Why are the batteries in iPhones, Galaxies, and Pixel phones still so small?
Yesterday, I finished reviewing the RedMagic 11 Pro, a phone with a 7,500 mAh battery. This made me wonder. Why are the batteries in iPhones, Galaxies, and Pixel phones still so small?
This article may contain personal views and opinion from the author.
Yesterday, I finished reviewing the RedMagic 11 Pro, a phone with a 7,500 mAh battery. Unsurprisingly, this device now occupies the top of our battery benchmark table. This made me wonder. Why are the batteries in iPhones, Galaxies, and Pixel phones still so small?
Even the Galaxy S25 Ultra only packs a 5,000 mAh cell, and the battery capacity inside the iPhone 17 Pro Max is around this number as well. What gives? When Chinese phones are doubling the capacity of iPhone, Galaxy, and Pixel phone batteries, the latter seem stuck. I decided to do some digging.
Are thin phones the problem?
One might think that design considerations are the primary limitation for having huge batteries inside your regular iPhones and Galaxies. And it's true, to some extent. Especially with the recent push toward ultra-thin phones. The iPhone Air is just 5.6 mm thick, but its battery barely surpasses the 3,000 mAh mark.
On the other hand, the aforementioned RedMagic 11 Pro is around 8 mm thick and has a battery that's 2.5 times bigger than the Air. Plus wireless charging. It's a tradeoff I would make any day of the week.
Of course, Chinese phones now use silicon-carbon batteries, which have better energy density per volume, but before we delve into that, there's another reason why most companies outside China are stuck with small batteries, and it has something to do with regulations.
The 20 watt-hour limit
There are international transport regulations when it comes to batteries, and they are pretty strict. All lithium-ion batteries exceeding 20 watt-hours capacity (this translates to around 5,400 mAh) are classified as Class 9 dangerous goods.
The result? Significantly higher transport costs, specialized packaging, and a lot of paperwork are required to deal with phones featuring batteries with a capacity higher than 5,400 mAh.
But wait, how can Chinese manufacturers then ship around phones with 7,000+ mAh batteries? There's a workaround. Most of these brands, including OnePlus, Honor, Xiaomi, RedMagic, and more, used a stack of two batteries.
If neither of the individual cells exceeds the limit of 20 watt-hours, then the batteries fall into the "small lithium-ion battery" classification, and the taxes and paperwork are significantly lower.
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Samsung, Apple, and Google are slow to adopt this approach because it would require retooling and expensive changes at the production lines. Which brings us to the silicon-carbon angle.
What's a silicon-carbon battery?
We did a whole separate article explaining the tech, but long story short, it's a battery with high silicon content in its graphene anode. Silicon can store ten times more charged particles compared to lithium, so in theory, a battery with an anode from pure silicon will have ten times the capacity. But there are issues.
Silicon swells a lot when it stores energy, sometimes by as much as 300%. You can imagine what would happen if a smartphone battery suddenly expanded to three times its volume. It basically turns into a bomb inside your pocket.
Even if the silicon content is modest, let's say 10-15%, the swelling still occurs, and it can crack the anode and damage the battery irreparably.
There are workarounds to make the silicon-carbon anode stable, and these include various coatings and chemical mixtures and precise nanostructures to deal with stress and prevent cracking.
Chinese smartphone manufacturers are ahead on that front, mainly because of the looser regulations regarding batteries in the country. Honor is now well into the fourth generation of silicon-carbon tech, and the OnePlus 15 features one of the highest contents of silicon inside the graphene anode—15%.
When will we get silicon-carbon batteries in our iPhones and Galaxy devices?
The short answer is not soon. And the reason is… money. Samsung, Apple, and Google have invested billions in graphite-based conventional lithium-ion lines and switching to silicon-carbon would mean taking a massive financial hit.
Silicon-carbon batteries require different tools, new material sources to obtain high-purity silicon nanoparticles, and huge legislative work to obtain the necessary permits and certificates. That's a huge endeavor for a potentially small gain.
That's why the big three are trying to extend the life of traditional lithium-ion batteries as much as they can, optimizing the battery life quite aggressively sometimes. Speaking about software optimizations, there's another reason why silicon-carbon batteries won't be in your iPhone or Galaxy anytime soon.
Software and hardware integration
Silicon-carbon batteries require a completely different battery management system, with different voltage curves, degradation profiles, and charging behaviors. This brings along firmware changes, different charging chips, and even different thermal envelopes and packaging materials, so the cost rises even more.
When you add the Note 7 drama with devices catching fire and exploding, Samsung is extra careful about adopting new technology and pushing the battery capacity.
Apple, on the other hand, generally prefers to play it safe and at least internally test a big change for quite a long time before implementing it. So, does this mean iPhones, Galaxies, and Pixel phones will always suffer from small batteries and unimpressive battery life? There's hope.
What's next? When do we get 7,500 batteries in our iPhones?
So, Samsung, Apple, and the others will adopt the silicon-carbon tech in the end, but it will take time. Patience is key; don't expect the Galaxy S26 or the iPhone 18 to suddenly start packing 8,000 mAh cells.
According to the projections, the first improvements in capacity will be in the vicinity of 5-10%, so more like a 5,500 mAh battery in the next Galaxy Ultra, then probably 6,000 mAh a couple of generations down the iPhone Pro Max line, and so on.
Meanwhile, Chinese companies will most likely stay ahead, achieving high silicon content batteries in the next 5 years, so stay tuned for 10,000 mAh phones. They just won't read Apple or Samsung on the retail box.
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Mariyan, a tech enthusiast with a background in Nuclear Physics and Journalism, brings a unique perspective to PhoneArena. His childhood curiosity for gadgets evolved into a professional passion for technology, leading him to the role of Editor-in-Chief at PCWorld Bulgaria before joining PhoneArena. Mariyan's interests range from mainstream Android and iPhone debates to fringe technologies like graphene batteries and nanotechnology. Off-duty, he enjoys playing his electric guitar, practicing Japanese, and revisiting his love for video games and Haruki Murakami's works.
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