I'm putting my spare battery into service by running 2 batteries in parallel. I have 2 fat tire hubbers with dual batteries that make single battery setups seem feeble. This mounting plate will go on a heavy duty rear rack on my FS Ultra. Couldn't be any bumpier than the racks on the hubbers, keeps the contacts shined up. Dual batteries do more than just increase range. When a single battery is below half charge, the available power becomes increasingly unavailable due to voltage sag under load. Bellow 1/3 charge a single battery is almost useless. A dual battery setup will provide full power as low as 25% charge without issue. Useable power range is therefore more than doubled by adding 2nd battery. Why? Max current draw on a single battery is, say 30amps, with 2 batteries in parallel the max draw is only 15amps per battery. Therefore the voltage drop in each battery is minimal when under full load. A single battery will suffer severe voltage sag bellow 1/3 charge, that = no power, battery stress and will trigger the BMS into limp mode or full shut down.