Caring for batteries in everyday gadgets

Most phones, laptops, tablets, earbuds and wearables use lithium-ion batteries, which lose capacity gradually through use, heat and the way they are charged. You cannot stop that wear completely, but you can slow it down by keeping batteries cool, avoiding long stretches at very high or very low charge, and replacing a battery once its decline begins to get in the way of normal use.

Battery wear is partly about time and partly about how many charge cycles a battery has been through. Each cycle wears it slightly, and the amount of charge it can hold falls over the years. The habits below do not reverse that process, but they reduce the stress that speeds it up.

How heat and charge levels affect wear

Heat is one of the main factors in battery aging. Leaving a phone on a car dashboard in direct sun, charging a laptop on a bed or under a pillow, or running a device hard in a warm room all raise the battery temperature. Higher temperatures speed up the chemical changes that reduce capacity. Charging also produces heat, so a device that feels warm while plugged in should move somewhere cooler. A thick case can trap that heat during fast charging.

Cold matters too, in a different way. Low temperatures reduce how much power a battery can deliver for a while, which can make a phone shut down in winter even though it still shows charge. Warming the device brings that capacity back. Avoid charging a lithium-ion battery in freezing conditions, because charging a cold battery can cause lasting damage. Let the device reach room temperature first.

The charge level a battery is held at also affects wear. A battery is under less strain in the middle of its range than when it is held at full charge for hours or drained close to empty for days. Keeping a device at 100 percent for long periods, or letting it sit near zero, usually shortens its useful life more than occasional extremes do.

Charging habits that slow wear

Many devices include a setting that limits charging to around 80 percent, or that holds the battery at a lower level overnight based on your routine. If your device offers either option, turn it on, especially for devices you leave plugged in for long periods. Look for it under the battery or charging settings.

Partial charges are fine. You do not need to let a lithium-ion battery run down before charging it, and frequent top-ups are generally easier on the battery than repeated full drains. The advice to drain a battery completely before recharging came from older battery chemistries and is not needed for the batteries in most everyday gadgets. Use a charger and cable that meet the device's specifications, because poor-quality accessories can deliver unstable power and generate extra heat.

Fast charging is convenient when you need power quickly, and occasional use is fine. Relying on it for every charge produces more heat than slower charging, so reserve it for times when the extra speed matters and use a slower charge overnight when you can.

When a device will sit unused for a month or more, charge it to around half, switch it off or leave it in its lowest power mode, and store it somewhere cool and dry. Check it every few months and top it up if needed. A battery left empty for a long time can drop into a state where it will not charge normally.

When a replacement makes sense

Many phones and laptops show battery health in their settings, which compares how much capacity remains with what the battery held when new. Replacement is worth considering when the device runs out much faster than it used to, shuts down unexpectedly at a charge level that previously worked, or needs to stay plugged in for ordinary use.

Compare the cost of a battery replacement with the cost of a new device and with how long you plan to keep the device. A replacement from the manufacturer or a qualified repair shop is often worthwhile on a device that is otherwise working well. Keep in mind that a new battery does not extend the period during which the manufacturer provides software updates.

Many small gadgets, such as earbuds and some wearables, have sealed batteries that cannot practically be replaced by the owner. For those devices, the choice is usually between a manufacturer service program, where one is offered, and a new device. Either way, recycle the old battery through a proper drop-off point when the device reaches the end of its life.

Before paying for a replacement, make sure the battery is really the cause. A slow or short-lived battery can also come from an app that drains power in the background, or from a software problem that a restart or update would fix. Check the battery usage screen in the settings to see which apps use the most power, and try the simple fixes first.

A swollen battery is a safety issue, not just a performance problem. Signs include a case that bulges or lifts, a device that no longer sits flat, a back panel that pushes out, or unusual heat or smell. Stop using and charging the device, keep it away from heat and flammable materials, and do not puncture, squeeze or try to open it. Take it to a battery recycling or hazardous-waste drop-off point, or follow the manufacturer's instructions for disposal. Batteries should never go into household bins.

A practical last step is to turn on the charge-limit or optimized-charging setting now, if the device offers one, and to write down the battery-health reading shown in its settings. That number becomes your baseline. Checking it again a year or two later shows how fast the battery is wearing, which tells you more than any guess about its age.