# 7" 24v forklift motor sufficient for 30mph?



## youreakirk (May 12, 2012)

Hey all,

I have a few questions and concerns about the forklift motor we recently acquired for my Honda CRX - it is only rated to 24v and is 7" in diameter. It is an extremely light car, but I hope the motor will be enough. It was hard to beat the price (or lack thereof)...

Our goals are 30-35mph and 12 miles of range.

I've seen 24v motors used in a few conversions, *how safe is it to overvolt them? And thoughts on voltage or other battery pack specs (lead acid for cost) for the aforementioned goals? Also, is there anything we need to do before we bolt together the motor and tranny to still use the OEM spedomoter and tachometer?* Keep in mind we are high school kids with small albeit expendable incomes from summer jobs - we are trying to do a "rat rod" conversion that will get us to school and back.

Thanks! Any advice/comments/critiques are much appreciated!

Also, here are some pics!

The lift!


The motors


The drive motor


The external shaft drove a gear in the forklift tranny


Power connections


Info plate


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## major (Apr 4, 2008)

youreakirk said:


> Hey all,
> 
> I have a few questions and concerns about the forklift motor we recently acquired for my Honda CRX - it is only rated to 24v and is 7" in diameter. It is an extremely light car, but I hope the motor will be enough. It was hard to beat the price (or lack thereof)...
> 
> ...


Hi you,

The three motors you show are old Prestolite 6.6" diameter motors with the 3.25" stack core. They are probably MJT, MEA and MJN types, left to right. MJT (traction) and MEA (lift pump) are similar 37 slot series wound with 1.25 x .5 brushes. The MJN is compound wound with 59 bar wire soldered comm and 1 x .4 brushes---forgetaboutit. The lift pump doesn't have a shaft you can work with. That leaves the MJT.

It has the split field. Just leave the jumpers and run it. The spline (or gear) output shaft is trouble to couple but you could drive from the brake mount on the comm end. It likely had a 2hp one hour rating at 24V, but could handle 300 amps for accelerations. As is, 48V probably. With brush advance, maybe higher.

This 6.6 motor is too small for EVcar conversions. The newer D&D are 6.6 but longer core and comms and they are marginal for cars (and small ones at that). Because your goals are modest, the MJT could get you going. Keep the tranny as you'll need 1st gear. Don't expect too high performance, but you might be able to keep up with traffic. 

Regards,

major


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## youreakirk (May 12, 2012)

Major,

Thanks for the info. I think we will go ahead and use it - hopefully if we find another motor later we could reconfigure the adapter plate.

I will post in my other thread (http://www.diyelectriccar.com/forum...-honda-crx-conversion-p316814.html#post316814) when we get everything together.

So you're saying I could realistically run 48v without advancing the brush timing? Also do you know of a good resource regarding advancing the brushes?

Thanks again

Kirk


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## major (Apr 4, 2008)

youreakirk said:


> So you're saying I could realistically run 48v without advancing the brush timing?


Yes.



youreakirk said:


> Also do you know of a good resource regarding advancing the brushes?


It has been covered several times here. Search for it. You'll find other useful info along the way.

It may be difficult to advance on that particular motor due to the cross straps being frame mounted. Don't go there unless you need it and worry about the rest of the conversion for now.


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## youreakirk (May 12, 2012)

Sounds good, we'll just see where 48v gets us and go from there - any issues regarding wiring 48v banks in parallel as long as the batteries are all the same? Could amperage be excessive at times? I know in theory it would just extend capacity but I've only seen people wire in series in the conversions I've looked at.

Sorry for all the questions - thanks!


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## drgrieve (Apr 14, 2011)

Have a at look at builds using small ah cells like headway or A123 pouches. To increase Ah place the cells in parallel and then in series.

You can place in series and then parallel but I forget off-hand the disadvantages in doing so.


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## youreakirk (May 12, 2012)

What's the physical difference between parallel then series versus series then parallel?


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## major (Apr 4, 2008)

youreakirk said:


> What's the physical difference between parallel then series versus series then parallel?


Paralleled at the cell level keeps those cells at the same voltage so one assumes at the same charge and "balanced". A BMS cell module is required for the paralleled cell group opposed to each and every cell if they were in series cell groups and then parallel connected. Alternative methods include running BMS wires between cells in those series groups, but that becomes a spaghetti monster and the BMS wires can conduct load current in some cases and melt.

Also paralleled cell groups would likely reduce the number of high current connectors depending on the cell type and configuration.


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