Sentinel Glossary
Glossary of terms used in standby battery management & service
Battery
The total DC back-up power system provided by an arrangement of strings in either series, or series / parallel connections depending on voltage / capacity required.
Bloc
Short for monobloc
Cell (lead-acid)
An electrochemical cell, nominally 2 volts.
Cell (Nickel Cadmium)
An electrochemical cell, nominally 1.2 volts.
Complex Impedance
In battery terms complex impedance may be defined as the separate electrical elements of an cell, i.e. series resistance, parallel resistance, inductance and capacitance, the determination of which give insight into the cell electrochemical processes.
Electrolyte
A solution of sulfuric acid and water which conducts current through the movement of ions (charged particles in the electrolyte solution) between positive and negative plates. It supplies sulfate ions for reaction with the active material of both positive and negative plates.
Grids
A lead alloy framework that supports the active material of a battery plate and conducts current.
GEL
Another type of sealed monobloc where the electrolyte is held in a gel matrix. Performance is similar (though not identical) to that of VRLA.
GSM
Global System for Mobile communications
Hold Up Time (Autonomy)
The time period for which the battery is expected to deliver its specified current.
Intercell connections
Connections between the straps of two cells, positive of one cell to the negative of the next.
Monobloc
One or more (lead-acid) cells in a single enclosure, with one positive and one negative post / terminal, consisting of one or more electrochemical cells in series, with a total terminal potential of 2, 4, 6 or 12 volts nominal.
Note: In order to provide flexibility, some manufacturers bring out more than two terminals.
OCS
Overview & Control System; can be any equipment which can collate and analyze battery data, and in some cases visualize battery performance. Such equipment includes a dedicated Battery Monitor, PC, Building Management System, SCADA system, UPS or Intelligent Charger.
Open Circuit Voltage (OCV)
The voltage of a battery when it is not delivering or receiving power. It is 2.11 volts for a fully charged battery cell.
Plates
Flat, typically rectangular components that contain the active material and a mechanical support structure called a grid, which also has an electrical function, carrying electrons to and from the active material. Plates are either positive or negative, depending on the active material they hold.
Primary Supply System
The normal source of power for the load, usually AC mains.
PSTN
Public Service Telephone Networks
Separators
Porous plastic, electrically insulating sheets which allow transfer of ions between plates, but prevent physical contact between plates and resulting electronic conduction.
‘Simple’ Impedance
Although strictly all impedance are complex, in battery testing terms the ‘simple impedance’ is defined as the AC resistance of the bloc under test at a single frequency defined by RMS Vac / Iac, or similar calculation.
SoH
State of Health
SoC (1)
System on Chip (single integrated circuit)
SoC (2)
State of Charge
Standby System
The emergency back-up power source in the event of a Primary Supply System failure.
Straps or Group Bar
Lead alloy castings that connect a number of same polarity plates together in a cell and carry current.
String
An arrangement of blocs in series to give a specified terminal voltage and capacity.
Terminals
The electrical connection from the battery to the external circuit. Each terminal is connected to either the first (positive) or last strap (negative) in the series connection of cells in a battery.
Time To Run
In the event of supply failure, TTR is the calculated remaining time that the battery will be able to supply the critical load. (Usually calculated to a specific VPC end voltage)
Vents
Components that allow gasses to exit the battery while retaining the electrolyte within the case. Can be permanently fixed to the cover or removable, depending on battery design.
VPC
The potential difference between positive and negative terminals of a single electrochemical cell, nominally 2 volts. In a monobloc, VPC will be the nominal terminal voltage divided by the number of cells in the bloc. (i.e. in a nominally 12V bloc it is 12/6 = 2V)
VRLA, SLA, AGM
Valve Regulated Lead Acid, Sealed Lead Acid, Activated Glass Mat; A ‘reduced maintenance’ type of sealed monobloc, using recombination technology to avoid major electrolyte losses through gassing. The electrolyte is minimal, typically only moisture wicked into glass pads. A valve is provided to prevent a build-up of pressure in case of over charge.
VLA, FLA
Vented Lead Acid, Flooded Lead Acid; Traditional types of cells with liquid electrolyte, utilizing clear glass or plastic cases.