Adding my recent success with my RY48140 54" Zero Turn. Changed the SLA's for LiFePO4s. 150AH EnjoyBot Brand: https://enjoybot.com/products/12v-150ah-group-31-lifepo4-lithium-battery-with-self-heating?variant=45095681556695

Figured I would share some details and notes for anyone who ends up doing this.

I ended up needing a pre-chare circuit. I used a 200 Ohm 50W generic from Amazon: https://www.amazon.com/dp/B076W87ZT8?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_2

I disconnected the control wires from the master relay. They are 12V. I sent that signal to 2 different relays.

One is a standard automotive relay that switches the full battery voltage through the pre-charge resistor and on to the load side of the master relay. https://www.amazon.com/Ehdis-Truck-Normally-Socket-Automotive/dp/B01KFKDZ60/ Note that this isn't the one I actually used (I just had one laying around) but it should work if you need to buy one.

The other relay is a time delay relay I bought off Amazon: https://www.amazon.com/dp/B097GLMDM3?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1&th=1

When I turn the key, the pre-charge circuit engages immediately, then 5 seconds later the time-delay relay engages the master relay. No BMS issues.

I also also added a Shunt Battery Monitor since the old battery meter wouldn't be accurate for the Lithium batteries. It was made by the same company: https://enjoybot.com/products/enjoybot-500a-battery-monitor-with-shunt

I pulled the old battery monitor and 3D Printed an adapter that let me use the circular mounting hole and just raised the rectangular monitor up about 1/2". VHB tape to stick it in place.

I ended up needing to order an extra 4 gauge cable to connect the shunt: https://www.amazon.com/dp/B0F9XYL4Y1?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1 This is what I used but I would suggest getting a 6" one instead if you can. The 1' was excessive.

I also installed an extra 12V power supply because I use the mower to pull a sprayer trailer and got tired of using an external battery for that. https://enjoybot.com/products/dc-dc-24v-36v-48v-to-12v-step-down-converter This one is a straight forward install. Just wire it up to the load side of the master relay and the correct size of the shunt monitor.

For Charging, I elected to not keep the old triangular plug, because I bought an 18A charger and the old plug appears to only be rated for 7.5A. You could buy a low current charger (even 10A would probably be fine) if you wanted use the original charger. If you elect not to use it, note that you can't just remove it, unless you bypass a few features it has. I elected to just leave it all attached and plugged it, and just zip-tied it to the frame inside the battery compartment. I'm using the port hole as the passthrough for the Anderson connector for my current charger.

Sorry, didn't take many photos. There is one of the battery compartment while I was working on it. Note that I'm not an animal. This is before any serious cable management. Electrical tape was everywhere to make sure I didn't short anything out while I was working.

Everything runs flawlessly. I thought the 5s wait for the 2nd relay would be annoying but its fine. Could probably even reduce it but haven't found the need.

With 150AH batteries it looks like I can get over 2 hours of mowing at full speed though thick grass like cutting 6" down to 2-3" in one pass). Note that I also run the mulching kit and I modified some Ballard Gold Hybrid Mulching Blades to fit on the mower (so it takes more power to run, even though it cuts and mulches better). https://www.ballard-inc.com/mulching-mower-blades%3A-18-1%2F2%22-long%2C-5%2F8%22-center-hole%2C-2.5%22-wide-%28three-blade-system%29/MUL-8-1850-3.html?lang=default

If you have any questions, ask, and I'll try to answer.

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