They are available in a variety of sizes, from very small button cells for hearing aids to the large batteries used in film cameras.

A battery is a device that holds electrical energy in the form of chemicals. With the help of an electrochemical reaction, it converts stored chemical energy into direct current (DC) electrical energy.

These are made in various sizes and capacities, from portable sealed to large fanned cells used for standby power and motor power. Smaller packs are used in portable devices, electronics, and toys, while larger packs are used in aircraft starting batteries and electric vehicles.

The second way they can be used is in the same way as a primary battery, the difference is that can be charged once the battery has lost its charge. Normally this will involve connecting the battery to a certain power source, such as mains electricity to charge the battery for a short time. An example of this is a laptop, when the battery is running low you simply connected it to the mains to charge again.

The fundamental relationship of electrochemical cell operation, put forth by the English physicist-chemist Michael Faraday in 1834, is that for every ampere that flows for a period of time, a matching chemical reaction or other change must take place. The extent of such changes is dependent on the molecular and electronic structure of the elements constituting the battery electrodes and electrolyte. Secondary changes may also occur, but a primary pair of theoretically reversible reactions must take place at the electrodes for electricity to be produced. The actual energy generated by a battery is measured by the number of amperes produced × the unit of time × the average voltage over that time.

Batteries were invented in 1800, but their complex chemical processes are still being studied. Scientists are using new tools to better understand the electrical and chemical processes in batteries to produce a new generation of highly efficient, electrical energy storage. For example, they are developing improved materials for the anodes, cathodes, and electrolytes in batteries.

Li-ion has by far the highest share of the dry cell rechargeable market. NiMH has replaced NiCd in most applications due to its higher capacity, but NiCd remains in use in power tools, two-way radios, and medical equipment.

The effect of increased battery material prices differed across various battery chemistries in 2022, with the strongest increase being observed for LFP batteries (over 25%), while NMC акумулатори цена batteries experienced an increase of less than 15%. Since LFP batteries contain neither nickel nor cobalt, which are relatively expensive compared to iron and phosphorus, the price of lithium plays a relatively larger role in determining the final cost.

There are a large number of elements and compounds from which to select potentially useful combinations for batteries. The commercial systems in common use represent the survivors of numerous tests where continued use depends on adequate voltage, high current-carrying capacity, low-cost materials, and tolerance for user neglect.

Battery usefulness is limited not only by capacity but also by how fast current can be drawn from it. The salt ions chosen for the electrolyte solution must be able to move fast enough through the solvent to carry chemical matter between the electrodes equal to the rate of electrical demand.

Leak-damaged alkaline battery Many battery chemicals are corrosive, poisonous or both. If leakage occurs, either spontaneously or through accident, the chemicals released may be dangerous. For example, disposable batteries often use a zinc "can" both as a reactant and as the container to hold the other reagents.

They have a long service life and are found in small portable devices such as watches and pocket calculators. It is made of stainless steel that forms the cell’s lower body and positive terminal and a metallic top cap forms the negative terminal.

Disposable batteries typically lose oito–20% of their original charge per year when stored at room temperature (20–30 °C).[57] This is known as the "self-discharge" rate, and is due to non-current-producing "side" chemical reactions that occur within the cell even when no load is applied. The rate of side reactions is reduced for batteries stored at lower temperatures, although some can be damaged by freezing and storing in a fridge will not meaningfully prolong shelf life and risks damaging condensation.

Sodium-Metal Halide: Also known as ZEBRA batteries, these hold potential as stationary batteries used to store energy for the grid. PNNL researchers have developed a design that is more stable and less expensive to manufacture, with increased energy density.