The iPhone 12 launched in 2020, which means a lot of them are now six years into their original battery. If yours hits 20% by mid-afternoon, or dies at 30% when it's cold out, the battery is the usual suspect. And it's cheap to fix compared to almost anything else on this phone.
Check if it's really the battery
Go to Settings > Battery > Battery Health & Charging. Two lines matter: Maximum Capacity and Peak Performance Capability.
| What you see | What it means |
|---|---|
| 90% or higher | Battery's fine. Look at apps, screen brightness or a weak signal instead |
| 80% – 89% | Getting tired. You'll feel it on long days |
| Under 80% | Worn out. Apple treats this as due for service |
| Performance management applied | Your phone shut down unexpectedly and iOS is now holding back peak speed to avoid it |
Don't go looking for a cycle count in Settings. That screen only arrived with the iPhone 15. On an iPhone 12, Maximum Capacity is your best built-in clue.
When the battery is weak, Apple says iOS can limit peak performance. That can look like slower app launches, choppy scrolling, a dimmer screen, lower speaker volume, or in extreme cases a camera flash that won't fire. Call quality, photos and GPS aren't affected. So if your phone feels slow and the battery is under 80%, the battery may be the whole story.
What it costs
| Where | Price | The deal |
|---|---|---|
| Apple | $89 | Genuine battery, done by Apple |
| Apple with AppleCare+ | $0 | Once health is under 80% |
| Independent shop | $69 – $109 | Fast, often same day. Battery quality varies |
| DIY kit | Cheapest | Strong adhesive, fragile cables. Not a first-timer project |
Battery or new phone? The quick math
Say your iPhone 12 is otherwise fine. Screen works, Face ID works, no water damage. A new battery for $89 makes it feel close to new on battery life again. A new phone costs hundreds. That's not a hard call. Swap the battery.
It gets closer when two things are wrong at once. A cracked screen plus a dead battery at Apple is $279 + $89 = $368. At a shop, an aftermarket OLED screen ($100 to $170) plus a battery ($69 to $109) runs about $169 to $279. That's still a lot less than a newer phone, and our iPhone 12 screen cost guide walks through which screen to pick.
Another point in the iPhone 12's favor: Apple's iOS 27 still supports it, so you keep getting updates. You won't get Apple Intelligence features, which need an iPhone 15 Pro or newer. If that's the thing you really want, a battery won't fix it.
When a battery won't save it
- Water damage. The iPhone 12 is rated IP68 (up to 6 meters for 30 minutes), but Apple says that resistance fades with normal wear, and liquid damage isn't covered by warranty. A phone that went for a swim can have problems a battery won't touch.
- A swollen battery. If the screen is lifting away from the frame, stop charging it and get it looked at right away. Don't press it back down.
- No sound on calls. Apple ran a free service program for iPhone 12 and 12 Pro units made between October 2020 and April 2021 with earpiece problems. It covered phones for 3 years after first sale, so by now that window has closed for basically every phone.
Make the new battery last
- Turn on Optimized Battery Charging under Battery Health & Charging. It waits to finish charging past 80% until you usually unplug.
- Keep it out of hot cars and off the dashboard. Heat ages batteries faster than anything else.
- Topping up during the day is fine. You don't need to run it to zero.
What to ask a shop
- Is the battery new, and who makes it?
- What's the warranty, and does it cover capacity dropping fast?
- Will you replace the adhesive so the phone keeps its seal as well as possible?
The verdict
If your iPhone 12 battery health is under about 85% and nothing else is broken, replace it. $89 at Apple, or a bit less at a good shop, buys you another couple of years on a phone that still gets updates. Skip it only if the phone has bigger problems or you're already set on upgrading.
Every iPhone 12 price is on the iPhone 12 page. Apple prices checked October 14, 2026. Shop prices are typical US ranges.
