Safety vent - A safety mechanism that is activated when the internal gas pressure rises above a normal level.
Sealed cells - A cell which remains closed and does not release gas or liquid when operated within the limits of charge and temperature specified by the manufacturer. An essential component in recombinant cells.
Self-discharge - Capacity loss during storage due to the internal current leakage between the positive and negative plates.
Series connection - The connection of positive to negative of two or more cells to form a battery of higher voltage.
Shunt regulator - A voltage regulator which uses a transistor or FET, in parallel with the load, which shorts out the excess voltage when the applied input voltage exceeds a specified limit producing a regulated output voltage. It is a simple but lossy design.
Slow charge - Charging overnight in 14 to 16 hours at about 0.1C rate. Safe and simple.
Solar cell - A photovoltaic cell. Solar cells convert sunlight energy into electric current. They do not store energy.
Solar panel - An array of photocells providing an increased output.
Solid State Battery - Cells with solid electrolytes. Lithium polymer cells are examples of this technology
Specific Gravity SG - The ratio of the weight of a solution compared with the weight of an equal volume of water at a specified temperature. It is used to determine the charge condition in lead acid batteries.
Standard charge - The normal charge used to recharge a cell or battery in 10 hours. Other definitions (charging periods) also apply.
Standby power - A fully charged battery ready to take over supplying a load in case of emergency.
State of Charge- SOC - The available capacity of a battery expressed as a percentage of its rated capacity.
State of Health- SOH - A measurement that reflects the general condition of a battery and its ability to deliver the specified performance compared with a fresh battery. It takes into account such factors as charge acceptance, internal resistance, voltage and self-discharge. It is not as precise as the SOC determination.
Storage life - The length of time a cell or battery can be stored on open circuit without permanent deterioration of its performance. See also Battery Storage
Studs - Threaded bolt connectors used on high power cells
Sulphation - Growth of lead sulphate crystals in Lead-Acid batteries which inhibits current flow. Sulphation is caused by storage at low state of charge.
Swelling - Distortion of cells caused by expansion of the active chemicals due to temperature and pressure effects.