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Choosing a Cordless Drill Driver: Glossary of battery terms

Glossary of battery terms

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Confused woman in a red top with a question mark over her head When learning about rechargeable batteries, you may come across some of the following phrases. Although they may sound confusing, don’t be put off, there is always a simple explanation.

Amp hours

red alarm clock and a blue drill Battery capacity is measured in amp hours.

A battery with a 1 amp hour capacity can deliver an electrical current of 1 amp for the duration of 1 hour, (or 2 amps for 30 minutes, 3 amps for 15 minutes and so on…)

Battery capacity

Battery man holding a bolt of lightning Battery capacity is how much electrical charge a battery can store.

Battery life

RIP battery written on a gravestone with the moon behind it Battery life is how many full charge cycles a battery can complete before it needs to be replaced.

Battery voltage

Voltage symbol - yellow and black lightning blot in a triangle Voltage is the electrical pressure inside the battery.

Charge cycle

One charge cycle, battery fully charged, battery running down, battery empty and battery charging up in a cycle If a battery is at full power and it runs out completely and then is charged up to full power again, that is 1 full charge cycle.

Memory effect

Battery with plus and minus symbols in a black box The term ‘memory effect’ is used when a battery does not perform as well as it could.

This can happen when batteries get old, as they don’t last forever, but more commonly it is the result of the battery being charged incorrectly.

Rechargeable cordless drill driver battery set Memory effect only occurs with certain types of battery. If you have a battery that can suffer from ‘memory effect’, only recharge it when the tool runs out of power and comes to a stop. If a battery is put on charge while it still has a lot of power remaining, then the battery will ‘remember’ this, and the next time, will not charge fully.

If a battery does not suffer from memory effect, you can use it or recharge it at any point during its charge cycle without having to worry about decreasing its life. For more information, see our section: What are the different battery materials?

Recharge time

A plug plugged into a socket The time it takes for a battery to reach full power when it’s placed on charge.

Self discharge rate

cardboard box plus a battery Discharge simply means ‘to lose charge’.

All batteries lose charge naturally when they are not being used and for some types of  battery, this happens a lot quicker. For example, nickel-based batteries have a higher self-discharge rate than lithium-ion ones, meaning they lose their charge quicker when not in use.

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