fotajoye wrote:
I converted a old Sears hydro garden tractor to electric using four 85 amp
deep cycle Pb batteries, a 48v 200 amp alltrax controller and a 48 volt DC
motor. I soon learned the mowing load on the batteries was too high to use
the cutting deck for mowing three acres of tall pasture grass, or even 1/2
acre. What I really need is 16, 200 amp LiFePo4 cells and an intelligent
charger. At this point, while waiting for lithium to develop a good market
within my means, I have relegated the Sears machine to mule duty carrying
fire wood and other chores. Also, it's coming up on about two years now and
the Pd is giving up...needs to be replaced.
It's likely that much of your power was lost in the hydrostatic drive.
These things are woefully inefficient.
Also, how did it drive the mower deck? Often, they have an inefficient
belt drive setup from the engine to the blades.
12v batteries are often a poor choice for applications like this. Most
of them are little more than ordinary ICE starting batteries, and won't
hold up for long. There are a *few* 12v batteries that truly are
deep-cycle, but you won't find them at Sears or Walmart. They are sold
by industrial battery dealers for floor sweepers, pallet jacks, and
other commercial in-plant EVs.
They can afford to waste power with an ICE tractor, because it's a
marketing advantage to advertise "powerful 20 HP engine" (or whatever)
when only 5 HP of that is in fact used to move the tractor and blades. :-/
The old GE ElecTraks are an example of a garden tractor designed to be
electric from the ground up. It used:
- A gearbox instead of a hydrostatic drive.
- DC motors directly driving the mowing blades; no belts.
- No controller! The motor was switched straight to the batteries,
and speed was controlled by the multi-speed gearbox.
- Used six 6v golf cart batteries; a true deep-cycle battery.
The result was that the ElecTrak could mow for 1-2 hours, pull just
about anything, and even plow heavy snow. The batteries lasted about 3
times longer than the usual 12v "marine / deep cycle" batteries.
--
Scientists investigate that which already is. Engineers create that
which has never been. -- Albert Einstein
--
Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
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