The New Project

1969 Mercedes Benz /8

I’ve been looking to start a new project, and I found this beauty on Craigslist. At $500, I had to at least check it out. I went with my brother and found that it was 99.9% complete. We towed it back with the Jeep, and I got started on some troubleshooting.

It wouldn’t fire, but it turned over and sputtered. After taking off the valve cover, I found that the camshaft had seized. The engine was toast. So much fir having some fun before the conversion…

AC Conversion

This conversion is going to be AC rather than DC like the MG. I will be reusing a lot of components to make a bastard of the Mercedes, but you won’t be able to tell until you look under the hood.

The Motor and Inverter

I’m using a motor out of a Nissan Leaf for this build. It has nearly twice the continuous rating of the K11 in the MG, 80kW vs 45kW. This motor has no brushes, and it could very well outlast the car around it.

I am reusing the power stage of the OEM inverter, but I have replaced the control board with another one from Paul: Nissan Leaf Inverter Control Board. I currently have the motor running with a Prius throttle pedal and some batteries from an I-Miev. Speaking of which…

Batteries

This battery pack is nearly twice as large as the one in the MG, which is reasonable for a car that is significantly heavier. At the same time, I’ll be aiming for a more comfortable and practical daily driver. No blistering burnouts for the Benz, unfortunately. Between the larger battery , regenerative breaking, and some efficiency improvements I should see significantly improved range. The battery is comprised of 88 LEV50 cells. These have a nominal voltage of 3.6v and a capacity of 50ah. The pack had eleven sets of eight and two sets or four.

Again, I got these used off of eBay, and I spent an afternoon tearing it apart and testing everything. They all tested good, and I used them to test drive the Leaf motor.

Another excellent thing about these batteries is that they include balancing boards. They are BMS slaves that will take over the critical role of keeping my batteries healthy.

Where I had to spend some significant dough to get that system in the MG, I will simply reuse these boards in the Mercedes as is with the help of a BMS master controller from Tom de Bree of DIY Electric Car Forums.

Gearbox and Adapters

For this build I will be using a transmission, though not the stock one from the Mercedes. I had an extra one that we removed from the ’66 Mustang a while back when upgrading to a T5, and it will serve perfectly in this vehicle. It’s an old school 3 speed from the same time period as the Mercedes. I will leave it in second gear to get a final drive ratio of 6.825:1. I’d like a little closer to 7 or 8:1, but this will be fine. An adapter plate will bolt to the front of the motor, which will then bolt to another adapter plate on the transmission. I have created some CAD drawings for the shaft coupler and adapter plate that I will upload later.

Charger

I have settled on a 3.3kW Lear charger from a Chevy Volt. Tom’s added that functionality to his board for me using the information already out there about the CAN protocol that it uses. It’s liquid cooled, so I’ll add it to the cooling loop for the Nissan Leaf motor and Inverter. It’s more powerful than the charger in the MG, so I’ll still charge the larger battery pack in a similar time on my recently installed level 2 charger.

Fun times ahead!

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5 thoughts on “The New Project”

  1. Wow!! This is just like what I want to do. I had no idea all this was going on. I just pictured the motor in your shop, sitting there, and little crickets chirping quietly in the background.

    1. Haha, I feel like there are crickets right now… I need to get the motor our of the Mercedes so I can get it out of my garage!

  2. I’m inspired by this use of the FWD Leaf motor in a RWD car. Can you tell me more about the Leaf motor mounting and how you are hooked up to the 3 speed gearbox. I have a little 1957 Austin that I would like to do something similar.

    1. Thanks! I made an adapter plate that bolts to the front of the Leaf motor. I traced a CAD drawing someone else provided to get the bolt hole and locating dowel locations and the general shape. It still needs some work – I need to add a locating ring, which I will do if I have another one milled for some reason. From that plate, it bolts to a CanEV adapter plate for a T5 transmission. I made a coupler using a sort of large rod I drew with the appropriate clutch centers pressed and welded into each end. I have more info and pictures in other posts, including the drawings I used to make the plate and coupler. If I were to do this again, I would probably use an EM61 motor for a 2012 and earlier leaf. It is separate from the inverter, which makes the packaging a lot easier. You could practically fit most of the motor directly in the transmission tunnel, leaving more room for other stuff. I would also like to have a smaller adapter plate setup to mount directory to the transmission and skip the large bell housing, but that’s just wish listing at this point!

  3. Super cool stuff. I’d love to convert an old COE (cab over engine) truck to full EV. Might even add fake exhaust and augment sound just to throw everyone off.

How about that, eh? What do you think?