Recently my uncle got the 12 Volts and 12 AMP hours battery from Spin life in the Power chair, which he uses to roam in the garden area as due to certain health problem he is unable to stand on legs for long hours.
I hope your Uncle is enjoying the scooter, they can be a god send if you have mobility issues and can give your freedom back. Many members on here use mobility scooters on this site so they can give advice when needed.