Make your batteries last: the simple rules for phones and laptops

Ask any repair shop what they replace most, and it's batteries — the phone that dies by 3pm, the laptop that only works while plugged in. The part that's most expensive to replace is also the most mistreated: we leave phones charging all night in the sun, drain them to zero "to save the battery", and fry them with cheap chargers. Some quick, mostly-free rules can give any battery an extra year or three of life.

The 20–80 rule

Modern phone and laptop batteries (lithium-ion) are happiest in the middle. They hate two states: being fully empty and sitting at 100% for long periods. The practical version of this:

• Don't run it to zero. The "fully discharge to calibrate" advice is from the old nickel battery era — lithium batteries are damaged, not helped, by deep discharge.
• Unplug when you can, ideally before 100%. Keep a device plugged in at 100% all day is the second-biggest avoidable wear. Stopping at around 80% for daily use is the single biggest battery-extension habit that exists.

You don't need to be obsessive — a laptop that goes to 100% overnight sometimes is fine. It's the constant extremes, month after month, that kill batteries early.

Heat is the real killer

If the two enemies of a battery are full and empty, the bigger one is heat. Heat permanently damages lithium cells, and it's not about dramatic sun exposure:

• The phone has been charging while playing games on the bed in a blanket: that's cooking it.
• A cheap charger that runs hot: cooking it.
• Leaving the laptop closed and charging in a hot bag: cooking it.

Simple version: if the device feels hot to the touch, don't charge it and don't cover it. Charging at night on a bedside table, phone screen-down and uncovered, is the calm way.

Cheap chargers cost more than they save

The K50 "anything charger" is a false economy double: poor chargers deliver unstable power and heat that ages the battery, and some cheap "fast" chargers push a phone's battery dramatically harder while never reaching the advertised speed. Use the charger that came with the device or a reputable-brand one with the right wattage, especially for anything you'll own for years.

Two things that actually help

• Check your battery health once in a while. Most phones show battery health in Settings (often under Battery); laptops report it too on Windows with a built-in command — open Command Prompt and type powercfg /batteryreport, and Windows saves a report showing its true capacity. Knowing the real number stops you from being sold a dying device later.
• Keep good charge habits during load-shedding. A laptop is the lucky one here: it's a built-in UPS. Expecting the laptop to be a backup power source while running it fully, every day, does wear the battery — but it's exactly what the battery is for, and a replaceable laptop battery is cheaper than a unit. Use it, and remember the 20–80 rule when the power does come back.

What you should not bother with

Ignore "battery calibration apps", "battery savers" and overnight-optimisation magic. Battery health is physics, not an app. Also ignore the worried advice that charging overnight destroys batteries — modern phones manage their own charge at 100%, so the real overnight risk is only heat, not the act of charging.

The one-sentence rule

Keep devices between 20% and 80%, keep them cool, and use chargers that fit the device. That's the entire battery-care manual worth learning. Do that and you'll routinely get years of extra life out of devices — money saved that you can spend on something that actually matters. And by the way: the battery test is also the first thing to check when buying a used phone — batteries are the fastest tell of a device's true age.