The battery used in most power wheelchairs is a (deep cycle) lead acid battery that is either a wet cell, a gel cell, or an AGM (absorbed glass matt) battery. Although they look and feel similar, electric wheelchair batteries shouldn’t be confused with car batteries. They are vastly different in design and use and should never be interchanged.
Wet cell batteries typically hold a charge for longer and offer more power than the gel cell variety. There major drawback comes down to maintenance issues and leakage during transport. Wet cell batteries are relatively inexpensive compared to gel cell and thus are still very popular.
Gel cell batteries were developed to alleviate some of the safety and maintenance concerns that were involved in transporting an electric wheelchair. Gel cell batteries are sealed and dry with no potential for spills. This is due to the silica gel that suspends the acids (electrolyte) in the battery. So if they are broken or punctured they will not leak. The disadvantage of gel-cell batteries is that they usually have less capacity and are a bit more expensive.