Wheelchairs and scooters use deep cycle wheelchair batteries because these batteries provide non stop power supply continuously for a certain period of time.
Basically there are 3 types of batteries
Lead acid batteries : Lead acid batteries are wet cells. They are expensive, need regular maintenance. They are not 100% safe. Risk of acid spillage and blow-up can happen. But they last long and can yield 20 - 30% more life time.
Maintenance free Lead acid batteries : They are dry cells. They are absolutely maintenance free. Completely sealed. No risk involved.
Gel batteries : These wheelchair batteries are most commonly used batteries in wheelchairs and scooters. They are also completely sealed. Require zero maintenance. Expensive of all types of batteries. Absolutely no risk involved. Life is shorter than other batteries.
Battery chargers : Different batteries use different chargers. There are basically two different models.
Built-in : These charging units are built inside the body of the scooter.
External chargers : They are separate units and the cost is included in the price of the wheelchair or the scooter.