Hopefully someone here can help me. I want to add another battery to my 2019 radcity. I called rad and they wanted me to get another battery from them for $650. I have looked at a lot of forums, and battery sites, and it was too complicated. It shouldn't be. The battery on the my rad is 48 volts 14ah. There is only 2 wires going to the controller, a + & -. I can get a 48 volt 13ah (0-1000) watt 2 wire on amazon for $269. https://a.co/d/9WuWnQd My plan is to mount this in my rear rack. I will run the two wires from the back up battery to where the original battery plugs into the controller. When my main battery goes dead, I will unplug it from the controller, & plug the back up battery into the controller. It would be nice if I could buy a wire harness that had the same plug ins, but if not, i will make my own. I checked around, & some guy said he had something like that, but was out of stock, and I think it was for mounting parallel. I appreciate any help you people can give me.