OnePlus 15 battery life tested — we can't believe it

For as long as I can remember testing the best phones — 17-plus years at this point — there hasn’t been a time when a flagship model lasted me more than a day of battery life. But that all changes with the OnePlus 15, and fundamentally speaking, it opens up a new era for all phones going forward.

This is a big deal, so much so that I haven’t seen battery life this good since the pre-smartphone days when I was still rocking a flip phone. Back then, it wasn’t unheard of to get several days of use from your handset.

While smartphones kept on getting big and more powerful, the battery tech didn’t keep up. That’s why most flagships to this day still require nightly charging.

Part of the reason why the OnePlus 15 is such a big deal is because it isn’t using a lithium-ion battery like most phones. Instead, the company has turned to a silicon-carbon battery that crams in more density without adding any unnecessary weight or thickness to the phone. Here’s the result from our OnePlus 15 battery test.

OnePlus 15 battery test: What you need to know

By now, I’m sure you’re well aware about battery capacities. Higher ones tend to mean longer battery life, but the downside is that they often increase the overall size of the phone. That’s why bigger phones like the iPhone 17 Pro Max and Galaxy S25 Ultra last much longer than their smaller counterparts. That’s the limitation of lithium-ion batteries.

The OnePlus 15 leverages a totally new battery — a 7,300 mAh carbon silicone dual cell battery, which on paper seems like a massive increase in capacity over the 5,000 mAh power packs found in many of the models in our best phone battery life list. This is made possible through OnePlus’ advanced Silicon NanoStack technology, which achieves greater energy density due to the 15% silicone content that’s incorporated into the anode.

What does this all mean? Quite simply, it’s a much more energy dense capacity that doesn’t require any additional size increase. Now just imagine how thin phones like the iPhone Air and Galaxy S25 Edge could’ve benefited from using this new battery tech.

OnePlus 15 battery test: Tom's Guide battery drain test

Just like all the phones that go through the Tom’s Guide testing lab, battery life is determined by manually setting a device's display to 150 nits and running a script that simulates normal web surfing over cellular connectivity until the phone runs out of power. These times are recorded and then averaged to give us the result.

The OnePlus 15 sets a new record on our test because of its 25 hours and 13 minutes result. That’s a staggering feat to achieve when I look at the gap against its closest flagship rivals, the iPhone 17 Pro Max and Galaxy S25 Ultra. Running the same exact battery drain test on them, the Galaxy S25 Ultra manages a time of 14 hours and 27 minutes — while the iPhone 17 Pro Max lasts longer at 17 hours and 54 minutes.

Although the previous OnePlus 13 shows a remarkable battery life time at 19 hours and 45 minutes, it was achieved using an older version of the test. I suspect that it would be more in line with the Galaxy S25 Ultra’s time if we retested that year-old phone. Either way, it proves that the efficiency of the OnePlus 15's Snapdragon 8 Elite Gen 5 silicon combined with this new battery tech results in a big boost to battery life performance.

OnePlus 15 battery test: real world results

Now, I’m not one to solely judge a phone’s battery life performance from a synthetic test. I put more value into the real world results I get from using a phone with my daily routine, which is why I’m utterly blown away by the OnePlus 15.

After a full day of using the phone, I found its battery capacity down to 68% right when my head was about to hit the pillow on my bed. This is an anomaly like no other because even the best phones I’ve tested rarely ever get more than 30% — so to find the OnePlus 15 at 68% after a day felt odd.

I convinced myself not to charge the OnePlus 15 overnight, choosing instead to gamble on another day’s use. By the time I finished up at work the next day, I thought the battery would be closer to being depleted — but it proved me wrong. This time, the OnePlus 15 was showing a battery level of 24% by the time my night was over. Again, I thought about charging it at this point, but I wanted to see exactly how much longer I could get out of it.

Once it got to 20%, that’s when the battery indicator finally turned to red. I kept on using the OnePlus 15 normally for several more hours until it finally got to 2%, where I finally decided to throw in the towel and recharge. What’s really crazy is the runtime: 2 days, 11 hours, and 5 minutes. That’s almost 2.5 days on a full charge, which could’ve been more considering that the phone didn’t go into any power saving mode — and how I had the screen resolution and refresh rate set to high.

OnePlus 15 battery test: Bottom line

Obviously, usage varies by person to person. I would classify myself as a power user because I enjoy putting in some time playing some of my favorite games, watching reels on TikTok and Instagram, recording videos of the many best electric cars I get to test, and all of the apps I use.

The OnePlus 15 doesn’t just have the best phone battery life, but it’s also quite speedy at recharging courtesy of its 80W SUPERVOOC wired charging. Even though my own testing showed it peaking at 65W, the phone was still able to get the battery to 81% with 30 minutes of charging. All of this changes my perception that I can count on a phone to give me more than a couple days of use with a single charge.

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