What your battery health percentage is actually telling you

Your Mac says Service Recommended, or the battery figure on your Windows laptop has slipped a long way below where it started, and you want to know whether that means buying a battery or carrying on. Here is how we read those numbers at the bench.

What the percentage is comparing

The figure sets what the battery holds today against what it held when the laptop was new. It is not telling you how full the battery is at this moment, and a number that has drifted down over years of use is wear rather than a fault. The cycle count matters to us as much as the percentage does, so for a Mac we look the model up on Apple’s cycle count page, which gives the rating for each laptop and the capacity Apple designs a battery to still have when it reaches it.

Where we get the number from

On a Mac, macOS reports the battery condition itself, and Apple’s page on the Service Recommended message covers both where that sits and what Apple makes of third-party battery apps. We work from the macOS figure, because people do arrive with two apps giving two different answers. On Windows the machine can generate its own battery report, listed as the batteryreport option in Microsoft’s powercfg reference. We run one at the bench, compare what the battery holds at full charge now against what it was built to hold, then read the charge history underneath that.

What we check before blaming the battery

A laptop that dies at half charge is not always a battery. We try a known-good charger first, because a tired adapter or cable looks much the same from the outside as a tired cell. Then we measure the port and watch how the machine draws power, then we put the cycle count and the report side by side, then we load the machine up and watch what the charge does. A low percentage next to a low cycle count is not normal wear, so before we blame the cells we look harder at the charging side and at how the machine has been stored.

When replacing is worth it

The cases we see most are the laptop that shuts down the moment you unplug it, the one that has to stay plugged in to be useful, and the one where the case or the trackpad has started to lift. That last one we would rather you stopped using and brought in than left sitting in a bag. If the percentage is low but the laptop still gets you from one charge to the next, there is no rush to change anything.

Bring the charger in with the laptop, so nobody has to guess which half of the problem is which. Prices here are battery from $120, and diagnosis is free if the repair goes ahead, $90 to $100 if it does not. We offer no warranty of our own, and your Australian Consumer Law rights still apply. To get it looked at, call 0421 741 424.