Gearbox or direct drive


I am new here so I apoligise if this has been covered before. A quick search of the forum did not show anything specific.

I am looking into converting an E36 BMW sedan into an electric vehicle. While I would love to do an AC conversion they are still just too expensive. Instead I will stick with DC, probably a Netgain Warp 9 or 11.

Now to my question, should I go direct drive with a transwarp or make an adapter and keep the gearbox. Now if I were building a dragster the answer would be simpler (direct drive and lots of current!) but this vehicle is to be a daily driver with a daily range of at least 80km. I will be using 90-160Ah worth of LiFePO4 batteries at 192V and a Zilla controller. The area that I live in is quite steep with some hills up to 20 degrees or more. I want to have reasonably zippy performance.

Direct drive should be easier to package (and cheaper) since the motor will just fit where the gearbox currently lives giving plenty of room in the engine bay for batteries and so on. Keeping the gearbox will allow me to run the motor faster and give better efficiency.

Thanks in advance,


80K (48 mi) with steep hills sounds a bit optimistic for 90 ah. My little pickup truck with 80 ah has a flatland range of abt 15 - 20 mi at 30 mph.
If you can really do this, I’d love to know how.

90Ah at 192V is just over 17kwh. Looking at Wikipedia, the old Ford Ranger EV used around 500wh/mile and the BMW will be significantly lighter than that. That figure gives a range of around 34 miles (just over 50km). Lithiums do much better than Lead Acid under load so 90Ah of lithium is worth more than 90Ah of Lead acid.

That said, I have the option of going to 160Ah lithiums instead although this takes me to 336kg of batteries up from under 200kg. Still OK but not as light as I would like.


@rlaxton :
a little off-topic I know, but where are you getting your batteries from? I’m planning a conversion using a direct-drive AC motor (probably MES, maybe solectria), and I’d like to use lithium batteries too, but I’ve only found a few manufacturers that make packs (rather than individual cells), and they’re VERY expensive…


Probably go with ThunderSky or similar LiFePO4 batteries. Not cheap but probably better value in the long run than Lead Acid since 3000 cycles is what they are rated to while you would be lucky to get 500 with lead acid in an abusive EV application.