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2004 Mazda RX8 with Automatic Transmission

1966 Views 8 Replies 4 Participants Last post by  elihu
Background: In 2013, my daughter and I converted a 1999 Ford Ranger Truck as a high school senior project. It was a simple conversion using 30 CALB 3.3V 120ah prismatic batteries in a tool kit in the truck bed. We bought an EV conversion kit including:
a universal adaptor kit to mount the motor to the manual transmission;
a Motenergy DC Traction Motor (ME1002);
The ME1002 is a Series Wound DC motor perfect for lite truck and small car EV conversions. Continuous current of 200 amps, and 550 amps for 2 minutes. Voltages from 48 to 144 VDC. Efficiencies of up to 92%. Perfect for use with the Curtis 1231 Motor Control. The power is 26 KW (35 HP)continuous, and 63 KW (85 HP) peak. More powerful than the NetGain Warp 9 and ADC FB1-4001 motors.
Curtis 1221C controller
Final product was a 96v 120 ah ev.

The truck worked but was'nt very efficient (heavy), and I did not spend money on a good BMS, resulting in failing battery cells after a year or two,

Fast forward:
My wife and I moved to back to Hawaii leaving the grown children in Colorado and I brought the EV parts with me (alas, the Ford Ranger got scrapped).
In December 2020, I found an RX8 with automatic transmission donor vehicle that was in good condition and inexpensive and took the bait.

I want to use the transmission to couple the motor to the drive-train because it is there and I have adjusted the universal adaptor to fit the housing and splines, etc. The ME1002 is currently bolted together in the vehicle.

I have purchased:
6 Tesla Battery Modules: 6 x 24v (22.2v?) 250ah to make a 144v 250ah system
1 Orion108 BMS
1 KDH-E - High Power Opto-Isolated Brushed DC Series/PM Controller with Regen (72V-144V) (400A-1500A) - 144V, 800A

My main concern is getting the automatic transmission to work, because it is there.
Also, is it possible to use the regen capability on this build?

I look forward to ideas, especially on the transmission.

Jeff Hart
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It's strange: there are probably more RX8's converted to EVs than the total number of RX8's I've seen on the road in my life. :D

I realize that you have the automatic, but the cost and effort of making it work well in an EV would almost certainly be greater than the cost and effort of replacing it with a manual transmission, given that manual transmissions are normal for the RX8. There are lot of variations of Mazda transmissions but generally, the transmissions of the Miata/MX-5 fit the RX8; that can be handy for supply as Miatas are much more common than RX8s.

No, regenerative braking is not practical with a series-wound motor. The Curtis controller can handle plug braking, which is not the same thing (and not desirable).

Tesla Battery Modules: 6 x 24v (22.2v?) 250ah to make a 144v 250ah system
It is unfortunate that some people who sell batteries and modules but understand nothing about them seem to think that every battery runs at some multiple of 12 volts, so they list these modules in their ads as "24 volt".

The Tesla Model S/X modules have six groups of cells in series, so their nominal voltage is six times whatever that particular cell's nominal voltage is considered to be. At 3.75 V/cell, that's 22.5 volts. Charging voltage could be as high as 4.2 V/cell (but you don't have to go that high), which is 25.2 V. There's nothing special about the 24 volt level, but it's near the top of the charging voltage range.

So the nominal pack voltage would be about 135 V, and the controller needs to be able to handle over 144 volts when the battery is fully charged.

I suggest checking the specific model of the Curtis controller, since according to one copy of the manual, the 1221C is only rated for up to 120 V (nominal) - you should confirm that either you have a higher-voltage version of the controller or that at least your highest battery voltage after charging will not trip the overvoltage shutdown feature of the controller.

Or you could go with five modules.
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Bummer on the automatic trans but I was getting nervous thinking about making it work.

I purchased a Kelly KDH-E - High Power Opto-Isolated Brushed DC Series/PM Controller with Regen (72V-144V) (400A-1500A) - 144V, 800A to go with the higher voltage of the new system.

I will check for used manual transmissions.
I purchased a Kelly KDH-E - High Power Opto-Isolated Brushed DC Series/PM Controller with Regen (72V-144V) (400A-1500A) - 144V, 800A to go with the higher voltage of the new system.
Sorry, you clearly listed that but I still had your original Curtis in mind!

The regen feature of the new controller will only work with a permanent magnet motor, not your series motor.
Do I need a Mazda transmission if I am refitting to the ME1002?
Do I need a Mazda transmission if I am refitting to the ME1002?
I'm suggesting a Mazda transmission to fit the car, not to fit the motor. You can use any transmission that fits in the space (and for which you can get or make an adapter to mount the motor and a coupler for the input shaft), but if it isn't one specifically compatible with the car you will may need to customize the shifter (to line up with the hole in the transmission tunnel) and the clutch linkage (assuming you're using a clutch) and the mount. In the case of an RX8 (and MX-5/Miata) instead of a rear mount to the car's structure it has a Power Plant Frame, which is a beam connecting the rear end of the transmission to the nose of the final drive (diff) housing.

Yes, if you have checked all of the fit considerations and can build what is required, you can use a non-Mazda transmission. Lots of people do use different transmissions than what came with the car, in both EV conversions and engine swaps. It has become bizarrely popular to swap GM V8s into Miatas, and they generally use transmissions salvaged from GM cars (Camaros) to fit the engine and to handle the torque... but they need to make custom mounts, and they change the structural design of the car.
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I am in Hawaii and concerned about availability but shipping $ is likely worth potential issues.
Hi, what is rpm range for ME1002? Do you have torque data for your setup?
I don't know of any reason why you couldn't just use the automatic transmission if you want to, unless there's some complex interaction with the ECU that you can't get around. (I'm working on an RX-8 conversion, but with a 6-speed manual. I don't know anything about the automatic version of the car.) It might be possible to swap in a manual transmission though; not sure if the body is substantially different or if you can swap parts and have it just work.

It looks like the ME1002 has a double-ended shaft, which is useful if you want to use the crankshaft position sensor thing from the original engine and mount it to the motor shaft, to fool the ECU into thinking it still has a regular engine. From what I understand, the tachometer, power steering, and ABS system won't work right unless they get some sort of canbus messages from the ECU telling them what the engine RPM is. I haven't actually gotten that far in my own project, though.
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