Reserve battery facts for kids
A reserve battery is a special type of battery that is designed to be stored for a very long time without losing its power. Unlike regular batteries you might use every day, a reserve battery is not active until you need it. Think of it like a toy that comes in pieces and you only put it together when you want to play.
The main reason these batteries are used is for long storage. Their active parts are kept separate. This stops the battery from losing its charge over time, a process called self-discharge.
A reserve battery is different from a backup battery. A reserve battery is completely "asleep" until it's activated. A backup battery, however, is already working and ready to provide power, even if it's not currently being used.
These special batteries are often found in radiosondes (weather balloons), and other specialized equipment that needs power only at a specific moment.
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How Reserve Batteries Are Used
These batteries are used in devices like radiosondes, which are instruments sent into the atmosphere to collect weather data. They are also used in various specialized systems where power is needed quickly and for a short time.
You might have seen a similar idea with "dry charged" car batteries. For these, the liquid (electrolyte) is added only when you buy the battery. Another example is some zinc-air batteries. These batteries are sealed until you're ready to use them. You remove a small tab to let air in, and that activates the battery.
Making Them Work: Activation
Reserve batteries can be activated in different ways. Sometimes, you add water or a special liquid called an electrolyte. Other times, a gas is introduced into the battery. This gas can be part of what makes the battery work or part of the liquid inside.
Another way to activate them is by heating a solid electrolyte. When it gets hot enough, it becomes able to conduct electricity.
The missing part of the battery can be added in several ways before it's used. You might add water or electrolyte by hand. Some batteries activate when the system they are in is dropped into water, like in a sonobuoy (a device used underwater).
Sometimes, the electrolyte is stored in a small container inside the battery. It can be released by a mechanical push, an electrical signal, or even by the spinning or shaking of the device.
A special type called a molten salt battery is activated by lighting a small heat source inside it. This heat melts the salt, making it conductive. These batteries provide power for a short time, usually from seconds to a few minutes. However, some of these "thermal batteries" can be stored for ten years or even longer without any problems.
Reserve batteries are not very common for everyday uses. This is because they cost more and don't last very long once they are activated.
In some specialized equipment, reserve batteries use a small tank of pressurized air. This air pushes the electrolyte from a storage tank into the battery.
Types of Reserve Batteries
Here are some examples of reserve batteries:
- Aluminium battery: This is a type of zinc-air battery that uses aluminum and air to create power.
- Silver-zinc battery: These batteries were often used in older specialized equipment.
- Thermal battery: This group of batteries uses molten salt as their electrolyte. The battery stays inactive until the salt melts from heat. They are often used in specialized equipment that needs power very quickly. Examples include devices used in space exploration or for quick-response systems.
- Water-activated battery: These batteries need water to be added to them to start working. Examples include brands like HydroPak or NoPoPo.
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