# Series/parallel switching question



## powerhouse (Apr 1, 2011)

If you aren't looking to go all out with a high current, high voltage (mainly voltage), it may not be cost effective to go direct drive. 
In order to go direct drive, you need some serious voltage to back it up. 
Parallel/series switching is always an option, but only possible through dual motors. 
A transmission will allow you to remain in the most efficient operating RPM, and also allow for some quick accelerations with a single motor.


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## major (Apr 4, 2008)

DaveAK said:


> I've just purchased a '72 Jensen Interceptor MkIII that's missing its engine and transmission. It's a long term project as it needs serious bodywork repairs, but since the drive bay is completely empty I'm toying with the idea of an EV conversion. With no transmission I was thinking of direct drive and using a dual motor series/parallel setup. Of course, since it originally came with a Chrysler 440/7.2L that's a fun sounding plan too! I reckon that either option will end up costing a similar amount.
> 
> I'm probably 2 or 3 years away from getting to the point of working on the drive train, but might as well start planning anyway. So my question is series/parallel dual motor, or a bigger single motor? Both options would be direct drive with no transmission. I'm not looking for blistering acceleration or high top speeds, but it does need to have at least a little poke to it.


Hi Dave,

We just had some discussion about that here: http://www.diyelectriccar.com/forums/showthread.php?t=67412 Personally I like the single motor approach. But it depends on your project, objectives, available equipment and so on. There have been other discussions about it in the past. It's just difficult to find threads like that.

Regards,

major


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## DaveAK (Jun 28, 2009)

powerhouse said:


> If you aren't looking to go all out with a high current, high voltage (mainly voltage), it may not be cost effective to go direct drive.
> In order to go direct drive, you need some serious voltage to back it up.
> Parallel/series switching is always an option, but only possible through dual motors.
> A transmission will allow you to remain in the most efficient operating RPM, and also allow for some quick accelerations with a single motor.


What do you consider "serious voltage"? I haven't even got so far as to consider the RPM I'll need to be honest. If I do this I'll be going lithium without a doubt, and the money I would spend on a transmission I could spend on the batteries.



major said:


> Hi Dave,
> 
> We just had some discussion about that here: http://www.diyelectriccar.com/forums/showthread.php?t=67412 Personally I like the single motor approach. But it depends on your project, objectives, available equipment and so on. There have been other discussions about it in the past. It's just difficult to find threads like that.
> 
> ...


Thanks for the link! I'll do some more digging around the site and see what I can dig up. Right now it's all just musings on my part as I have a zero dollar budget and I've already spent $800 of it.  I'm not looking to spin the tires, and I don't need to do 100mph, but that's about as far as I can define things right now. If something like an 11" Kostov will meet my needs then that would be an easier approach. I just don't want to source a transmission just to get a couple of gears if I can avoid it.


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## DaveAK (Jun 28, 2009)

Well I guess Kostov aren't going to make it easy for me to decide as they offer these two motors:

9" Dual motors

13" Direct drive


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## CrazyAl (May 9, 2011)

I'm assuming the differentials and tailshaft are still in the car.
Just wondering what is the ratio of the diff?

Out of interest, has anyone seen or know if available a big version of a motor/transaxle combination (not sure if I'm using the correct terminology here), similar in set up to the Mitsubishi i-MiEV (except a bigger version)?

I have a 1985 W123 Mercedes 280E sitting in my back yard with no motor, no transmission, no tailshaft and no differential and finding a manual transmission for it is difficult (in Australia).
I'm exploring various other options for this Merc such as underdrive/overdrive systems as a 2 speed transmission, direct drive and hub motors or even sourcing a manual transmission from either another car or from overseas.


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## Duncan (Dec 8, 2008)

Hi CrazyAl

Have you looked at Subaru bits for your diff and rear end?

They are about the most common RWD bits available here in NZ


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## DaveAK (Jun 28, 2009)

CrazyAl said:


> I'm assuming the differentials and tailshaft are still in the car.
> Just wondering what is the ratio of the diff?


Diff but no tailshaft. I think the original diff ratio was in the low 3s. The Kostov site recommends a 3.5:1 to 4:1 ratio, which is handy because I can get a 3.73:1 put in it.

Right now I've swung back to putting the original 440ci/7.2L engine back in. But that might change when I get closer to having to make that decision.


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## CrazyAl (May 9, 2011)

Duncan said:


> Hi CrazyAl
> 
> Have you looked at Subaru bits for your diff and rear end?
> 
> They are about the most common RWD bits available here in NZ


Hi Duncan,

I have not looked into Subaru bits, but I'll keep my eyes open, but here is a pic of a Mitsubishi i-MiEV rear end transaxle which I would like to emulate, but suitable for my Mercedes 280E. The only thing with the i-MiEV is that it does not have independent rear suspension where as the Merc did.









Thanks


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