I've been collecting parts for about a year and am finally ready to start building.
Snapper SPX 2242 (Pretty standard MTD hydrostatic riding mower from 2015-ish)
3 Ryobi 40V Brushless Push Mowers (2x RY401011 and 1 self-propelled RY401012)
My father-in-law acquired the riding mower for free and only planned on scavenging the ICE from it. I got 4 of the Ryobi mowers in a lot for about $200.
I plan to integrate the riding mower and push mower safety systems while keeping the riding mower looking at stock as possible. The drive motor will be wired to be started with the key switch. The riding mower utilized an electric clutch for the mowing deck, so I'll wire that switch to start the mowing deck. The existing seat switch will be wired into the push mower's safety circuit to cut power to the blades. The deck will still be removable and power will be delivered via a "standard" household 3 prong locking plug and outlet. The push mower LED headlights are usually on anytime a handle switch is depressed, but I'll wire them through the riding mower's existing headlight switch because it's there.
I've been waffling back and forth for months on how I wanted to power this 36/40V system. Did I want to use 3 12V deep cycle lead-acid batteries, 3 12V 30+Ah lithium packs, or a single large 36V lithium pack? I had dismissed the stock push mower batteries early on, but after finding a similar build online, I have come back around to the idea. I may still move to a higher capacity lithium pack in the future, but the Ryobi batteries should get me started.
A similar build
While researching lithium batteries to use in this project I came across this YouTube video posted only a month ago where he built basically the exact same build as I have planned. His Yard Machines is another MTD re-brand, and he is using the same 40V Ryobi motors as me. His build inspired me to use the stock Ryobi batteries instead of something more elaborate. One difference between our builds, he installed a speed controller on his drive motor to control the speed instead of running it full speed and using the transmission to control the speed. As a bonus, his videos serve as validation that my plan to use the push mower as a drive motor will/should work
Real-time battery life test (~43 minutes):
Donor Equipment Pictures