How to know when it's time to replace the battery on your phone

Which? research has revealed that deteriorating batteries are often the most common fault affecting smartphones. But batteries are usually the cheapest part of a phone to replace and can be the easiest way to delay your next pricey upgrade.

Read on to find out if a new battery can breath new life into your phone, and discover some tricks to lengthening its life.

Our guide to the best smartphones to buy in 2025 reveals the models that aced our lab tests. 

Step 1: How to check your phone's battery integrity

Battery capacities naturally deteriorate over time and checking your phone's battery integrity percentage will tell you if replacing it might improve battery life. The lower the percentage, the lower the battery's capacity. 

It only takes a couple of seconds to see if your phone's battery is struggling to keep up like it used to. It's generally recommended that a battery capacity of 80% or more is healthy.

How to check your battery health on iPhones

Go to Settings > Battery > Battery Health and Charging. Here you can see the current maximum capacity of your battery and a few more useful settings worth looking at. 

How to check your battery health on Android phones

It's not as straightforward with Android phones, since different manufacturers have a slightly different setup. Samsung users can check battery health through the phone diagnostics on the Samsung Members app. Free third party apps like Accubattery, downloadable from the Google Play store, can also be a quick and easy way to check battery health.

​Should you replace the battery on your phone?​​​​

Most manufacturers say that a phone battery is worth replacing when its integrity drops below 80%. Some (such as Apple) will replace it for free under their warranties if it drops this low before it's a year old. But most batteries don't worsen drastically until they are much older and they are usually inexpensive to replace. This delays the need to buy a new phone and is a more environmentally-friendly choice.

However, before buying a replacement battery, weigh up how old your phone is and when software support will end. We don't recommend you continue to use a device for long without the security updates that keep your data safe – our phone support calculator effectively gives you a 'best before' date for your device. If this date is coming up in the next year, we'd generally recommend you consider upgrading instead of replacing your current phone's battery.

It's also worth bearing in mind that other factors can shorten your phone's battery life beyond your control. Software updates sometimes deliver new features that require more power to work efficiently.

You don't have to buy a flagship phone for £700 or more to get a real performer – our mobile phone reviews reveal Best Buys from just £340, and Great Value phones for as little as £130. You can also check our guides to the best iPhone deals and best Android phone deals for a bargain on a new handset.

How long should a new smartphone battery last?

Manufacturers generally say that a battery should not drop below 80% health until you've hit at least 500 full charges (i.e. from 0% to 100%), and many do better for longer. For most people this would equate to at least a couple of years, so if you plan to keep the phone for this amount of time, replacing the battery can put it back in tip-top shape for the duration.

How much do mobile phone battery replacements cost?

This can vary depending on two factors: who you buy the new battery from and which model of phone you have. You can get the battery replaced directly from your phone's manufacturer, or through to a reputable third-party retailer (such as Fixfactor, iSmash, Square Repair or Timpson).

For example, an official Apple battery replacement for an iPhone 12 will cost an estimated £85, and a more recent iPhone 14 is £95. But third party retailer iSmash will charge just £49 for these.

But buying the manufacturer's direct repair isn't always more expensive. Samsung Repair charge £69 for a new Samsung Galaxy S22 battery and Square Repair charge £80. 

Before buying, double check that the cost of the battery includes a professional installation. For example, OnePlus sells reasonably-priced replacement batteries for its devices, such as the Nord 3 5G battery for £42.65, but you'd have to fit it yourself or pay extra for a professional fit. We explain more in our guide to Mobile phone repair: How to fix your smartphone

Prices correct in April 2025.

Four quick tips to boost battery life on a mobile phone

There are ways to boost battery life without shelling out for a new phone or a new battery. Try these first to see if it helps. You can find more tricks in our guide on 9 easy ways to improve battery life on iPhone and Android

1. Enable battery saving mode

You've likely seen a request pop up on your phone to enable battery saving (or low power) mode once it's only got 20% of battery left. This mode limits certain features that are usually happening in the background that can drain your battery. But you can enable battery saving mode when you have more than 20% battery left in your phone's settings. In terms of general day to day use, you may not even notice a difference in performance, but your battery life will thank you.

In the settings on some phones, you can see how much battery life each of your apps are using and get access to other useful battery-related controls. If you have any particularly power-hungry apps, make sure to close them properly when you exit them as this limits how much the app will refresh in the background.

2. Change your screen settings

Some of the latest premium smartphones have screens that can get incredibly bright, which can have a big impact on the battery life. In our typical use testing, one of the most recent iPhones saw a boost of more than 15 hours in battery life just by decreasing the screen brightness to a medium level. So decrease it when you can.

There are other screen settings that might help too, such as enabling dark mode or shortening how long your phone's screen stays on when you're not using it (called screen timeout). Turn off the 'Always-On' function if your phone offers this, too.

3. Invest in a power bank

A power bank is a handy portable charger that can keep your phone's battery full of juice when you're on the go. See which models impressed in our tests of the best power banks and portable chargers.

4. Invest in a fast charger

Every phone has a different wattage limit when it comes to charging, and the higher the wattage, the quicker it charges. A number of us end up using standard 10 watt chargers when on average most phones can handle 20 to 30 watts. We've even tested some with a limit closer to 120 watts that go from 0% to 100% in under 20 minutes. So it's worth checking your phone's capacity and buying the quickest charger possible – see our guide to fast chargers for more. 

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