Most “the battery is dead” calls we get aren’t actually battery problems. Here’s how to tell what you’re dealing with before you commit to a swap.
The three signs that genuinely point to the battery
1. It runs for less than half what it used to, on the same workload
Open your laptop to the same browser tabs and apps you used a year ago. If a Mac or Windows machine that gave you 8 hours then gives you 3 now, that’s wear. Battery cells lose capacity gradually, usually 10–20% in the first two years, then accelerating. By year four most laptops are at half their original capacity.
On a Mac, hold Option and click the battery icon to see “Service Battery” or “Replace Soon” recommendations. On Windows, run powercfg /batteryreport in Command Prompt — it generates an HTML report showing design capacity vs full-charge capacity. If full-charge is below 60% of design, you’re at the point of diminishing returns.
2. The charge percentage jumps around
Plugged in at 80%, unplug, and it instantly drops to 40%. Or it sits at 100% all day, then dies in 20 minutes. That’s not how lithium-ion behaves when it’s healthy. The battery’s fuel gauge has lost calibration because the cells are no longer holding charge linearly.
Sometimes a few full discharge-and-charge cycles fix the gauge for a while. If it returns within a fortnight, the cells themselves are gone.
3. The case has bulged
If the trackpad clicks unevenly, the keyboard sits proud, or the bottom case isn’t flat against the desk anymore, the battery is swelling. This is non-negotiable — stop using the laptop, unplug it, and book a replacement. A swollen battery can rupture, and that’s the only kind of laptop fire we ever see.
The three things that look like battery problems but usually aren’t
It won’t charge at all
Far more often a charging-port issue (loose USB-C connector, snapped pin, lint inside the port), a dead charger, or a fault on the power IC than a dead battery. We’ll check the charger first — takes about a minute — before anyone touches the battery.
It dies under load
If your laptop powers off when you start a video call or compile code, but stays on while idle, the issue is usually the power-delivery circuitry on the motherboard, not the battery. The CPU asks for more current than the system can supply and the supervisor IC pulls the plug. Common on liquid-damaged or older laptops.
The charge LED is amber instead of white
On most laptops that means “charging” and is normal. White / green = fully charged. Different makes use different colour codes — check the manual before assuming.
What we do on the bench
Every battery diagnostic starts the same way: we read the battery’s reported design capacity vs current full-charge capacity, the cycle count, and whether the gauge is reporting any cell-level errors. That takes 10 minutes and gives us a hard answer instead of a guess.
If it’s a real wear-out, we fit an OEM-spec replacement and re-calibrate the gauge before sending it back. We use cells from the same suppliers as the original manufacturer where possible — never the £15 eBay packs that explode in headlines twice a year.
If it’s not the battery, we tell you and we don’t charge for the diagnostic. That’s the no-fix-no-fee bit.
When to replace, and when to live with it
Below 60% of original capacity, on a machine you use daily, replace it. The replacement pays for itself in less time wasted finding power outlets.
Above 80%, leave it alone. Heat and full discharge are what kill batteries faster than calendar age, so unplug when you’re at 80% if you can, keep the machine cool, and you’ll get another year or two out of it.
Battery diagnostic is free at our Bloomsbury bench — bring the laptop in, walk in any day. Or book online for free DPD pickup if you’re outside London.
