How do rechargeable batteries work?

With an ever-increasing number of portable devices in our lives, rechargeable batteries of all sorts are becoming more common, and more important, than ever before.

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For a technology that the majority of us use multiple times per day, and one that has existed since the 19th century, most of us know almost nothing about how rechargeable batteries work.

How do rechargeable batteries differ from regular batteries, how do they charge, and what types of rechargeable batteries are available?

How do rechargeables charge?

All batteries function through electrochemical reactions between the contained anode and cathode. When the circuit through the battery is closed, usually by turning on the device, the electrolyte within the battery allows the anode and cathode to react with one another, producing the current that powers our devices.

Rechargeables discharge in the same way, but by using different anode and cathode materials. To charge, a charger subjects the batteries to consistent current, allowing the battery to ‘reset’ itself to its original state.

This process is not perfect, resulting in rechargeable batteries having a limited lifespan and causing the battery memory effect whereby the maximum charge a battery can hold is gradually reduced over a number of charge/discharge cycles.

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What types of rechargeable batteries are available?

Depending on a number of factors, such as required weight, volatility and cost, different types of rechargeable batteries are available.

The oldest type, developed in the mid-19th century, is the lead-acid battery. As its name implies, lead-acid batteries use a reaction between lead and sulphuric acid to provide a very high electrical current. Lead-acid batteries are very heavy but provide high current; therefore, they are often used in applications in which weight is not an issue. The include starter motors and car batteries such as the Odyssey PC680 battery available from stockists such as http://www.grovesbatteries.co.uk.

Most standard rechargeable batteries – AA, AAA and so on – were nickel cadmium (NiCd). These have largely been replaced by nickel metal hydride (NiMH) batteries, which are more expensive but hold more charge.

Most portable devices are now powered by lithium ion batteries. These are not available in standard sizes and are vulnerable to overcharging, meaning they tend to require their own chargers.

Given the number of portable devices, batteries will only become more common, especially as more technologies are sure to emerge in the near future.

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