Samsung's 1,200-cycle battery rating does not settle the silicon-carbon question

In the space of two days this week, Honor put a 7.76mm mid-range phone on its Eurasian site with an 8,560mAh battery inside it, and vivo confirmed that the V80 Lite will ship with a flat 10,000mAh. Neither is a flagship. Neither costs much. The Honor Turbo runs a Snapdragon 6 Gen 4 and lists for about RUB 36,990 in Russia — roughly $447 — with 80W wired charging and no wireless at all.

Five years ago those capacities would have described a power bank. Silicon-carbon cell chemistry got them into a chassis thinner than most flagships. And yet the battery number that generated the most argument this month was not a capacity figure at all. It was a cycle count published in a European regulatory database.

Under the EU's energy-labelling rules, manufacturers now have to declare to the EPREL database how many full charge cycles a phone's battery survives before it falls below 80% of its original capacity. The label uses 80% as its defined end point, and EU ecodesign rules require new smartphones to manage at least 800 cycles before reaching it.

Android Authority pulled the entries for Samsung's newest foldables and found all three — Galaxy Z Fold 8, Z Fold 8 Ultra and Z Flip 8 — rated at 1,200 cycles. The Galaxy Z Fold 7 and Galaxy S25 were rated at 2,000. The obvious culprit was equally new: these are the first Samsung foldables to use silicon-carbon cells.

Tech commentator Shane Craig went looking for the rest of the picture and found it doesn't hold together. He points to the EPREL listing for the Galaxy S26 Ultra, model SM-S948 — a phone with no silicon-carbon in it — which is also rated at 1,200 cycles, down from the S25's 2,000. Same drop, different chemistry. His own suspicion is heat from faster charging: the S26 Ultra moved from 45W to 60W, the Fold from 25W to 45W. But he is careful not to sell that as an answer, noting that the Flip 8 took the identical hit without charging any faster than its predecessor. His summary of what buyers should take from the headline is blunter than the headline itself: Samsung is still rated above rivals at 1,200 cycles, where Pixel and iPhone models have historically been declared at 1,000, and you cannot draw a straight line from that number to silicon-carbon without information nobody outside these companies currently has.

The reason Apple, Google and Samsung moved so slowly here has been the subject of a lot of speculation, most of it about supply volume. Marques Brownlee reported a different explanation, sourced from industry contacts at multiple phone makers who independently raised the same concern with him: swelling.

Silicon holds far more energy than graphite, which is the entire point. It also expands when it takes on lithium ions. "The silicon can expand to three times its original volume," Brownlee said, describing a cell that inflates and deflates on every cycle. The carbon in the name is there to absorb that movement, and the silicon is finely ground rather than solid to spread the mechanical stress — but the higher the silicon percentage, the closer to the limit. He was told some devices ship with a literal steel cage around the cell to contain it.

The scale problem is what keeps the big three cautious. Brownlee's source framed an acceptable defect rate as something under one in 250,000. "But at Samsung's or Apple's scale, if it's tens of millions of phones, that could still not be good enough," he said. "That could still be a dozen exploding Note 7s like it was in 2016."

There is one recent dataset on charging habits worth putting against all this. HTX Studio split six iPhone 12 units into fast- and slow-charging groups, then set up equivalent Android groups using iQOO 7 phones at 120W for fast charging and 18W for slow charging. After 500 automated cycles over 167 days, with a separate untouched iPhone as a control, the differences were small. The iPhone slow group lost 11.8% capacity; the fast group lost 12.3%. On Android the fast group actually lost slightly less — 8.5% against 8.8%.

Holding a phone between 30% and 80% did help, but modestly: 4% less loss on iPhone, 2.5% on Android across the same period. Storing phones at 1%, 50% and 100% for a week powered off produced no measurable difference at all. Their conclusion for anyone still nursing a charging routine was to stop bothering, and they were candid that the finding took three attempts across several years to produce.

PhoneBuff's two-day test on Samsung's current folding line landed five days ago and makes the point that no database entry can. The Fold 8 Ultra carries 5,000mAh; the standard Fold 8 carries 4,800mAh. The smaller-battery Fold 8 outlasted it: the Ultra died 54 minutes into the final app-cycle stage, the Flip 8 at 1 hour 22 minutes, and the Fold 8 two minutes later. PhoneBuff called the latter pair a tie. The Galaxy S26 Ultra, meanwhile, reached 2 hours 22 minutes in that stage and was never seriously threatened.

So the mid-range phones announced this week with 8,560mAh and 10,000mAh cells are genuinely doing something new. What none of the available numbers tell you yet — not capacity, not watts, and not a declared cycle rating whose recent movement nobody can convincingly explain — is how those cells will be behaving in three years. The first silicon-carbon phones shipped around three years ago in small volumes. The real sample size only arrived recently.