You don't have to have RAD batteries because RAD didn't make the batteries. They very similar to the Shark batteries if not a Shark battery. The main thing you need to take into consideration is who makes the battery cells. Stay with high quality cells like LG, Panasonic, and Samsung. And if you are using batteries as you posted they do need to be the same 48v.
Take a look at the following video if you want more power and speed.
https://www.youtube.com/watch?v=By9bQH4eMdA
Take a look at the following video if you want more power and speed.
https://www.youtube.com/watch?v=By9bQH4eMdA