Why is the 20AH cheaper?the Rio uses 50-cell casing, the 48V 17AH that Damian mentioned uses 65-cell casing, they are taller but still fit. The Rio 17AH battery is made with 10S5P in NCR Panasonic cells for 10S5P, cost: £399. I can fit 10S6P 20AH into a 65-cell casing. The cost for the 20AH would be £369.