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VRLA Battery Glossary

VRLA Battery Glossary


Active Material
The substance which electrochemically reacts in the electrode of batteries. Lead-acid batteries adopt lead dioxide for the positive electrode and spongy lead for the negative electrode.

Ambient Temperature
Average temperature in the vicinity of the battery.

Available Capacity
The capacity actually available from a cell/battery. The available capacity is the capacity when it discharges at a specified hour rate, and expressed in hour rate and Ah.

Built-In Thermostat
The built-in thermostat is a reset table switch built in a battery for temporarily cut off the battery circuit when the temperature of the battery exceeds a preset values or when the battery charge/discharge at a higher rate than predetermined.

The electric capability of a battery. It usually means ampere-hour capacity expressed in Ah or C(coulomb).

The minimum battery unit which composes a storage battery. Nominal voltage of the cell of the lead-acid battery is 2V.

Charge Acceptance 
Test of batteries to check whether or not they are adequately recharged after discharge.

Charging Efficiency
General term for ampere-hour efficiency and watt-hour eficiency. In many cases, however,it means the ampere-hour efficiency.

Constant Current Charge
A method of charging: to charge a battery with a constant current.

A charge or discharge current rate expressed in A or mA.It is numberically the same as the hour rate capacity of a battery expressed in Ah of the rated capacity.

Cut-Off Voltage Of Discharge
The terminal voltage of a battery at which discharging should be discharging should be discontinued. This voltage depends on discharge current, type of electrodes and construction of battery.

Cycle Life 
The number of charge/discharge/rest cycles a cell/battery can provide. Cycle life is usually expressed by the number of cycles available before duation of discharge decreases to a half of the initial value.


Depth Of Discharge 

A value to express the state of discharge of a battery. The depth of discharge is generally expressed by the ratio of discharge amount to rated capacity of the battery.

Discharge Rate

The term to express the magnitude of discharge current. When assuming discharge current and time to discharge cut-off voltage t hours, this discgarge is called t-hour rate(tHR) discharge, and the current is called t-hour rate diacharge current. When time t is minutes instead of hours, tMR is used.

Duty Cycle

Test of batteries in ordinary use including charge, discharge and rest.

Energy Density 

Energy available per unit Approx. mass or unit volume of a cell/battery. Energy desity is expressed in Wh/kg or Wh/l.

Float Charge 

The system in which a constant voltage is continuously applied to a battery connected to a rectifier in parallel with a load to maintain the battery in charged state: on occurrence of power failure or load variation, the battery supplies power to the load without any short break.

Gas Recombination Ability

Capability of a battery to recombine (or absorb) internally generated oxygen gas at the negative plate. The greater this capability is, the larger the available charge current.

High Rate Discharge 

A very rapid discharge of a battery. (in many cases it means discharging at approx.1 CA or higher rate.)

Internal Pressure 

The pressure within a sealed battery. Internal pressure of a battery is increased by oxygen gas which is generated from the positive plate at the end of charging.


Internal Resistance

The resistance within a battery; it is the total of individual resistances of the electrolyte and the positive and negative plate. Internal resistance is simply measured with the current four-terminal method(1,000Hz) and expressed in the composite value of resistance component and capacitor component.

Internal Short-Circuit 

Touching of the positive and negative plates within a call.

Low-Voltage Cut-Off 

A circuitry designed to discontinue discharge of a battery at a predetermined voltage level.

Male Tab

The matallic pieces which are attached to a SLA battery as the terminals.

Memory Effect 

A phenomenon where a temporary drop of discharge voltage is observed during deep discharge of an alkaline rechargeable battery which has been subjected to shallow charge/discharge. Cycles or trickle charging over long time.

Nevigative Plate 

The battery electrode into which a current from the external circuit flows during discharging. The negative plate has lower electric potential than the positive plate to the electrolyte. The negative plate is incorporated with connection parts such as the electrode pole.

Nominal Voltage 

A nominal value to indicate the voltage of a cell battery. Generally, nominal voltage value of a battery is somewhat lower than its electromotive force. Nominal voltage of the lead-acid battery is 2.0 V per unit cell.

Open Circuit Voltage 

Measured voltage of a cell/battery which is electrically disconnected from the external circuit.

Over Charged 

Continuted charging of a fully charged cell/battery. With batteries which require watering, overcharge causes electrolysis of water, resulting in rapid decrease of electrolyte. Generally, overcharge adversely influences battery life.

Over Discharged 

Discharge of a battery to a voltage below a predetermined cut-off voltage.

Parallel Charge 

Simultanous charging of two or more batteries connected in parallel. In cyclic use of batteries, specifically, the parallel charge tends to cause an imbalance in charge state among the batteries, which may shorten their service life.

Polypropylene Resin 

A plastic material which is often used for the case and cover of batteries.

Quick Charge(Rapid Charge)

Charging in a short time with a large current.

Rated Capacity 

The stated capacity of a battery; namely, the ampere-hour amount can be drawn from the battery in fully charged state at a specified temperature, at a specified discharge rate, and to a specified cut-off voltage. The symbole CN may be used to express the rated capacity of N-hour rate.

Refresh Charge(Auxiliary Charge) 

Charging of a battery mainly to compensate for its self discharge.

Residual Capacity 

Residual capacity of a battery after partial discharge or after storage for long time.

Self Discharge 

Reduction in capacity of a battery while no current is draw by the external circuit. Self discharge depends on temperature: amount of discharge approximately doubles by each (10¡ãC) rise of ambine temperature.

Standby Use

General term of constant stand-by battery systems. Batteries are kept charged by trickle/float method at all times in preparation for unforeseen power disruptions.

Terminal Voltage At Discharge 

The voltage of a battery during discharge.

Thermal Runaway 

Such phenomena as an excessively high set-up voltage in constant-voltage charging of a battery and a very high battery temperature cause charge current to increase,which than raises the termperature further:this vicious cycle is called thermal runaway,which may,in the worst case,result in breakage of the battery due to heat.

Trickle Charge 

To charge a battery in the state of disconnection from the load to compensate for its self discharge.

Trickle Life 

The service life of a battery in the trickle use. Usually,the trickle life is the time expressed in years before the dischargeable time of the battery decreases to a half of the initial value.

Equipment or system which is automatically connected to the load to supply power if the main power fails.

Valve(One Way Valve)                                                                               

a valve on each battery which automatically releases gas from the battery when internal pressure of the battery exceeds a predermined value:it prevents breakage of the battery due to excessive internal pressure caused by the gas generated by charging or other reasons. The valve also serves to prevent outside air from entering batteries.  

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