Rechargeable Batteries

What are NiMH rechargeable batteries?

NiMH stands for nickel-metal hydride, the usual chemistry for rechargeable cells in everyday household sizes, and most of the batteries in our range use it. A NiMH cell can be run down and recharged again and again, so a single set takes the place of a steady stream of disposables. It costs more at the outset than single-use alkaline, then pays its way as you recharge it instead of buying replacements, and it keeps a good deal of waste out of the bin.

Which devices suit rechargeable batteries?

Rechargeables earn their keep in devices that get through power quickly and see daily use: game controllers, wireless mice and keyboards, camera flashes, torches and children's toys. In these, single-use cells run flat fast and the cost adds up, while a rechargeable set simply goes back on the charger. Keep a spare set charged and waiting so nothing sits idle.

For low-drain items you rarely touch, such as a wall clock or a spare torch kept in a drawer, single-use alkaline is often the more practical choice. Rechargeable cells slowly lose charge while they sit unused, so if you do keep them on standby, top them up before you need them.

Which size and capacity of rechargeable batteries do you need?

Start with size, because battery sizes are not interchangeable. Check the marking inside the battery compartment, or on the cell you are replacing, and match it exactly. Most of the batteries we stock are small cells.

Then look at capacity, measured in milliamp hours (mAh). A higher figure means longer between charges, which suits power-hungry devices such as camera flashes and controllers. For a wireless mouse or keyboard, a modest capacity is usually plenty, and it charges more quickly. If you are replacing a set that worked well, choosing a similar capacity is a sensible starting point.

Can NiMH rechargeable batteries replace alkaline?

In most devices, yes. A NiMH cell runs at a slightly lower nominal voltage than a fresh alkaline cell, but it keeps that voltage steady until it is nearly flat, while an alkaline cell fades gradually as it drains. Devices made for standard cells generally run well on NiMH as a result.

A few devices with sensitive battery meters may warn of low power earlier than you expect, which is usually the meter rather than the cells. If a manual says to use alkaline only, follow it.

How to charge NiMH rechargeable batteries

Charge NiMH cells only in a charger made for NiMH. Never put single-use alkaline cells in a battery charger, and do not use a charger built for another chemistry, such as lithium-ion. A charger that senses when a cell is full and then stops is gentler than a basic timed model, while a charger with slots for different sizes saves you buying another.

Charge the cells for a device together as a set, and take them out once they are full rather than leaving them in the charger for days. NiMH cells do not need to be run completely flat first, so topping up whenever it suits you is fine.

How to look after rechargeable batteries

Keep the cells from a device together and use them as a matched set of the same type, size and charge level. Mixing rechargeable with single-use cells, or fresh cells with worn ones, makes the weaker cells work harder and can cause leaks. Store spares somewhere cool and dry, out of direct sun, and take cells out of anything you will not use for a while.

When a set no longer holds a useful charge, take it to a battery recycling point, such as those in supermarkets and at household recycling centres, rather than putting it in the bin.