Will my iPhone be faster after a new battery?

If iOS was throttling performance because of an aged battery (Settings, Battery, Battery Health may mention "Peak Performance Capability"), then yes, noticeably. Throttling is removed the moment a healthy battery is detected.

Is it safe to use a swollen battery for a few more weeks?

No. A swollen lithium-ion cell is unstable and can rupture. Bring it in. Same-day swollen battery removal is one of our most common emergency jobs.

How long does an iPhone battery normally last?

Apple's stated design target is "80% capacity at 500 complete charge cycles". For typical use, that works out to about 2 to 3 years before health drops materially. Heavy users hit it sooner. Light users keep their original battery for 4+ years.

Can I do it myself with a kit from Amazon?

Technically yes. In practice, you'll spend an evening cursing at the screen adhesive, probably nick a flex cable, and end up bringing both pieces to us. The savings vs a professional replacement are minimal once you factor in the kit, the time, and the risk.

My phone is the only thing I have. Can you do it while I wait?

Yes. Walk in with an appointment and you'll have it back in about an hour. Book a slot →

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iPhone Battery Health: When to Replace (2026 Guide) · The Repair Lab

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iPhone Battery Health Below 80%? Here's When It's Worth Replacing

At what battery health percentage should you swap your iPhone's battery? The honest answer, plus the symptoms that mean don't wait.

The Repair Lab Team4 June 20265 min read

iPhone battery health and when to replace, from a Birmingham repair lab

Open Settings, Battery, Battery Health & Charging. There it is: a percentage. Sometimes 99%, sometimes 73%. What does it actually mean, and at what point should you stop reading articles and book the swap?

This is the same call we help customers make every day at our Birmingham lab. Here's the framework.

What "Maximum Capacity" actually means

That percentage compares your battery's current full-charge capacity to its capacity when it was brand new. A reading of 85% means a fully charged battery holds 85% of the energy a new one did. It does not mean you have 85% of a battery's worth of charge in there right now. It's a measure of long-term degradation.

It also doesn't always update in real time. iOS re-estimates the figure based on actual usage cycles, so it can sit on a number for weeks and then drop by 1 or 2% overnight. Don't panic at a sudden change.

The 80% threshold. What Apple actually says

Apple's official guidance is straightforward. A battery is considered to be operating normally until it has retained at least 80% of its original capacity. Below that, iOS may start showing a Service or Important Battery Message warning, and Apple recommends replacement.

That's a fairly conservative number. We see plenty of phones still doing a full day at 78%, and plenty struggling to make it past lunch at 84%. The percentage is a guide, not a verdict. Your daily experience matters more.

When you should book the replacement, regardless of the number

Don't wait if any of these are happening.

Unexpected shutdowns. Phone says it's at 30%, drops to 1%, then dies. On the charger it bounces back to 30%. Classic ageing-battery behaviour. iOS may start throttling performance to prevent it, and you'll feel that as a slower phone.
You can't get through a full day on a charge when you used to.
The battery is swollen. Symptoms: screen starts lifting from the frame, glass back has popped a corner, the phone rocks when laid flat on a table. This is urgent. A swollen lithium-ion cell can fail catastrophically. Don't ignore it. Don't charge it. Bring it to us.
Charge speed has plummeted. A healthy iPhone with a fast charger should hit roughly 50% in about half an hour. If yours is crawling, the battery's internal resistance has gone up.
The phone gets noticeably hot doing nothing. Could be a runaway app, but a degraded battery often runs warm at idle.

When it's probably fine to wait

Battery health 82 to 85%, no other symptoms, you charge once a day before bed. No urgency.
One-off "battery health dropped from 89% to 88% in a week". Totally normal, iOS recalibrates.