Battery health is the single biggest factor affecting how long a used phone will actually work before needing replacement. A phone with 80% battery capacity left is fundamentally different from one at 50%, yet both might look identical on the shelf. Knowing how to test it, what to expect, and what it costs will save you from buying a dud.
Why Battery Health Matters for Used Phones
A used phone's battery degrades with every charge cycle. Unlike processors or screens, battery wear is irreversible—you can't fix it with software. When you buy refurbished, the battery health directly impacts real-world usage time. A one-year-old iPhone 13 with 85% battery capacity will comfortably last a full day; the same phone at 60% capacity might need charging by afternoon.
Battery health also affects resale value. If you plan to upgrade in two years, a phone starting at 80% health retains more value than one starting at 65%.
How to Test Battery Health Before Buying
iPhones
Apple makes this straightforward. Go to Settings > Battery > Battery Health & Charging. The percentage shown is what you need. Anything above 80% is considered acceptable by Apple's own standards; 85%+ is ideal for a used device. Some sellers include a screenshot in listings—ask for one if it's not provided.
Android Phones
Android doesn't have a built-in battery health display like iPhones, but you have options:
- Battery Info apps (AccuBattery, GSMArena Battery Info) give capacity readings, though accuracy varies
- USSD codes work on some Samsung and other Android brands; try
*#0228#for Samsung models - Developer mode access on some phones reveals battery data in system logs
- Manufacturer tools (Samsung SmartThings, for example) sometimes display battery health directly
The downside: these methods are less standardized than iPhone's built-in tool, so cross-check with the seller's documentation if available.
What Refurbishment Programs Test
Certified refurbished phones from major programs typically guarantee minimum battery health thresholds:
- Apple Refurbished: 80% minimum battery capacity
- Samsung Certified Refurbished: typically 80%+
- Amazon Renewed: varies by device, usually 80%+
- Carrier refurbished (Verizon, AT&T): often 85%+ for higher-grade units
Always check the listing—reputable sellers specify this. If they don't mention it, that's a red flag.
Typical Battery Health Ranges and What They Mean
| Battery Health | Real-World Impact | Grade | |---|---|---| | 90-100% | Full day+ on typical use; like new | Excellent | | 80-89% | Full day on moderate use | Good | | 70-79% | Full day if you're not heavy user; might need midday top-up | Fair | | 60-69% | Noticeable drain; second charger recommended | Poor | | Below 60% | Unreliable; consider replacement | Avoid |
Battery Replacement Costs and Timing
If you buy a used phone at lower battery health and it degrades further, replacement is an option:
- Apple iPhone: $70–$99 depending on model (out-of-warranty)
- Samsung Galaxy: $60–$100 typically
- Third-party repair shops: $40–$80, but quality varies
- DIY kits: $20–$40, but voids warranties and risks damage
Repair timelines usually run 3–7 business days at authorized centers.
Factor this in when negotiating price. A $300 phone at 65% battery health might cost $380+ once you budget a replacement battery.
What to Ask Sellers
Before committing:
- Request a current battery health screenshot (for iPhones especially)
- Ask how the phone was used (heavy gaming and constant charging degrades batteries faster)
- Confirm warranty coverage—does it include battery issues?
- Check if the device ships with original battery or a replacement
- Verify the phone's age; older devices often have older batteries already
Mercoly lets you compare and find trusted used and refurbished phone providers in one place, making it easier to verify seller credibility and warranty terms before purchase.
Frequently Asked Questions
Q: Can a used phone's battery health improve after sitting unused? No—battery health only declines or stays the same. Leaving a phone uncharged for months might show temporary capacity recovery, but true wear is permanent.
Q: Is a used phone with 75% battery health worth buying? It depends on price and use case; if you're getting a significant discount and don't mind midday charging or planning a battery replacement, yes. For a flagship phone, 80%+ is safer.
Q: Do battery health percentages differ between iPhone and Android tests? Yes—Android apps use different measurement methods, so an "85%" reading from one app might show differently in another. iPhone's official figure is the most reliable standard for comparison.
Start comparing battery health ratings and seller certifications today to find a used phone that actually lasts.