JDH: My first gas conversion - My eMower

This weekend I converted my gas lawnmower to battery powered electric!

It was really easy. Research involved reading this page: http://www.builditsolar.com/Projects/Vehicles/LeeMower.htm

Three bolts and two cables detached the gas engine from the deck. Once removed I used a Tecumseh 90000A electric motor. This is a motor designed for lawnmowers - it's rated at 1.5HP continuous (using the "peak equals 3 times continuous" rule of thumb it should be good for about 4.5HP peak - and the gas motor being replaced was rated at 4HP). The 90000A also is designed to mount to a mower deck. The downside of the 90000A is the price - about $190 - however, I decided to go this route because it greatly increased my chances of success :-)

Two out of three holes on the 90000A lined up with my Sears Craftsman 22" deck. I simply drilled out the third. The old motor had threaded holes in the motor casing - the new one didn't have threading. So, three new nuts, bolts and washers to attach the motor.

I made the battery platform by simply cutting a piece of 2 by 4 and mounting it on the deck with angle brackets. This was one end of a support for a plywood battery deck. The other end simply rests on the rear end of the deck (I use a mulching blade so I'm not concerned about restricting the movement of the rear springloaded door). The batteries sit on top of this and are strapped down with two heavy duty rubber straps. This works for my environment - you might want something more sturdy depending on your yard layout.

The circuit is as follows:

The blade mounts to the keyed motor output shaft via a rectangular blade adapter. The output shaft itself is threaded - you slip on the adapter and then the blade and bolt both to the shaft. The old one was seized tight so I ordered a new one from Sears online parts store.

Notes:
1) I don't have a deadman's handle anymore. Both the breaker and the switch are in easy reach so I'm not concerned - however, an improvement would be to use the old springloaded handle with some form of high amp limit switch. I just re-read the above page and I notice that Lee is using the deadman's handle to operate the same style of breaker that I have - so I might try that out.
2) I placed the breaker between the batteries - it was a convenient place to mount it and I switch it off to allow both batteries to be charged seperately (with cheapo $18 1.5A battery chargers from Wal-Mart)
3) The volt meter was designed to mount into a 12V power socket (cigarette lighter) - so I just wired it to one of the two batteries - should be good enough.

The original mower was self-propelled and I didn't convert that feature. I might look at dismantling the engine casing and seeing if I can somehow salvage the gearing and output shaft for the self propel mechanism. But I probably won't bother. My yard isn't that big (we inherited the mower when we bought the house - I doubt I would have ever got a self propelled mower for our small yard).

Here's the parts list:

Yes, I can get a push mower for that price - and that's even more environmentally friendly. Yes, I can get a corded or low-end cordless mower for that price. However, a few counterpoints: (a) my deck is 22" - bigger than those options, (b) my batteries are removable and cheaply replacable, (c) I already had the mower so it's more eco-friendly to recycle than replace.

BTW, my neighbor just bought a 14" mower with a plastic deck - she paid around $400 - so my $278 doesn't seem too bad.

Of course, at the end of the day I mostly did this simply because I could!

But now it's your turn - get rid of the gas in your life...