When the 3 @ NAPA 8270s I have been using in my ER8-36 let me down last week I decided to try a 100Ah LiFePO4 golf cart conversion kit planning to use it for standby lighting in the garage too.

KeepKnow 36v100ah-522
36V (38.4V) 100Ah LiFePO4 Lithium Golf Cart Battery, Complete Upgrade Kit with Charger, LCD Display & App, Built-in 200A BMS, Max 7.68kW Power Output (36V 100Ah) with 43.8V 25A charger

Being slightly smaller than a 8D pack it fits with room to spare.  I placed the pack terminals on the right side to avoid having the cables cross, and to better accommodate the slight flexing when the clutch / brake petal shifts the drive motor.  I needed 2 @ 30" battery cables with ring terminals, and longer J-bolts for the battery hold down.

1 hour of mowing on fairly level lawn only used 17% of the capacity.

Thanks,
Bill