I bought this Bafang 48v 500w kit from amazon with the 850-C display.
https://www.amazon.co.uk/Bafang-Conversion-Wheel-Bicycle-Display/dp/B07PDLLKRF/ref=sr_1_3?dchild=1&keywords=Bafang%2B48v%2Brear%2Bhub%2Bkit&qid=1618775165&sr=8-3&th=1&psc=1
I also bought a 48V 17.5ah battery with it. With...