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Rechargeable battery

technology Maturity 11-13 Next article →

A rechargeable battery, also known as a secondary cell or an accumulator, is a device that stores electrical energy for later use. Unlike primary batteries, which are disposable and must be discarded after one use, rechargeable batteries can be charged and discharged many times. The term "accumulator" describes how these devices gather and store energy through a reversible electrochemical reaction. These batteries are essential for modern life because they provide portable power and help stabilize electrical networks. They come in many forms, from tiny button cells to massive megawatt systems used to stabilize power distribution.

Charger
Charger

The working mechanism of a battery relies on moving electrons through a chemical process. During the charging phase, the positive active material undergoes oxidation, which releases electrons. At the same time, the negative material undergoes reduction, which means it absorbs those electrons. This movement of electrons creates the electrical current that flows through an external circuit to power a device.

Charge discharge secondary batterie
Charge discharge secondary batterie

An electrolyte facilitates this process by allowing ions to move between the electrodes. In some chemistries, like lithium-ion or nickel-cadmium, the electrolyte acts as a buffer for ion flow. In others, such as lead-acid cells, the electrolyte is an active participant in the chemical reaction.

There are many different types of rechargeable batteries defined by their chemical compositions. Common varieties include lead-acid, zinc-air, nickel-cadmium (NiCd), and nickel-metal hydride (NiMH). Modern technology often relies on lithium-based chemistries, such as lithium-ion (Li-ion), lithium iron phosphate (LiFePO4), and lithium-ion polymer (Li-ion polymer).

Lithium-Ion Cell cylindric
Lithium-Ion Cell cylindric

Each type has specific characteristics regarding how it holds a charge and how it can be used. For instance, some newer NiMH batteries are designed with low self-discharge properties. These can hold their charge for many months and are often sold from the factory at about 70% of their rated capacity.

Charging a battery requires a power source with a voltage higher than the battery's own voltage. This difference in voltage forces the current to flow into the battery. Charging speeds vary greatly depending on the equipment used. "Dumb" chargers without sensors may take 14 hours or more to reach a full charge. Rapid chargers can complete the task in two to five hours, with some specialized models taking only fifteen minutes.

Solar AA charger 01 Pengo
Solar AA charger 01 Pengo

Because fast charging can cause overheating, these chargers must use sensors to monitor temperature and voltage. Some even use cooling fans to protect the cells. Incorrect charging is dangerous and can cause batteries to overheat, catch fire, or vent their contents.

Bloated rechargeable batteries
Bloated rechargeable batteries

Engineers often measure battery performance using the "C rate." This is a theoretical measurement of how quickly a battery can be charged or discharged. A C rate of 1C means the battery would be fully charged or empty in exactly one hour. For example, trickle charging might occur at a C/20 rate, which takes 20 hours. The amount of energy a cell can actually provide depends on the discharge rate and internal resistance. In lead-acid cells, Peukert's law describes how the relationship between time and the discharge rate affects usable capacity.

Ragone-Diagramm
Ragone-Diagramm

Batteries are used in a massive range of applications across the globe. Small rechargeable cells power portable electronics, tools, and household appliances.

Nokia Battery Hologram
Nokia Battery Hologram

Larger, heavy-duty batteries are found in motorized wheelchairs, golf carts, electric bicycles, and forklifts. They are also critical for road vehicles like cars, vans, and trucks, as well as trains and even small airplanes. In large-scale systems, batteries are used for load-leveling. This means storing energy during times of low demand to use during peak periods.

Datacenter Backup Batteries
Datacenter Backup Batteries

This is especially useful for storing renewable energy, such as power from photovoltaic arrays, to be used at night.

Maintaining battery health is vital to prevent permanent damage. One serious risk is cell reversal, which occurs when a cell's polarity is switched. This can happen if a battery is connected to a charger incorrectly or if a multi-cell battery is deeply discharged. When cells in a series have different capacities, one might discharge faster than the others, forcing current through the empty cell.

Lithium Ionen Akku Überwachungselektronik
Lithium Ionen Akku Überwachungselektronik

To prevent this, many devices include a low-voltage cutoff. Additionally, leaving lead-acid batteries in a fully discharged state for too long can cause sulfation. To keep batteries healthy during storage, it is often recommended to maintain a charge level between 30% and 70%.

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🖼️ Images & Media (10)
File:Datacenter Backup Batteries.jpg
Datacenter Backup Batteries.jpg
File:Nokia Battery Hologram.jpg
Nokia Battery Hologram.jpg
File:Charger.jpg
Charger.jpg
File:Lithium-Ion Cell cylindric.JPG
Lithium-Ion Cell cylindric.JPG
File:Lithium Ionen Akku Überwachungselektronik.jpg
Lithium Ionen Akku Überwachungselektronik.jpg
File:Bloated rechargeable batteries.jpg
Bloated rechargeable batteries.jpg
File:Solar AA charger 01 Pengo.jpg
Solar AA charger 01 Pengo.jpg
File:Charge discharge secondary batterie.png
Charge discharge secondary batterie.png
File:2014 BYD E6.jpg
2014 BYD E6.jpg
File:Ragone-Diagramm.svg
Ragone-Diagramm.svg
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