Lead acid rechargeable batteries are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, they are able to supply high surge currents, meaning that they are able to meet the power requirements of applications such as storage in back-up power supplies in mobile phone towers.These sealed lead acid batteries have many used in the today's world. They come in a wide range of sizes, typically with voltages of 6V to 12V. Some typical uses are:Emergency LightsUninterruptible power supplies (UPS)Alarm SystemsCommunication SystemsGEL Vs AGM Lead Acid BatteriesAGM (Absorbed Glass Mat)These batteries contain only enough liquid to keep the specially designed glass mat wet. The glass mat is made to wick the battery electrolytes between the battery plates. If the AGM battery is broken no free liquid leaks out.AGM batteries are preferred when a large amount of amps are required. The life expectancy remains excellent in most cases, if they are not discharged more than 60% between recharges and/or recharged fully every 3-6 months.Gel Cell BatteriesThese batteries contains silica type gel, which is a thick paste like material. It allows the electrons to flow between plates, but will not leak in a gel battery if the case is broken.Gel Cell Batteries don't offer the same power capacity as do the same physical size as AGM batteries. Gel cell batteries excel in slow discharge rates and slightly higher operating temperatures and with excellent deep cycle capability. Recharging these batteries must be done correctly or it will suffer a premature failure."What are lead acid rechargeable batteries used for?Lead acid batteries are widely used if surge current is critical, even if other designs could provide higher energy densities. Large-format lead acid designs are widely used in settings like hospitals, and in stand-alone power systems. Their surge current properties make them attractive for use in motor vehicles to provide the high current required by starter motors.How do lead acid rechargeable batteries work?The oxygen in the active material (lead dioxide) reacts with the hydrogen ions to form water, and the lead reacts with sulphuric acid to form lead sulphate. The ions moving through the electrolyte then create the current flow.