"Michael" wrote in
:

So, does anyone know where I can find a large enough motor, ideally
with the electronics to control it? The onboard power will be provided
for by two 12V batteries,
of which the AH is still undecided.


http://www.jacmacscooters.com/xtr_se450.htm
(I know nothing of this dealer. Just use his website to show it.)
He has all the parts, it says, you're looking for.

The batteries are under the floorboard with the controller in front. The
batteries are also in a nylon carry case so you can easily swap battery
packs and keep riding, charging one while riding another.

My electric powerboard (skateboard) has a 450 watt, 24VDC chain-drive motor
on it. Speed is controlled by a pulse-width modulator from a jetski-like
finger throttle on the handle bars and is very smooth, limiting current
even stalled and speed to 16 mph. The brand is Blade-Z. This motor is air
cooled, but the smaller 350 watt motors are not. They simply get hot.

Power for the scooter is twin 12AH 12V AGM batteries in series. The
scooter came with gelcells, but they were really cheap and, I thought, poor
condition as they were quite discharged by the time I got them. 12AH, 24V
will power the scooter at 16 mph for 8 miles, 30 minutes, but much longer
if you reduce throttle, reducing pulse-width duty cycle. At 8 mph, it goes
nearly 20 miles on a charge. Charger is a 2.5A 24V switching power supply
that powers automatic charging electronics built into the controller board
aboard the scooter. It charges in about 3 hours because the controller
board will not permit dangerous deep cycling of the batteries. The
controller monitors battery voltage and displays on a tri-color LED green
for good, yellow for caution and red for you'd-better-get-your-ass-to-the-
charger-cause-I'm-gonna-shut-'er-down-in-2-minutes mode. At the pre-
determined cutoff point, the controller blinks the LED solid red and
refuses to power the motor.

This whole thing would be ideal for what you're looking for. The input to
the controller is a slide resistor you could easily substitute with an
analog transistor amp, or drive the slide resistor from a radio servo.

I weigh 250# and the 450W motor has no trouble powering me up the hill
behind the house, even in the "red zone". It goes just as fast near dead
as it does full charged because of the electronic controller, which only
powers the motor at full DC when climbing out at lower speeds.

Google search on BladeZ or electric scooter parts to find the
guts of it. They're all available worldwide to fix it. My motor is like
$72, about the cost of a set of AGM replacement batteries.

ON TOPIC - If your boat is a mile down the dock, these easy-to-ride, easily
controlled scooters are excellent transport from the parking lot. Remove
the seat, fold down the handle to horizontal and it locks in place to form
the carrying handle of the 50# scooter (incl batteries) for easy storage in
a car trunk or that unused quarter berth. You don't HAVE to arrive at the
remote marina stranded, you know. The flat platform for your feet is just
as long as a briefcase is wide and its width is about 3 briefcases. A
carry basket fits behind the seat but you can strap a BIG suitcase to the
seat and ride it on top of the very heavy wheel fender. I paid $299 for it
at a local sporting goods store on sale.

http://www.jacmacscooters.com/xtr_se450.htm

--
Larry