Battery replacement, explained

How to tell it is the battery

A lithium battery is a consumable. Every full charge cycle takes a little capacity off it, and after two or three years of daily use most phones are running on something like eighty percent of what they started with. The symptoms are consistent and you have probably already seen them: the percentage drops in jumps rather than smoothly, the phone shuts down in the cold or when the camera opens even though it says thirty percent, it warms up noticeably on the charger, and a full charge that used to last a day now lasts until mid-afternoon.

Most phones will show you a battery health figure in settings. Anything under about eighty percent is where the symptoms start, and the phone may also slow itself down to avoid shutting off, which people often mistake for the phone being old. Replace the battery and that throttling stops. If your battery health reads high but the phone still dies early, something else is drawing power, usually an app or a failing charging circuit, and we will say so rather than sell you a battery.

A swollen battery is a different conversation

If the back of the phone is lifting, the screen is being pushed up at one edge, or a tablet has developed a bulge, the battery has started to swell. That is a failing cell producing gas. It is not an emergency in the sense of being about to catch fire, but it can if it is punctured, crushed or charged hard, and it will only get worse. Stop charging it, do not press the bulge back down, do not leave it in a hot car, and bring it in as soon as you can. A swollen battery is removed carefully and disposed of properly, and the rest of the phone is usually fine once it is out. Please tell the counter it is swollen when you hand it over.

What happens on the bench

Modern phones are sealed, and the battery is glued in. A replacement means opening the phone, which on most models is done through the screen or the back glass with heat to soften the adhesive, disconnecting the old cell, releasing the adhesive pull-tabs or dissolving the glue, fitting the new cell, and resealing the phone with fresh adhesive so it closes the way it did before. On tablets the same job is larger and slower, because the panel is bigger and the battery is often held by adhesive along its whole length. On game handhelds like the Switch the battery is behind the back cover and is one of the quicker jobs we do.

We check the battery health reading before and after, so you can see the number go from whatever it was to a fresh cell, and we test that the phone charges, holds a charge overnight on the bench if you leave it, and does not run warm.

Cells and what "new" means

There is a real difference between a fresh, correctly specified cell and the cheapest one on the market, and it shows up as a battery that reads full for a month and then behaves like the old one. We fit cells rated to the original capacity, and the part and the labour are both covered, so if the new cell does not perform you bring the phone back to the counter that did the work.

On some recent models the phone pairs the battery to the board, and a replacement fitted anywhere other than the manufacturer shows a notice in settings that the battery is not recognised as genuine, or hides the health figure. The battery works normally; it is a message. We tell you on the models where that applies before we start.

How long it takes

On most common phones a battery replacement is well under an hour, and at our counters it is usually done while you shop. Tablets take longer because of the size of the panel that has to come off, so on those we will usually ask you to leave the device for a few hours. If the phone also has a cracked screen, the screen has to come off for the battery anyway, and doing both at once saves you the second trip.

Your data

A battery replacement does not touch storage. Everything on the phone stays where it is. As with any repair, if the phone is on its last legs and you have not backed it up lately, do it before you come in; it costs nothing and it means the worst case is an inconvenience.

What to bring

The phone, and the charger and cable you normally use if the problem is that it will not charge, so we can rule out the cable and the port before assuming the battery. No box or receipt needed. If the battery is swollen, carry the phone flat and tell the counter when you hand it over.

When a battery is not the answer

Sometimes a phone that dies early has a battery that is fine. A charging port full of lint charges slowly and never quite fills the cell. A background app can drain a full charge in hours. A failing charging circuit on the board shows the same symptoms as a worn cell. Because diagnosis is free, we check the obvious things first and tell you which of these it actually is, and if the battery is not the fault we will not replace it.