Michael Ross wrote:
I have an old simple ICE push mower, that might be worth converting.
I've done some conversions, both for myself and for friends.
A standard ICE push mower, or corded electric mower is easy to convert;
but likely to be less than satisfactory to use. The weight of the
batteries will make it a bear to push around. You'd want to use better
wheels, and that gets to be a lot of work to change.
I converted a corded electric mower to battery by adding 60 2v 2.5ah
lead-acid "D" cells. They were packaged into a donut-shaped box that sat
around the existing 120vdc motor. The stock on/off switch operated a big
relay that actually switched the motor. *Don't* use the stock switch to
switch DC to the motor! It will fail almost immediately!
The batteries gave me a mowing time of 15-20 minutes. That was kind of
short, but kept the mower from being too heavy.
A treadmill motor is a reasonable choice with a high voltage battery
pack. They typically draw 5-15 amps. You will need at least 48v for
reasonable speed.
I've also converted small riding mowers. They have the advantage of more
room for batteries, and thus longer mowing times. They can also carry
the weight better. The electric motor doesn't need to be even *remotely*
as much horsepower as they advertise for ICE engines. We converted a
Wheel Horse garden tractor where the 12hp gas engine was replaced with a
1.5hp 36v electric motor. The electric was faster, and had more mowing
power than the ICE.
Avoid mowers and tractors with hydrostatic drives. They are woefully
inefficient. Get one with a mechanical transmission.
On the blade hitting rocks: Copy the same setup they use on the ICE.
They always have some kind of clutch setup so if the blade hits
something, it can instantly stop while the clutch slips. Usually, the
clutch is nothing but a big bolt that pinches the blade between a pair
of friction washers.
Golf carts and small industrial vehicles are common sources of electric
24v to 48v DC motors.
You usually don't need a speed controller. With a PM motor, all you need
is an on/off switch. A "start" switch that puts a resistor in series
with the motor for starting can also help reduce the starting current surge.
--
If we knew what we were doing, it wouldn't be called research, would it?
-- Albert Einstein
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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