Double Battery Box Kit, 2nd Gen
Running two batteries in parallel is like creating a single battery with double the capacity and double the maximum current. Take two single battery boxes and swap their lids with these double lids to turn them into a single, easy to manage unit. Slide the controller onto the side rails of the battery box and use the splitter to connect it to both batteries.
As a battery discharges, its voltage gets lower, while the voltage of the Onewheel battery gets higher. The amount of current the battery must output to bridge the gap between those voltages increases while the battery's ability to supply that current is waning. Cheaper Chinese batteries can struggle to output enough current to maintain 5A throughout the charge. When two batteries are connected in parallel, they share the load and each only needs to output half of the current needed.
Before pairing the batteries, charge each one fully using the same charger so they begin at the same voltage. If two batteries are connected in parallel, and one has a significantly higher voltage, it will charge the other battery with no way to restrict the amount of current it delivers, creating a fire hazard. After using, leave them connected and recharge them together as a unit.
The full kit is two battery boxes, double lids, and a splitter. This is not the charger, it is only boxes for the batteries.
Batteries are not included.