Another commonly-used chemistry is the sealed lead-acid battery. The flooded version is found in automobiles, but most portable equipment uses the sealed version, also referred to as gelcell or SLA.

The SLA is commonly used when high power is required, weight is not a limiting factor and low cost is critical. The typical current range of the SLA is 1/2Ah to 100Ah. Applications that fall into this category are medical equipment, computer back-up, telecommunications and emergency lighting. Because of its minimal maintenance requirements and predictable storage, the SLA should be considered first.

The SLA is not subject to memory. No harm is done by leaving the battery on float charge for a prolonged time. If removed from the charger, the SLA retains the charge four times longer than the NiCd. Based on the "per ampere-hour" cost, the SLA is the lowest priced battery.

On the negative side, the SLA does not lend itself well to fast charging. Typical charge times are 8 to 16 hours. The SLA must always be stored in a charged state because a discharged SLA will sulphate. If left discharged, a recharge is difficult or impossible.

Unlike the NiCd, the SLA prefers a shallow discharge. A full discharge causes extra strain and reduces the number of times the battery can be recharged, similar to a mechanical device that wears down when being strained. In fact, each discharge-charge cycle robs the battery of a small amount of capacity. This wear-down characteristic also applies to other chemistries, including the NiMH and to a lesser extend the NiCd.