# Planning an EV conversion on a 76 Mercedes 300D.



## foci (Jul 17, 2019)

First question from me is what to do about the trans? should I leave it or go for a single gear or is there a way to attach the motor directly to the drive shaft. though I doubt that.


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## brian_ (Feb 7, 2017)

foci said:


> I have done a lot of work on internal combustion engine swops but new to EV. any help would be grateful. I will try and answer as many questions as I can. And I will be asking a lot. I am still in concept so almost everything is a variable.


And so you need to narrow things down... a lot. The way to start is to establish what you want, in terms of performance (acceleration, speed, range), technical characteristics (what do you want to keep of the original car? is there any particular design feature you want to try or to avoid?), and constraints (budget, time to build, complexity, skills and tools required).



foci said:


> First question from me is what to do about the trans? should I leave it or go for a single gear or is there a way to attach the motor directly to the drive shaft. though I doubt that.


I don't think that's the first thing to consider. If you have already made a bunch of decisions (such as the type of motor, or where is located) then it would help to list those, since (in combination with all of the factors mentioned above) they limit and control your choices.

But yes, you can attach a propeller shaft (driveshaft) to a motor. For instance...
Duncan's Dubious Device
Motors have various shaft styles, and so would require various bits of hardware to make the connection, some of which would not be trivial.


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## scotttherobot (Mar 31, 2018)

I'm very excited to see a Mercedes EV project. They are so few and far between. I have owned and loved a number of W123 300Ds and one of these days I plan to do an EV conversion myself to one.

1976 was the last year of the W115 and the first year of the W123, depending on your market. Which have you got? 

Check out Jefferson Black's 1969 W115 300D EV. He has a blog and a series of YouTube videos on his conversion. He used a Nissan Leaf motor and a '66 Mustang transmission locked into a second gear. Good stuff. He has a forum thread here: https://www.diyelectriccar.com/forums/showthread.php?t=199135


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## lawrencerhodes (Mar 31, 2008)

foci said:


> I have done a lot of work on internal combustion engine swops but new to EV. any help would be grateful. I will try and answer as many questions as I can. And I will be asking a lot. I am still in concept so almost everything is a variable.



First of all the selection of this Mercedes is better than the W123 by 400 pounds. That being said there are some things you can do to lower the weight. You could put a Nissan Leaf drive train in the rear of the vehicle thus eliminating all the cumbersome and weighty Mercedes gear. Weight is your enemy. Much if not all of the Nissan battery pack could fit under the Mercedes near the front of the vehicle. As much of the Nissan drive train and charging wiring harness should be used to get fast charging. You can do this with either a Leaf or a Bolt but if you make custom axles(rear wheel drive) you will be reducing weight and complexity. You will have to decide how you get the donor vehicle. If you think this method doesn't work for you, what will you get? The closer to OEM you get with the transplant the more function you will have. You could also transplant and make the vehicle FWD. That might be easier but I don't know what cross members might interfere. All in all the price you pay for a totaled vehicle will be far less than sourcing the parts individually using DIY sources. Last point the more classic or desirable your conversion the more it will be worth. That is it's better to convert a Porsche or Mercedes than a 78 Ford Fairmount. All that being said I stopped converting vehicles using DIY parts. I drive Nissan Leafs and am very happy. I couldn't possibly make as good a vehicle myself. That being said if I did convert again it would be an Ultravan RV with a transplanted Leaf or Tesla drive train and battery pack.


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