Phone Battery Guide: Health, Charging and Replacement

How phone batteries age

Almost every phone, tablet and laptop runs on a lithium-ion battery. These batteries are light and hold a lot of energy, but they're consumable parts. From the day your phone is made, the battery slowly loses its ability to hold a full charge, and no setting or habit can stop that completely. What you can do is slow it down.

Three things drive battery wear more than anything else:

• Charge cycles. A cycle is using the equivalent of a full battery's worth of charge, whether that's one full drain or several partial ones that add up. Each cycle wears the battery a tiny amount.
• Heat. High temperatures speed up the chemical changes inside the cell. Heat is the single biggest thing you can control.
• Sitting at the extremes. Spending long stretches at a completely full or completely empty charge stresses the battery more than staying somewhere in the middle.

Age matters too. A battery wears slowly even when it isn't used much, which is why a phone that has spent a long time in a drawer may not hold a charge well when you take it out.

Signs your battery is wearing out

Battery wear usually creeps up gradually, so it's easy to miss. Watch for these signs:

• You need to charge more than once a day for the same use you've always had.
• The phone shuts off suddenly, even with charge showing, especially in the cold or when using the camera.
• The percentage drops in jumps rather than smoothly.
• The phone feels slower than it used to, particularly opening apps or the camera.
• It runs warm during light use.
• Your phone shows a battery service message or recommendation.
• The screen is lifting, the back is bulging, or the phone no longer sits flat. This is a safety issue, covered below.

Not every battery complaint is the battery, though. A recent software update, an app misbehaving in the background or a weak cellular signal can all drain power quickly. Check your battery usage by app before deciding the battery itself is the problem.

How to check battery health

iPhone

1. Open Settings > Battery.
2. Tap Battery Health (called Battery Health & Charging on some models and iOS versions).
3. Check Maximum Capacity, which compares today's capacity with when the battery was new.
4. Read the Peak Performance Capability note. It tells you if iOS has limited performance to prevent shutdowns, or if service is recommended.

Newer iPhones also show the battery's cycle count. Our iPhone repair guide covers how batteries fit in with other common iPhone problems.

Samsung Galaxy

• Open the Samsung Members app and run the battery status test in its diagnostics section for a general read on battery condition.
• Check battery use by app in your battery settings, and use Device care (called Battery and device care on older software) to spot apps draining power.

See our Samsung Galaxy repair guide for more on Galaxy models.

Google Pixel

• On recent Pixel models, open Settings > Battery and look for Battery health, which shows an estimated capacity and whether the battery is in normal condition. Older Pixels don't show this screen.
• On any Pixel, Settings > Battery > Battery usage shows which apps are using the most power.

Whatever phone you have, treat the reading as a guide rather than a verdict. If the phone still gets you through the day comfortably, there's no rush to replace the battery.

Charging habits that actually help

You don't need to babysit your phone. A few easy habits make a real difference:

1. Charge whenever it's convenient. Lithium-ion batteries don't have a "memory". Topping up partway is fine and often better than a full drain.
2. Avoid running it flat regularly. An occasional empty battery won't hurt, but making a habit of it adds wear.
3. Turn on optimized or adaptive charging. Let the phone manage overnight charging for you (more on this below).
4. Keep it cool while charging. Don't charge under a pillow or on a bed, and avoid heavy gaming while plugged in.
5. Take off a thick case if the phone gets noticeably warm while fast charging or charging wirelessly.
6. Store it half charged. If you're putting a phone away for a long time, leave it at around half charge and power it off, rather than full or empty.

Common battery myths

Optimized and adaptive charging

All three major phone makers include settings to reduce wear from long periods at full charge:

• iPhone: in Settings > Battery, under the battery health or charging section, you'll find Optimized Battery Charging. It learns your routine and finishes charging just before you usually unplug. Recent models also offer a charge limit option.
• Samsung Galaxy: look for Battery protection in your battery settings. Depending on your software version, it offers options that stop charging before full or adapt to your routine.
• Google Pixel: look in Settings > Battery for Adaptive Charging and charging optimization options, which slow or limit charging overnight.

Leaving these on costs you almost nothing day to day. If you need a full charge before a long day out, most phones let you override them temporarily.

Heat and cold

Heat

Apple says iPhones are designed to work best in ambient temperatures between 0°C and 35°C, and the same general range applies to most phones. Above that, batteries wear faster and phones may dim the screen, slow down or stop charging to protect themselves. The most common culprits are a dashboard or seat in a parked car, direct sun at the beach or patio, charging under bedding, and gaming or navigating while charging.

If your phone gets hot, unplug it, take it out of its case and move it somewhere cool and shaded. Don't put it in the fridge or freezer. Sudden temperature changes can cause condensation inside.

Cold

Ontario winters are hard on batteries in a different way. Cold slows the chemistry inside the cell, so the phone can show less charge or shut off unexpectedly, even with a healthy battery. This is usually temporary, and the charge comes back as the phone warms up. An older, worn battery is much more likely to shut down in the cold.

• Keep your phone in an inside pocket rather than a bag or outer pocket.
• Let a cold phone warm up to room temperature before charging it. Charging a very cold battery is harder on it.
• If your phone shuts off outside, warm it up gently indoors before turning it back on.

Swollen batteries: what to do

As lithium-ion batteries age, get damaged or overheat, they can swell. It's not common, but it's the one battery problem you should never ignore.

Warning signs:

• The screen is lifting away from the frame or has a gap along one edge.
• The back of the phone is bulging or cracking without an obvious drop.
• The phone wobbles or spins when placed flat on a table.
• On a laptop, the trackpad is raised, stiff to click, or the case won't close evenly.

If the device is getting hot, smoking or hissing, move away from it and call 911.

Chargers and cables

A good charger doesn't need to be expensive, but it should be well made. Cheap, unbranded chargers and cables can overheat, charge erratically and, in rare cases, damage the phone's charging circuitry.

• Look for a certification mark. Chargers sold in Canada should carry a recognized safety mark such as CSA, cUL or cETL.
• Match the standard. Most recent phones use USB-C with USB Power Delivery for fast charging. Older iPhones use Lightning, and certified Lightning cables carry Apple's "Made for iPhone" approval.
• Replace damaged cables. Frayed ends, exposed wires or a plug that has to be held at an angle are reasons to retire a cable.
• Check the port, too. If charging is unreliable with several good cables, lint or a worn port may be the real problem. See our post on iPhone charging port fixes or our charging port repair page.

Wireless chargers are convenient, but they produce more heat than a cable. Line the phone up properly and remove thick cases or anything metal, such as a card holder, between the phone and the pad.

When to replace your battery

Replace the battery when it no longer fits your life, not when a number dips. It's time to book if:

• You can't get through a normal day without recharging.
• The phone shuts off unexpectedly or slows down noticeably.
• Your phone shows a service recommendation for the battery.
• There are any signs of swelling.

For many phones, a new battery makes an older phone feel much more usable, often for far less disruption than switching phones. If the phone has several other problems or no longer gets software updates, compare your options. Our post on repairing vs buying a new phone covers how to weigh it up.

What happens during a battery replacement

1. Back up your phone first, and make sure you know your passcode.
2. The technician opens the phone, removes the old battery safely and fits the new one.
3. The phone is closed up and checked for charging, battery readings and normal operation.
4. You test it together before she leaves.

On recent iPhones, a replaced battery may show a notice under Settings > General > About > Parts and Service History, and some battery details may display differently. Ask your technician what to expect for your model. Our battery replacement page has the details, and we also replace batteries through our iPhone repair, Samsung repair and Google Pixel repair services.

Tablets, laptops and consoles

The same rules apply to every device with a lithium-ion battery: keep it cool, avoid long stretches at empty or full, and take swelling seriously. iPads and tablets that no longer hold a charge can often get a new battery, as can many laptops. See iPad repair, tablet repair and computer repair.

Need a hand?

If your battery is draining fast, shutting down or starting to swell, a certified woman technician can replace it at your home, workplace, parked car or condo lobby. We cover Milton, Oakville, Burlington, Halton Hills, Mississauga, Brampton and Toronto. You'll get a free quote before any work starts. Call or WhatsApp (365) 351-4247, message us on WhatsApp, or book online. Our at-home repair guide explains how a visit works.

Frequently asked questions