A reserve battery, also called stand-by battery, is a
primary battery where part is isolated until the battery needs to be used. When long storage is required, reserve batteries are often used, since the active chemicals of the cell are segregated until needed, thus reducing
self-discharge
Self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes or any external circuit. Self-discharge decreases the shelf life
Shelf life ...
.
A reserve battery is distinguished from a
backup battery A backup battery provides power to a system when the primary source of power is unavailable. Backup batteries range from small single cells to retain clock time and date in computers, up to large battery room facilities that power uninterruptible po ...
, in that a reserve battery is inert until it is activated, while a backup battery is already functional, even if it is not delivering current.
Uses
These batteries are used in
radiosonde
A radiosonde is a battery-powered telemetry instrument carried into the atmosphere usually by a weather balloon that measures various atmospheric parameters and transmits them by radio to a ground receiver. Modern radiosondes measure or calcula ...
s,
missile
In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocke ...
s,
projectile and
bomb fuzes, and various
weapon systems.
While not advertised as reserve batteries, the principle is illustrated by the sale of "dry charged"
car batteries where the electrolyte is added at the time of sale. Another example is
zinc-air batteries where the cell is sealed until use: a tab is removed to admit air and activate the cell.
Activation
Reserve batteries may be activated by addition of water, by adding
electrolyte, by introducing a gas into the cell that is either the active cathode material or part of the electrolyte, or by heating a
solid electrolyte to a temperature at which it becomes conductive. The missing element of the battery can be added before use in several ways. The battery can have water or electrolyte added manually, the battery can be activated when the system is dropped into the water (such as in a
sonobuoy
A sonobuoy (a portmanteau of sonar and buoy) is a relatively small buoy – typically diameter and long – expendable sonar system that is dropped/ejected from aircraft or ships conducting anti-submarine warfare or underwater acoustic rese ...
), or electrolyte can be stored in a capsule within the battery and released by mechanical means, an electrical trigger, or by spin or shock. A
molten-electrolyte battery is activated by igniting a
pyrotechnic heat source. The battery delivers current for a short time (seconds to a few minutes), but some thermal batteries can be stored ten years or more without deterioration. Reserve batteries remain uncommon in civilian applications because of their higher cost and relatively short life after activation.
In missiles, reserve batteries typically use a small container of pressurized air to force the electrolyte from a storage tank into the battery. For safe disposal, the air must be vented.
In ordnance, the batteries are activated by acceleration during gun firing, or by spinning the projectile in flight.
[http://www.wipo.int/pctdb/en/wo.jsp?wo=2005093883&IA=WO2005093883&DISPLAY=DESC ]
Types
Some reserve batteries are:
*
Aluminium battery, a variant of
zinc-air battery where aluminium and air are used
*
Silver-zinc battery
A silver zinc battery is a secondary cell that utilizes silver(I,III) oxide and zinc.
Overview
Silver zinc cells share most of the characteristics of the silver-oxide battery, and in addition, is able to deliver one of the highest specific energi ...
, often found in old missiles
*
Thermal battery, a class of battery types with molten salt as an electrolyte. The battery is in an inert state until the electrolyte melts through heating. Common in military applications, especially for missiles and
proximity fuzes. Examples include
V-2 rocket
The V-2 (german: Vergeltungswaffe 2, lit=Retaliation Weapon 2), with the technical name ''Aggregat 4'' (A-4), was the world’s first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was develop ...
s,
AIM-9 Sidewinder
The AIM-9 Sidewinder (where "AIM" stands for "Air Intercept Missile") is a short-range air-to-air missile which entered service with the US Navy in 1956 and subsequently was adopted by the US Air Force in 1964. Since then the Sidewinder has prove ...
,
MIM-104 Patriot,
BGM-71 TOW
The BGM-71 TOW ("Tube-launched, Optically tracked, Wire-guided") is an American anti-tank missile. TOW replaced much smaller missiles like the SS.10 and ENTAC, offering roughly twice the effective range, a more powerful warhead, and a greatly ...
,
BGM-109 Tomahawk, many nuclear weapons, and other single-use applications.
*
Water-activated battery, a class of batteries where the electrolyte is water that has to be added, such as HydroPak or NoPoPo.
See also
*
List of battery types
This list is a summary of notable electric battery types composed of one or more electrochemical cells. Three lists are provided in the table. The primary (non-rechargeable) and secondary (rechargeable) cell lists are lists of battery chemistry. ...
References
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Battery applications