Sealed Gel Battery ("gel cell") is a gelled electrolyte for VRLA batteries; sulfuric acid is mixed with silicon powder to make the resulting material gelatinous and immobile. Unlike fully charged wet battery lead-acid batteries, these batteries do not need to be kept upright. Gel batteries reduce electrolyte evaporation and overflow (and subsequent corrosion problems) that are common in wet batteries and have a higher resistance to extreme temperatures, shocks, and vibrations. Chemically, they are almost the same as wet (unsealed) batteries, except that the antimony in the lead plate is replaced by calcium, and gas recombination can occur.

　　With gel electrolyte, the separator is no longer a critical, difficult-to-manufacture component, and the cycle life is extended, which in some cases will be greatly improved. The use of gel electrolyte reduces the shedding of active materials from the board.

　　More importantly, real gas recombination is used to make batteries that are not "watered", so it can be called Sealed Maintenance-Free Battery. The check valve is set to 2 psi, which is high enough for complete reorganization. At the end of charging, oxygen is released from the overcharge on the positive plate. It directly enters the negative plate made of high surface area pure lead through the shrinkage cracks in the gel, and "burns" as fast as it was manufactured. The oxygen and hydrogen adsorbed on the surface of the spongy lead metal negative plate combine to make water stay in the battery.