for city traffic. There are only a few highways here in this country. At maximum7000 RPM speed is 120 km/h (73 mph) which is plenty fast for a short term. In fact I worry at bumping up against words maximum RPM so would use the controller to limit motor speed to go no faster than 55mph. (5520 RPM)

This being my first build, simplicity is my goal versus cost.

The cost for the two axles in the photo is just $130. I concluded it will be easier to just buy them, cut the ends off and connect to the existing axles. This is the type of minor modification I trust local machine shops to be able to handle. I don't trust them making something that requires making a spline.

New questions:

#1 - While hunting for details about the front axle for this car I came across a website selling what they term as a "super chassis". Stabilizer? .

Vehicle Auto part Car Suspension part

I find this kind of worrying. If someone thought the current vehicle is built so flimsy that they could sell aftermarket braces to stiffen the adding the stiffener for an EV conversion a good idea? Note: I also admit I don't know exactly what this stiffener is connected too. After I remove the engine and the transmission will the current stiffener still have connection points?

Question #2 Now I think my engineering difficulty is how to mount and support the motor. Without the transmission to hang onto I gather I have to support the motor from the original engine support mounts. This will be the new fun.

Does anyone show examples of EV conversion where they eliminated the transmission on a front wheel drive car? What did the motor supports look like.

Quesetion #3 - I realized today one problem with the 96 DC to 12 DC converter. Since I intend to charge the existing 12V battery that runs the air conditioning motor using this converter I need to know the output voltage. If it is not closer to 13.6V then I will need to install an intermediate device that has a battery charging profile.
Surely, I am not the only one thinking of keeping the 12volt battery and need to charge it. My larger question is will a 2hp 12volt DC motor be overkill to run the AC compressor. I guess I will find out by trial and error.

3 Posts
Discussion Starter · #5 ·
Which car is it?
I have not purchased the car yet. Cars here in SE Asia tend to be locally made by manufacturers with names I never heard of before I moved out here. The initial car I selected costs just over $10,000 new, hence the total conversion costs need to be kept extremely low. On my first conversion I plan to exceed the feasible cost figure, however, I think I have to do that owing to one time learning curve costs. For example long term I think reuse of the existing transmission is going to be cheaper. Alternately I might be able to get the supplier to provide me the correct axles to fit the car of my choice.
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