Quote:
Originally Posted by Tony Raine
i guess what i am saying is that i don't really need to do it, i just want to see if i can.
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If pure interest is your motivation, then go for it. If saving money is the goal, I predict you'd decide it's not worth pursuing if you properly costed it out (including scheduled battery replacement).
To answer your controller question: no, you don't strictly need one for a DC motor. You can do what was done in the days before pulse width modulation controllers: use a series/parallel switching "contactor controller". EG: if you have a 72v pack, you design a 3-speed circuit that lets you use all the batteries wired for 12v for "creeping", 36v for low power, and 72v for full power.
That said, used 72v controllers are going on eBay these days for a couple hundred bucks.