Every iPhone battery wears out eventually — it's chemistry, not a defect. After two or three years of daily charging, the lithium-ion cell inside holds less and less of a charge, and at some point it starts causing real problems: short days, random shutdowns, heat, sometimes swelling. The good news is the signs are easy to spot once you know what to look for, and a battery swap is one of the quickest, lowest-cost repairs we do. Here are the four signs we tell customers to watch for — plus how to check your battery health yourself in about ten seconds.
Battery Life Drops Off a Cliff
The most obvious sign is a sudden drop in how long a charge lasts. If you're reaching for the charger twice a day when you used to make it to dinner, the cell is fading. You can confirm it yourself: go to Settings → Battery → Battery Health & Charging and check Maximum Capacity. When that number drifts toward 80%, or iOS shows a "Service" message, the battery is past its prime. That's the single most useful number to check before you bring a phone in.
It Runs Hot — Especially While Charging
A little warmth during gaming or charging is normal. A phone that gets genuinely hot sitting on the nightstand, or stays warm long after you unplug it, is not. An aging cell works harder and sheds that extra energy as heat, and heat speeds up the wear even more — a bad loop. If your iPhone is regularly hot to the touch, it's worth having it checked by an iPhone repair shop before the heat starts affecting the screen or board.
Random Shutdowns With Charge to Spare
If your iPhone dies at 30% or 40% — or shuts off the second you step outside in a New England winter — that's a classic worn-cell symptom. Old batteries can't hold steady voltage under load, so the phone cuts power to protect itself even though the meter says there's juice left. Cold weather makes it worse. If your phone keeps dying with charge on the gauge, the battery is almost always the culprit, not the software.
Swelling or a Lifting Screen
This one is urgent. If the screen is pushing up at the edges, the case won't sit flat, or you see a visible bulge, the battery is swelling — gas building up inside a failing lithium-ion cell. Stop charging it, power the phone down if you can, and bring it in right away. A swollen battery can crack the screen from the inside and, in rare cases, is a fire risk. Don't press on it and don't try to puncture or pry it out yourself.
Why iPhone Batteries Wear Out
Every lithium-ion battery has a limited number of charge cycles in it — roughly 500 full cycles before Apple considers a battery worn, which most people hit somewhere in the two-to-three-year range depending on how heavily they charge. Each cycle nudges the maximum capacity down a little. That's why a three-year-old iPhone that "won't hold a charge" usually isn't broken — it's just done its expected miles.
Heat is the accelerant. Charging in a hot car, gaming for hours, or leaving the phone in direct sun all age the cell faster. So does keeping it plugged in at 100% around the clock. None of this means you did anything wrong — it just means batteries are consumable parts, like tires, and swapping a tired one is routine.
New Battery, or a New Phone?
Sometimes a battery isn't the answer, and we'll tell you that. If your iPhone is genuinely old, slow across the board, and stuck on an iOS version it can't update past, a battery will improve the runtime but not the lag — at that point a new phone may be the smarter spend.
But for the vast majority of phones two to four years old, a battery replacement in the $79–$129 range is a fraction of the cost of a new iPhone and buys you another couple of years. The only way to know for sure is a diagnostic, which is why we run one free before recommending anything — it also rules out look-alike issues like a failing charging port or a board fault that a new battery wouldn't fix.
iPhone Battery Replacement at Fix 'N Repair
We replace iPhone batteries the same day for most models because we keep the common ones in stock — bring it in, we test it, and in many cases you wait while we swap it. Every replacement starts with a free diagnostic and comes with a 90-day warranty. Here's where pricing lands by model:
| iPhone Model | Battery Replacement |
|---|---|
| iPhone 17 series | $149–$159 |
| iPhone 16 / 16 Pro / 16 Pro Max | $119–$129 |
| iPhone 15 series | $109–$119 |
| iPhone 14 series | $109 |
| iPhone 12 & 13 series | $89–$99 |
| iPhone 11 / X / XR / XS / 8 / SE | $79 |
| iPhone 6 & 7 series | from $59 |
Prices are current as of June 2026 and exclude MA sales tax (6.25%) and the 3% card convenience fee. Battery costs shift over time, so call (857) 302-2655 or text us for the exact price on your model.
You can walk in to any of our four Massachusetts shops — Watertown, Newton, Burlington, and Wakefield. No appointment needed, and we'll always quote you before we start.
iPhone Battery FAQs
How do I check my iPhone's battery health?
Open Settings, tap Battery, then Battery Health & Charging. The Maximum Capacity figure shows how much charge your battery holds compared to when it was new. Once it drops toward 80% or you see a "Service" message, the battery is wearing out and a replacement is worth considering.
How much does an iPhone battery replacement cost?
At Fix 'N Repair, iPhone battery replacement starts at $59 for older models like the iPhone 6 and 7, runs $79 to $109 for the iPhone 11 through 15, and $119 to $159 for the newest iPhone 16 and 17 series. Prices don't include MA sales tax or the 3% card convenience fee. Call (857) 302-2655 for your exact model.
How long does an iPhone battery replacement take?
Most iPhone battery replacements are done the same day, and many while you wait, since we stock batteries for common models. Bring your phone in to any of our four Massachusetts locations and we'll run a free diagnostic first to confirm the battery is the real problem before we open anything up.
Is it safe to keep using a swollen iPhone battery?
No. A swollen battery is a lithium-ion cell building up gas, and continuing to charge or use it risks damaging the phone or, in rare cases, fire. Stop charging it, power the phone down if you can, and bring it in right away. We handle swollen batteries carefully and safely remove the old cell.
Will a new battery fix random shutdowns and slow performance?
Usually yes, when a worn battery is the cause. As cells age they can't hold steady voltage, so the phone shuts off or slows down to protect itself. A fresh battery restores that. Our free diagnostic confirms whether it's the battery or something else, like the charging port or board, before you pay for anything.
What warranty comes with a battery replacement?
iPhone battery replacements carry a 90-day warranty. Keep your receipt, since it's required for any warranty claim, and a texted or emailed receipt counts. Note that we can't warranty batteries or parts a customer supplies themselves. Call (857) 302-2655 with any warranty questions.
If two or three of these signs sound familiar, your battery has probably run its course — and that's an easy, affordable fix, not a reason to buy a new phone. Bring your iPhone in for a free diagnostic and we'll tell you straight whether a battery swap is worth it for your model.
Walk in to any Fix 'N Repair location for a free diagnostic and same-day battery replacement — 90-day warranty on every battery, transparent pricing, no appointment needed.
Call or text (857) 302-2655 See All iPhone Repairs