How Do I Know When to Replace My Smartphone Battery?

If you’re running out of power prematurely and aren’t ready to buy a new phone, it may be time

Edward C. Baig,

AARP

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Published December 23, 2025

AARP members and readers are invited to submit pressing technology questions they’d like me to tackle in my Tech Guru column, including issues around devices, security, social media and how all the puzzle pieces fit together. 

Running out of power is a common issue, as this question from a reader typifies.

I recently installed a software update on my phone, and now the battery doesn’t seem to hold a charge for very long. It peters out before the end of the day. Is this a sign that the battery needs to be replaced, or do I need a new phone instead? — Ruth L.

It’s not always easy to tell, Ruth, especially since you noticed your battery issues after installing a software update.

Many people, including me, share your frustration, though. We’re all too often convinced that Murphy’s Law will wreak havoc and our phone will run out of juice at precisely the worst possible moment: just ahead of a crucial call with bosses, customers, family members or caregivers, say.

But knowing when to replace the battery on the device, rather than replacing the phone itself, can be tricky.

Is something new much better than what you have?

One key factor is how close you are to trading in your handset anyway.

People are holding on to phones longer than ever nowadays — more than four years, in some instances. If your phone is otherwise humming along, the camera is performing fine and the screen and other parts of the device are mostly free of dings and scratches, then it may simply benefit from a fresh battery. Consider your current stage in the replacement cycle, and weigh the cost of a new phone against the expense of replacing a battery.    

You mentioned that you just installed a software update. If other funky things appear to be happening after doing that, it may be a sign that a new phone may indeed be in order.

Obviously, if you are seduced by a feature-rich new model that fits your budget or you anticipate one coming out soon, it doesn’t make much sense to spend on a battery now.

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You may well arrive at a different decision if your current phone is still under warranty and the cost of swapping out the battery is cheap or even free.

Limited lifespans

All rechargeable lithium-ion batteries have limited lifespans related to their chemical age. Under normal use and regular charging patterns, the original battery on a now two-year-old iPhone 15 model, for example, is designed to retain 80 percent of its capacity at 1,000 cycles, Apple says; on iPhone 14s, 80 percent capacity is achieved at 500 cycles. Over time, the ability of such batteries to hold a charge diminishes.

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According to Apple, a complete charge cycle occurs when you have discharged or used an amount that represents 100 percent of your battery’s capacity, but not necessarily all from a single charge.

Other factors can generally impact battery life, including overcharging or exposure to extreme temperatures.

Apple says most people can safely charge their iPhones at night even if the battery isn’t completely depleted. The phones are designed to stop charging when they reach full capacity, and resume when the battery level drops below 95 percent.

You can set charge limits on an iPhone by tapping Settings | Battery | Charging | Set Charge Limit. Another option found here is an Optimize Battery Charging switch that, when enabled, allows iPhones to wait to finish charging past 80 percent until the time you need to use it.

It’s a similar story on Android. You can choose a Basic setting on Samsung’s flagship Galaxy handsets so that it, too, stops charging at 100 percent and resumes at 95 percent. An alternate Maximum setting will stop charging at 80 percent. And an Adaptive setting uses Maximum when you sleep and switches to Basic before you wake up. Samsung says sleep time is estimated based on your phone usage patterns.

If you have an iPhone, you can check the overall status of your battery by tapping Settings | Battery | Battery Health. If the battery is functioning as expected, it’ll show up as Normal. You’ll also see Maximum Capacity expressed in percentage terms, described by Apple as a measure of battery capacity relative to when the device was new.

My 15 Pro Max was 82 percent at the time I wrote this column; trust me, I often felt it by the end of the workday.

Dropping below the 80 percent threshold is a sign that a replacement is in order. Under an AppleCare warranty plan, Apple will replace that battery for free. Apple’s tab to replace an out-of-warranty iPhone 15 Pro battery, like mine, is $99, and $89 for certain older models.

Under this Battery Health area in Settings, Apple also displays the battery’s cycle count, manufacturer date and first-use date.

You can similarly get a reading on your battery’s remaining capacity on Android phones. For example, Google Pixel users can tap Settings | Battery | Battery health | Battery capacity. Google also uses an 80 percent threshold, with the number of cycles varying by model.

On the Pixel, you can choose an Adaptive Charging option, which allows the phone to learn your charging patterns and pause at 80 percent. It then finishes charging to 100 percent an hour before you typically unplug. You can also choose an option where the phone will only charge up to 80 percent.

Samsung also allows you to choose a setting on its flagship Galaxy phones that will automatically cease charging at 80 percent.

Where to replace the battery?

If you decide to replace the battery but not the phone, there may be a retailer or repair shop nearby that can handle the transplant. If you’ve got an iPhone, you can visit an Apple Store or an authorized service provider. Android makers also work with authorized third-party service centers, and you can often initiate a repair at the manufacturer’s website.

Prominent retailers that handle battery replacements include Batteries Plus, Best Buy, Micro Center, Staples and uBreakiFix by Asurion. Local independent technicians are also worth considering, but be sure to check user reviews.

Most smartphones nowadays, including iPhones, Galaxys and Pixels, are not designed to have users replace the batteries themselves. Phones with user-swappable batteries were more common years ago.

Bonus tip: Steer your own Spotify music preferences

Spotify employs artificial intelligence to curate personalized playlists and surface music it thinks will appeal to its 713 million users worldwide. The streaming giant recently began testing a feature called Prompted Playlists, initially for premium subscribers in New Zealand, which the company says will not only passively learn your listening preferences but also let you steer and shape the algorithm in your own words.

Spotify suggests prompts with explicit instructions such as this: “Play music from my top artists for the last five years.” You might follow up with: “And feature deep cuts I haven’t heard yet.”

If the New Zealand test goes well, it’s reasonable to expect that Spotify will bring the feature to the U.S., although the company has not specified if or when.

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Edward C. Baig covers technology and other consumer topics. He previously worked for USA Today, BusinessWeek, U.S. News & World Report and Fortune, and is author of Macs for Dummies and coauthor of iPhone for Dummies and iPad for Dummies. Follow him on LinkedIn; Threads; and X, formerly known as Twitter.