Apple recommend battery replacement when the battery health percentage falls below 80% across all its devices, and will display “Service Battery” when this happens. On Windows laptops, it is not so easy to determine the battery percentage and there may not be any warning the battery needs to be replaced. However, your battery should last between 3 and 10 hours from a charge depending on the model.
Windows
Microsoft provides a tool to generate a Battery Health web page by running powercfg /batteryreport and then you can open the file it creates in your web browser.
Once you have opened the web page, scroll to “Battery capacity history” and with a calculator divide the full charge capacity of the most recent date with the design capacity and then multiply that number by 100 to get the percentage.
For example, my laptop battery design capacity is 44,988mWh and if it had degraded to 35,000mWh, the percentage would be 76%
Apple MacBook
Since Ventura, Apple has provided a Battery section of Settings for this purpose. By default, it will show whether the battery is in the Normal range or whether the battery needs to be serviced. You need to click on the i icon to get more details for the actual percentage, which is recorded as Maximum Capacity.
In older operating systems, you can find these details from System Information from the Apple menu and in the Power section.
Apple also uses the cycle count of the battery to record how many times the battery has been recharged. A modern laptop has a battery that is designed to be cycled 1,000 times but earlier models (pre-2010) have batteries with much shorter cycle times (500-800)
Android phones and tablets
For completeness, Android phones and tablets you can check the battery health from Settings and then Battery.
Apple iPhone, iPad and Watch
Equally, Apple iPhone, iPad and Watch you can find the battery health from Settings then Battery then Battery Health & Charging for the Maximum Capacity.
