Battery Health 101: What That Percentage Actually Means When Buying Refurbished

If you've shopped for a refurbished phone before, you've probably seen the term "battery health" thrown around a lot. It's one of the first things buyers ask us about, and for good reason — it's the single biggest factor in how a used or refurbished phone will actually feel to use day to day. Here's a plain-English guide to what it means and how to keep it in good shape.

What "battery health" actually measures

Every lithium-ion battery degrades a little each time it's charged and discharged. Battery health is a percentage that tells you how much capacity your battery still has compared to when it was brand new. A battery sitting at 100% health can still hold its full original charge. Drop to 85%, and it's holding roughly 85% of that original capacity — meaning shorter screen time between charges, and on older phones, occasional unexpected shutdowns under heavy load.

On iPhone, you'll find this under Settings > Battery > Battery Health & Charging. On most Samsung Galaxy phones, it's under Settings > Battery and device care > Battery > View additional battery details (or the Samsung Members app, which gives a more precise diagnostic).

What's a "good" number when buying refurbished?

Apple itself only flags a battery as needing service once it drops below 80% health. Most people won't notice a real difference in daily use until it dips into the low 80s. Anything from 85% and up should feel close to new. That's why at SmartGear we fit a brand new battery into a lot of our higher-mileage devices before they're listed — models like our iPhone SE 2020 and iPhone 7 Plus ship with a fresh battery rather than the original one, so you're starting back at 100% regardless of the phone's age.

If you're buying from anywhere other than a specialist refurbisher, it's worth asking the seller to show you the battery health reading before you pay — a quick photo of the settings screen takes ten seconds and tells you far more than the phone's age in years.

Five habits that slow battery wear

You can't stop a battery from aging, but you can slow it down noticeably with a few habits:

1. Avoid extremes. Keeping a phone permanently at 100% or letting it regularly drain to 0% both stress the battery more than sitting in the 20–80% range. Most modern phones have an "optimised charging" setting that learns your routine and slows the last bit of charging overnight — worth switching on if it isn't already.

2. Keep it cool. Heat is the biggest accelerant of battery wear, more so than charge cycles. Leaving a phone on a car dashboard in summer or charging it under a pillow does more long-term damage than almost any charging habit.

3. Use a charger that matches the phone's spec. Cheap, uncertified chargers can deliver inconsistent power that generates extra heat. A properly rated charger like a Belkin Mixit home charger is a small, inexpensive way to protect the battery you've got.

4. Don't chase 100% before every outing. Topping up from 40% to 70% is gentler on the battery than repeatedly cycling from empty to full.

5. Update your software. Both Apple and Samsung regularly ship battery and power-management improvements in system updates — it's a free way to squeeze more out of what you've got.

The bottom line

Battery health is a much better indicator of a refurbished phone's real-world condition than its release year. A three-year-old phone with a new battery will often outlast a one-year-old phone that's been charged carelessly. When you're comparing refurbished listings, always ask for the battery health figure — and if you want the certainty of starting from 100%, look for listings that specifically mention a new battery.