If you have a digital device, your hearing aid battery is probably of a kind known as "zinc air". These are also commonly used in watches.

They have a number of advantages, such as being high energy and inexpensive. You will not need to spend much on a hearing aid battery - they cost pennies each.

Zinc air batteries, however, do need to be used quickly and may not survive being very hot, cold or humid, so they should be kept at room temperature.

You should find it easy to locate the correct size of hearing aid battery for your device, as they come in colour codes.

There are four different sizes, each of which is assigned its own colour.

Size 10 is yellow, size 312 is brown, size 13 is orange and size 675 is blue.

How long your hearing aid battery will last depends on the hearing aid itself, the level of amplification you need and how many hours a day you wear it.

Try different brands of hearing aid battery to find which ones last longest for you.