Battery Health for Used Devices: A Template to Request Test Data from Sellers

Hook: Don’t buy a ticking time bomb — verify battery health first

Buying a used laptop, smartwatch, speaker or earbuds at a deep discount feels great—until the battery dies in days or needs a $150 replacement. As a value-first shopper in 2026, your biggest risk isn’t the screen scratch; it’s a degraded or misrepresented battery. This guide gives you ready-to-send templates, exact commands and step-by-step checks so sellers send verifiable battery health screenshots and test logs you can trust.

The new reality in 2026: Why battery verification matters more than ever

Late-2024 through 2025 saw marketplaces lean into refurbished and salvage channels. Regulators in Europe and parts of North America pushed stronger repair and diagnostics transparency, and manufacturers started offering more battery telemetry — but not consistently. That means buyers must still ask for evidence. In 2026, sellers can often produce useful logs, but platforms and privacy updates sometimes restrict raw telemetry. The result: you should expect screenshots plus short videos or exported reports from device tools.

What you should expect from a trustworthy seller

• Battery metrics: cycle count, full charge capacity (mAh), design capacity (mAh), health percentage, and (if available) internal resistance or voltage under load.
• Timestamps or short video: a dated screenshot or 10–30 second screen recording showing the report being produced.
• Device identifiers: model and serial number matching the listing and an image of the device’s About page or system settings.
• Test description: how the test was done (example: “full-charge then playback at 50% volume until 20% battery”).

How to ask — the central template (copy/paste)

Start with a short, polite request. Use this universal template, then pick the device-specific add-ons below.

Universal seller request template

Hi — I’m interested in the [device model]. Before I commit, could you please share verifiable battery health info? Please include:

1. a screenshot or exported battery report showing cycle count, full charge capacity and design capacity;
2. a short (10–30s) video or screenshot showing the exact command/app used to generate the report, with today’s date visible (or hold a handwritten note with today’s date next to the device);
3. an image of Settings → About (or the serial number label) so I can confirm it matches the listing.

If you can’t run the report, let me know and I’ll walk you through it. Thanks — [your name].

Device-specific instructions & templates

Below are short how-to steps for common device classes and ready-to-send text you can paste into a marketplace message.

Laptops (Windows)

Ask the seller to run the built-in battery report and send the HTML or screenshots plus a short video of the command line.

1. Open an elevated Command Prompt (Run as Administrator).
2. Type: powercfg /batteryreport /output "C:\\Users\\Public\\battery-report.html"
3. Open the generated battery-report.html, screenshot the Summary and the Recent Usage / Battery capacity history sections, and share the file if possible.

Hi — please run this and attach the HTML or screenshots: open an Administrator Command Prompt and enter: powercfg /batteryreport /output "C:\\Users\\Public\\battery-report.html". Send the generated report (Summary + Battery capacity history) and a short video of you running the command. Thanks.

Laptops (macOS)

macOS provides SPPowerDataType output. Ask for both the Settings > Battery screenshot and a Terminal output.

1. Open Terminal and run: system_profiler SPPowerDataType
2. Alternatively, capture: Apple menu → About This Mac → System Report → Power, and screenshot Cycle Count, Full Charge Capacity and Design Capacity.
3. For extra proof, run: ioreg -l | grep -i "maxcapacity\|currentcapacity\|cyclecount"

Hi — can you screenshot About → System Report → Power (Cycle Count + Battery Capacity) and paste the Terminal output for: system_profiler SPPowerDataType (or run ioreg -l | grep -i "maxcapacity\|currentcapacity\|cyclecount")? A short screen recording while you run the commands is great too.

Smartphones & Tablets (iOS and Android)

Smartphones often present battery health in Settings. If more detail is needed, apps like AccuBattery (Android) or iMazing (desktop) can export logs. ADB offers advanced options for Android.

• iOS: Settings → Battery → Battery Health & Charging — screenshot the Battery Health screen and Settings → General → About showing model/serial.
• Android: ask for Settings → Battery → Battery usage + a screenshot, and if comfortable, run adb shell dumpsys battery (requires enabling USB debugging) and paste the output.

Hi — please attach a screenshot of Settings → Battery → Battery Health (or Battery usage) and General → About. If you can run adb, please paste the output of: adb shell dumpsys battery. Thank you.

Smartwatches (Apple Watch, Wear OS)

Smartwatches expose limited battery telemetry on-device. Ask for companion app screenshots plus a short continuous-use test.

1. Apple Watch: open Watch app on paired iPhone → My Watch → Battery, screenshot Battery Health (if shown) and About on the paired iPhone.
2. Wear OS: open the watch’s Settings → Battery or the phone’s Wear OS app; for advanced users, use adb to pull batterystats logs from the watch (adb over Bluetooth/Wi‑Fi for devs).
3. Request a short 2–4 hour playback or workout test at specified settings (e.g., GPS on, notifications off) with timestamps: seller should report start and stop battery percentages.

Hi — can you send: 1) screenshot of the Watch app showing battery info and About/serial on the paired phone, and 2) a short test: start at 100% and run a 2‑hour workout or continuous music/playback, then send the ending battery percentage and timestamps. That’ll help me confirm real-world life. Thanks.

Bluetooth speakers, earbuds, and portable audio

Many speakers and earbuds report battery state in their companion apps. If no app exists, ask for a timed playback test at a fixed volume.

• Ask for companion app battery percentage and device firmware version screenshots.
• Request a recorded test: charge to 100%, play a playlist at 50% volume (specify a streaming source) and report remaining battery after 1 hour and 3 hours, plus a short video showing battery percentage at each checkpoint.

Hi — please show the companion app battery screen and firmware version. If the app doesn’t report capacity, please charge to 100%, play music at 50% volume from [source] and send a short video showing battery % at these checkpoints: start (100%), 1 hour, 3 hours (or until device shuts off). Thank you.

Power banks and batteries sold separately

For power banks, ask for a load test: full charge, then power a known load (phone or a USB load tester) and note the delivered mAh. Vendors should provide capacity rating and last charge cycle if known.

Please fully charge the power bank, then charge a phone or use a USB power meter and report the delivered mAh and starting/ending device battery levels. Also include photos of the label showing capacity (mAh) and any date code.

How to interpret the data sellers send

Focus on three numbers (where available):

• Design Capacity — factory-rated capacity in mAh.
• Full Charge Capacity (FCC) — current max charge in mAh.
• Cycle Count — how many full cycles the battery has gone through.

Calculate Health % = (FCC / Design Capacity) × 100. Example: Design 5000 mAh, FCC 3700 mAh → Health = 74% (meaning ~26% wear).

Benchmarks (practical thresholds)

• 90–100%: Excellent (expected for newer or lightly used devices)
• 80–89%: Good — acceptable for budget buys but expect reduced runtime
• 70–79%: Fair — consider negotiating price or budgeting for replacement
• <70%: Poor — replacement likely within a year. Avoid unless price reflects replacement cost.

Red flags that deserve a hard pass

• No screenshots or only a single edited image with no metadata.
• Cycle count that’s implausibly low for age (e.g., 10 cycles on a 3‑year device) or low cycles but very low FCC.
• Seller refuses a short video or to show the serial number matching the listing.
• Bulging battery, heat damage, or swollen case in photos.

Verification techniques — make screenshots harder to fake

Ask sellers to include one of these low-effort authenticity checks:

• Hold a handwritten note with your username and today’s date next to the device when taking the screenshot or recording the test.
• Include a short video showing the report being opened and saved. Video is harder to fake than static images.
• Request multiple screenshots from different app screens (About, Battery, System report) so edits are more obvious.
• Check image EXIF data if the platform allows image download — many edits strip EXIF but original phone photos retain a timestamp.

When the seller can’t run diagnostics — safe alternatives

Some sellers (especially of proprietary wearables) can’t extract full telemetry. In that case:

1. Request a standardized short live test (e.g., charge to 100% then play video/audio for 90 minutes at 50% volume and record start/end percentages).
2. Ask for clear images of the device’s physical battery label, if accessible, including date codes.
3. Ask about recent charging behavior: how often they charged, whether they used fast-charging, and if they ever replaced the battery.

Price negotiation: how to factor battery health into your offer

Use battery health as a bargaining chip. Practical rules:

• For laptops and phones, estimate a replacement battery cost (parts + labor). Subtract that from your target price, then add a buffer for shipping and risk.
• If health is 70–80%, request a discount of 10–25% depending on model and replacement cost.
• For speakers and earbuds, negotiate based on the test playback run‑down: if they lose >30% capacity vs expected, reduce offer.

Case study (real-world style example)

In late 2025, a buyer found a 2019 Ultrabook listed for $320 (retail $900 when new). The seller initially provided a photo of the About screen only. The buyer requested a powercfg battery report and a short video. The report showed 800 cycles and 58% health; the buyer negotiated to $230 and budgeted $120 for a replacement battery. The result: total cost still under $350 and the machine lasted another 4 years after battery replacement. Without the report, the buyer would have paid full listing price and faced a surprise >$120 repair.

2026 trends & future-proof advice

Expect these trends through 2026–2028:

• More marketplaces will integrate diagnostic attestation APIs that allow verified battery reports at listing time. When present, those listings should be prioritized.
• Right-to-repair laws in many regions require manufacturers to publish battery replacement guides and parts pricing; factor this into your negotiation and repair planning. See analysis of recent regional rules here.
• Battery chemistry advances (solid-state prototypes) may change replacement costs for newer models, but most used devices in the marketplace will still need Li-ion replacements for years.
• Privacy and telemetry restrictions may mean some sellers can only supply screenshots instead of raw logs — insist on video/signed date notes in that case.

Checklist: Quick buyer battery verification (copyable)

• Ask for battery report + short video or handwritten dated note.
• Confirm model and serial number match the listing.
• Calculate Health % and check cycle count vs device age.
• Run red-flag checks (bulging, mismatched metadata, seller refusal).
• Negotiate price based on replacement cost and wear level.

Extra: Advanced commands and tools (for power users)

• Windows: powercfg /batteryreport (HTML) — includes recent usage and capacity history.
• macOS: system_profiler SPPowerDataType and ioreg -l | grep -i capacity/cyclecount.
• Linux: upower -i $(upower -e | grep -i BAT) or read /sys/class/power_supply/BAT*/uevent.
• Android: adb shell dumpsys battery and adb shell dumpsys batterystats --charged (for developers).
• Apps: AccuBattery (Android), CoconutBattery (macOS, iOS companion), iMazing (desktop exports), manufacturer companion apps for earbuds and speakers.

Final actionable takeaways

• Always ask — don’t assume a low price is worth it without battery evidence.
• Prefer reports + video — static images alone are easy to fake.
• Calculate health % and compare with replacement cost before buying.
• Use the templates in this article to save time and sound professional.
• When in doubt, either negotiate a large discount or walk away; batteries are a hidden cost buyers often underestimate.

Call to action

If you found these templates helpful, copy the templates above and paste them into your next message to a seller. Join the faulty.online community or sign up for our free checklist pack to get printer-ready test sheets, video script prompts, and an editable message library that speeds verification. Protect your purchase — get the battery data you need before you pay.

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