SLA Battery Types
There are two common types of SLA battery, general standby (permanently charged) and cyclic use (charged, then discharged).
Standby SLA batteries are designed to be normally permanently charged. Applications include security, fire, UPS and telecommunication standby systems. In the event of mains failure, they are designed to provide 1/20th of the stated capacity for 20 hours (e.g. 7Ah/20 = 350mA). IMPORTANT: To avoid damage, standby batteries should not be deep discharged below 10.5V.
Cyclic SLA batteries are designed to be charged then deep discharged repeatedly. Applications include mobility scooters and golf carts. IMPORTANT: To avoid damage, cyclic batteries must be fully recharged immediately after use. SLA batteries normally self-discharge at 3% per month and so must be fully recharged when the voltage drops below 12.30V.
SLA Battery Technology
There are two types of SLA technology, AGM and GEL.
In AGM (Absorbed Glass Mat) sealed batteries, an electrolyte paste is absorbed between the plates and a fibre glass mat. AGM technology is cheaper to produce than GEL and accounts for the vast majority of SLA sales. Applications include general standby and motor vehicles.
In GEL sealed batteries, a silica additive causes the electrolyte liquid to stiffen. GEL technology provides less instant energy than AGM but gives greater long term energy delivery. Applications include mobility scooters and golf carts.