The basic needs of most people will be satisfied with the standard 36V 10Ah battery. It usually provides more than enough power and range, and it’s the most affordable option.
The extended range 36V 15Ah battery is best for trips over 20 miles or if you plan to pedal very little (or not at all). It can really come in handy to have excess capacity.
The more powerful 48V 10Ah battery is best for riders over 180 pounds and for overcoming steep hills or strong headwinds. The extra power makes it more fun and exciting to ride.
The 48V 15Ah battery is the best of both worlds, and it’s the most popular option. It has all the power of the 48V 10Ah battery and the extended range of the 36V 15Ah.