All batteries gradually lose their capacity over time. This can affect older devices such as mobile music players. The solution is to replace the battery with a new one. Rather than send our third-generation iPod for repair we have found a replacement battery from Maplin that also comes with the tools needed to open up the iPod.

Before starting, make sure that you have the right kit for your iPod as different versions are different sizes. The other important point is that opening an iPod in this way will invalidate the warranty. An older device such as this may longer be in warranty anyway but it does mean that you won't get any free help if the iPod is broken. In the case of this iPod is wasn't covered anyway and replacing the battery was cheaper than buying a new device entirely.

Step 1. Removing the back case
There are no screws on the iPod case so opening it up is the hardest part of the process. The two tools supplied with the battery are used to prise open the case to reveal the three catches on each side.

Start about 60mm down from the top of the iPod, roughly in line with the four buttons on the front. Slip one of the tools between the plastic and metal sides of the iPod and pop the catch out. We ended up using a screwdriver.

Once the first catch is released it is much simpler to do the rest. Then the case can be opened out. But be careful because there is a cable that connects the two sides together. Don't pull it out.

Step 2. Removing the hard drive
The hard disk is surrounded by blue plastic. Lift the hard disk out and you can see the connector. Get your fingernail underneath the connector and lift it out. Put the hard disk on one side safely

Part 3. Removing the old battery
The battery is the large black square inside the iPod with a connector. Make a note of which way round the coloured wires are fitted on the connector. On our iPod the red cable was on the inside of the iPod and the white towards the outside.

Carefully remove this connector and look to see if the wire is routed underneath the circuit board. Lift the battery out. There may be some resistance as our battery was stuck down in place. Remove the cables from underneath the circuit board.

Don't throw the old battery away in normal rubbish. Your local tip should have a section for disposing of batteries.

Step 4. Insert the new battery
Tuck the cables for the new battery underneath the circuit board as the old ones were and the push the new battery down into place.

A little more force may be required as our new battery was slightly larger than the old one. Pop the connector in and it should click into place.

Make sure the cables are in the same order as the old battery and that the wires are tucked away so they won't get caught on anything.

Step 5 Reconnecting the hard drive
Carefully align the connector on the hard disk with the one on the iPod. It's best to start at a slight angle to match the top of the connector up and then you should be able to feel when it's in place and push it down in place. Gently lay the hard disk back down on top of the circuit board. Check the cables again.

Step 6 Putting the case back together
With the hard disk in place the final step is to put the halves together again. Be careful of the hold switch as the switch is on the circuit board but the physical switch is on the other side of the iPod. Align both so that the black switch falls in between the two red tabs.

The easiest way to do this is to make sure that they are both switched in the same direction. Bring the two halves together and push all the catches together on one side first and then move on to the other side. Also check that the hold switch is working properly.