Let’s break down the cost of operation for an electric mower vs. the gas counterpart.
From some quick googling it seems the cub cadet zero turn uses 1.8 gallons of fuel per hour. Let’s round this down to 1.5GPH. Fuel cost in this area is $3.50/gallon, so
1.5GPH x $3.50 = $5.25/hour
Our electrified zero turn mows for approximately 1 hour on a 4KWH battery pack. The electricity price in this area is $.13/KWH, so
4KWH x $.13 = $.52/hour
But the electric zero turn costs more upfront than the gas version. The total part cost breakdown is as follows
3x Enerdel ME330-049 Energy @$480/ea = $1460
ME-1004 Double brush 48v motor = $525
Soliton Jr. Motor controller = $1750
PMP-450 pump, radiator, tubing = $250
——-Grand total——- $3985 dollars
So the operational cost difference is $5.25 – $.52 = $4.73/hour
And the payback time for the conversion based purely on fuel cost savings is…..
$3985 / $4.73 = 842.49 hours of operation
Upstate Electric 
that’s a great breakdown but your missing matinance costs on the gas engine, oil cost, plus cost of gas in a car to the gas station and back per trip to refill the gas can
You’ve made a common mistake. The real cost of electrics isn’t the energy to
recharge batteries. It’s the cost of the batteries themselves. They’ll have to be replaced at regular intervals every few years. The battery cost per battery lifetime is your actual “fuel” cost.
If you look at the Enerdel specs you will see that the cycle life is greater than 3000 cycles, and the calendar life is great than 10 years. I know other common LiFePo4 chemistries have demonstrated 2000-3000 cycles to ~80 original capacity. Since the payback time considering battery cost and fuel costs is ~850 hours, the expected lifetime exceeds the payback period by a factor of 3+. I can live with that
~3000 cycles … ?
Enerdel ME330-049 Moxie+ datasheet (rv. 031113):
2500 cycles @ 30degC (86degF) for 80% BOL
1250 cycles @ 45degC (113degF) for 80% BOL
It’s “cool” that we can do something like this.
I personally would rather have electrics due
to smell, leaks, and maintenance issues. But,
I just don’t find it cost justifiable in any
way at this point in time for hobbyists.
Battery costs and energy density are
the problem. The costs are too high.
The energy density is too low. The
DOE says a gallon of gasoline is the
same as 14 sticks of dynamite. That’s
huge amount of energy in a small package.
You’ve cooled the Soliton Jr. You’re not
cooling the batteries. You dump the heat
from the Soliton Jr. to mower’s radiator.
From the photo, the radiator appears to be
below the batteries, thereby heating them.
Heat kills battery life.
The batteries appear to be tightly packed
together which would fail to allow for any
natural airflow cooling from during movement.
This leads to accumulated and retained heat…
Given that you’re heating your batteries,
packed them tightly, and not cooling them at
all, I have to assume you’re much closer to
45degC. So, I seriously have to doubt your
claim of ~3000 cycles out of those batteries.
Have you even measured the temperature of
the batteries after a long mow? Can I roast
marshmallows on them? Fry an egg? You
must take into account the batteries can’t
dissipate heat during summer temperatures.
Of course, that probably doesn’t matter, as
long as this is a home use yard mower. A normal
yard mower will only see about 350 mows over
a ten year lifespan which would only need one
battery pack. If it’s being used for commercial
use, it could easily go through a three battery
packs a year to power the electric motor, whereas
a modern internal combustion engine will easily
last a decade.
Even if we price the electrified mower at
only one battery pack, e.g., home use,
it’s still more expensive to do:
CubCadet RXT VT
$3,250.00 (new 2009)
$5.25/hr gas [your number…]
350 mows @ 1hr/mow (est. 10 years)
—
$5087 total
$14.53/mow
“Electrified” CubCadet
$1,000.00 CubCadet used est.
($1,795 used 2009 in 2013, minus motor: $800 reman.)
$2,525.00 electrification cost excl. batteries
$1,460.00 one battery pack
$0.52/hr electricity [your number…]
350 mows @ 1hr/mow (est. 10 years)
—-
$5167 total
$14.76/mow
If you received a “dead” mower for free,
then the economics work as compared to buying
a new mower. But, the economics still do not
work. It only costs $800 for a remanufactured
gas engine versus the nearly $4K you spent.
That’s assuming a used, “dead” one is even
priced that low. It still has a motor that can
be rebuilt.
Your estimate of 842 hours of operation seems
to be about 24 years of home use with a large
yard… It’d only be 15 minutes of mow time
here, making it 100 years.
And, of course, I think the gasoline usage
and therefor gasoline cost of the CubCadet
are much lower than stated too.