Batteries connection for 3 wheel e-bike
If you connect five 12v batteries in series, you will end up with a 60v battery.

If the five batteries have different capacities, then on discharge, the lowest capacity battery / batteries will be discharged before the others. When this happens, you must stop drawing power. If you don't, the discharged batteries could be discharged to damagingly low voltage levels, and if you still draw power, become reverse charged (properly damaged!) by the others.

To avoid this happening, it necessary to monitor the voltage of each battery, or at least the low capacity ones, individually, and stop drawing power once the first battery reaches its minimum safe voltage. 

Of course, this will happen while the other batteries still have charge, so a series arrangement of different capacity batteries will be heavier and more expensive than a matched set that can deliver the same total energy.

It's worth noting that 60v is higher than most authorities would rate as a touch safe low voltage. 48v is generally reckoned to be the highest you can go before you need to start paying proper 'high voltage' attention to insulation and separation gaps.