How to Test if Your Phone Battery Is Bad (iPhone & Android)
Your phone dies too fast. Is it actually the battery, or a software issue? Here are 5 tests you can run at home that give a definitive answer — no repair shop visit needed until you know.
Test 1: iPhone Battery Health (30 seconds)
The gold standard for iPhone diagnosis. Settings → Battery → Battery Health & Charging.
Read the Maximum Capacity percentage:
- 100% - 90% — Excellent. Battery is fine. Slowdowns are software.
- 89% - 80% — Aging. Some capacity loss normal. Replace if the phone is 3+ years old and you use it heavily.
- Below 80% — Past Apple's rated life. iOS throttles CPU performance to prevent shutdowns. Replace for immediate speedup.
- "Service" or "Significantly degraded" — Battery is failing. Replace within a week to avoid random shutdowns and possible swelling.
iPhone 15 and later also show Cycle Count. Above 500 cycles = past manufacturer rating.
Test 2: Samsung Galaxy hidden diagnostics (1 minute)
Dial *#0228# on the phone keypad. A hidden battery service menu opens showing:
- ASOC (Available State of Charge) — 100 is a new battery. Below 80 = significant degradation.
- Temperature — Should be near ambient at idle. Above 35°C at rest = battery working hard due to internal issues.
- Voltage — Nominal is 3.7-4.2V. Values far outside indicate failing cell chemistry.
Alternative: Samsung Members app → Diagnostics → Battery. Gives a simple pass/fail with a health percentage.
Test 3: Discharge curve test (30 minutes)
Measures how much charge the battery loses under a known load. Works on any phone.
- Charge to 100%, unplug.
- Note battery percentage.
- Play a 30-minute HD YouTube video at 50% brightness, WiFi on, screen on the whole time.
- Note battery percentage after 30 minutes.
Results:
- 7-12% drop — Normal for a healthy battery.
- 13-20% drop — Mild degradation.
- 21-35% drop — Significant degradation. Battery is aging.
- Over 35% drop — Battery is failing. Replace.
- Phone shuts off before 30 minutes — Battery cannot maintain voltage under load. Immediate replacement.
Test 4: Random-shutdown test
A healthy battery discharges smoothly and predictably. A failing one drops voltage suddenly when demand spikes, causing random shutoffs even at 30-50% remaining. To test:
- Charge to 60%.
- Open the camera app and record a 4K video for 5 minutes.
- Then immediately open the flashlight and leave it on for 2 minutes.
If the phone reboots or shuts off during this test, the battery cannot maintain voltage under peak load. Replace it.
Test 5: Physical inspection (60 seconds)
Some battery failures are visible from the outside. Check for:
- Bulging back cover — Slight raised area under the case. Point a flashlight along the edge; look for lifted glass or plastic.
- Rocking on a flat surface — Place the phone screen-up on a table. Push down on each corner. If it rocks like a see-saw, the battery is swelling from underneath.
- Screen separation — Look at where the display meets the metal or plastic frame. Any visible gap = swollen battery pushing the display out.
- Warmth at idle — Feel the back of the phone when it has been sitting doing nothing for 10 minutes. Warm = internal battery issue.
If any physical sign is present, stop using the phone. A swollen lithium-ion battery can rupture and ignite. Get it replaced within days.
Which test should you trust most?
- iPhone owners: Battery Health is the single most accurate readout. Trust it.
- Samsung owners: Combine *#0228# ASOC number with the discharge curve test for full confidence.
- All phones: Physical inspection is always the first check. A swollen battery makes the other tests moot — replace immediately.
Battery replacement cost in Canada 2026
- iPhone 11-14 — CAD $79 to $119
- iPhone 15-16 — CAD $109 to $139
- Samsung Galaxy S22-S24 — CAD $89 to $139
- Google Pixel 6-9 — CAD $89 to $149
- iPad (all) — CAD $99 to $169
- MacBook Air/Pro — CAD $179 to $279
If you tested and confirmed the battery is bad, book a doorstep replacement in Eastern Ontario. Book online or call +1-438-462-3477. Most replacements done in 30-45 minutes on site, 30-day warranty.
Frequently Asked Questions
How do I check iPhone Battery Health?
Settings → Battery → Battery Health & Charging. The Maximum Capacity percentage is the key number. 100% is a brand-new battery. Below 80% means the battery is past Apple's rated life and should be replaced. If it shows 'Service' or 'Significantly degraded', replacement is urgent.
How do I check Samsung Galaxy battery health?
Dial *#0228# on the phone keypad to open Samsung's hidden battery diagnostics. Look at 'ASOC' (Available State of Charge) — 100 is new, below 80 indicates significant degradation. Alternative: use Samsung Members app → Diagnostics → Battery. Both give similar results.
What is a battery cycle count and does it matter?
A cycle equals one full 0% to 100% charge (which can happen over multiple partial charges — two 50% charges equal one cycle). iPhone batteries are rated for 500 cycles before dropping to 80% capacity. iPhone 15 and later track cycle count in Settings → Battery → Battery Health. Samsung phones do not display cycle count directly.
Can I test the phone battery without opening the phone?
Yes — most tests are software-based and non-invasive. iPhone Battery Health, Samsung diagnostics code, and the discharge-curve test (measuring how fast the phone drains under known load) all give reliable results without disassembly. Only rule out physical swelling by feeling the back of the phone for lumps or seeing if it rocks on a flat surface.
How much does phone battery replacement cost in Canada?
iPhone: CAD $79 to $139 at independent shops, $109 to $149 at Apple Store. Samsung Galaxy: CAD $79 to $149 depending on model. Google Pixel: CAD $89 to $149. Most doorstep and in-store replacements take 30 to 60 minutes.
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