Samsung Galaxy S25 Ultra charging speed Review & Buying Guide: Features, Trade-Offs & Value

② Expert Analysis

Every figure below is labelled by origin. No charging measurement was produced for this review.

The claim, and why the lab beating it is good news with a footnote

Samsung’s claim is deliberately narrow: up to 65% in around 30 minutes (manufacturer claim). It carries the word “around”, it stops at two-thirds, and it says nothing about a full charge. GSMArena’s laboratory test of this exact model, run with Samsung’s own 45W adapter, recorded 41% at 15 minutes, 72% at 30 minutes and a full charge in 59 minutes (third-party lab results) — seven points ahead of Samsung’s claim at the half-hour mark, and a full charge just under an hour. That direction of error is welcome, but the claim’s wording still matters: “up to” and “around” mean the 65% figure is a ceiling under Samsung’s conditions, not a promise for every charger, cable and temperature. The honest expectation is “roughly two-thirds in half an hour, full in about an hour” — competitive for a Samsung flagship of this generation, and slower than the fastest-charging rivals, which is a fair description of where this phone sits rather than a fault in it.

The cable surprise — the in-box cable is enough

The most useful finding in the laboratory’s test is not a percentage but a cable. On its first run GSMArena used Samsung’s 45W adapter with a 5A cable, as the previous generation had demanded. On further testing it found this model no longer needs a 5A cable to reach its maximum charging power: the 3A cable supplied in the box peaked at 39W (13V/3A) with the same 45W charger (third-party lab finding) — higher voltage, lower current, the same charging power. The practical consequence is that the fastest setup does not require a special cable purchase: the cable in the box and any USB-PD/PPS charger capable of the needed output should deliver the fastest charging the phone is capable of. A charger without the PPS profile, or a damaged cable, will not reproduce the laboratory’s curve. And no charger comes in the box at all, so a buyer starting from nothing still needs to buy the adapter — only the cable is already in hand.

The wireless lane — 15W, with a case-shaped condition

Wireless charging is 15W (manufacturer specification), unchanged in wattage from the previous generation and lower than the wireless wattage the successor generation later reached. The headline wattage is only half the story. Samsung does not claim built-in magnets for this model, and GSMArena’s charging section confirms the phone complies with the Qi 2.1 standard and, per the Wireless Power Consortium listing, takes up to 15W, with no Samsung proprietary pad above 15W found: the 15W lane is reached with a magnetic case that aligns the charging coil properly. Without the case, alignment is by hand and the top wireless speed is not assured. That is a real, recurring cost of the wireless setup — the case, not just the pad — and it is also the trap for buyers coming from phones with magnets in the body: the snap-on feel they expect will not be there until the case supplies it. A higher wireless wattage printed in pre-launch leak lists for this model is wrong for the shipping device and must not be quoted here.

Reverse charging and battery protection — small lanes, honestly labelled

Reverse wireless charging at 4.5W (manufacturer specification) is a convenience lane for earbuds and watches, not a way to rescue another phone: 4.5W is slow by any measure. Battery protection, as described in GSMArena’s review of this model, offers three behaviours — Basic, which avoids holding at 100% during long plug-in periods by waiting for the level to drop below 95% before charging again; Maximum, which caps charging at a chosen 80%, 85%, 90% or 95%; and Adaptive, which applies the Maximum ceiling overnight and switches to Basic before waking — plus separate toggles to turn off fast charging for wired and wireless. These are review-described settings, not Samsung specifications lines, but they matter to the charging story because a phone capped at 80% will look “slow to full” to a buyer who set the cap and forgot it. Check the protection setting before blaming the charger.

When charging slows down in real life

Three slowdowns are normal and should not be diagnosed as faults. Charging speed falls as the battery fills, so the last stretch always takes longer than the first-half pace suggests. Heat throttles charging, so a phone charging in sun, under a thick case on a warm pad, or while gaming will slow itself down. And a worn battery charges differently from a new one; Samsung’s published battery story for this model gives no typical-use figure to measure against, only the 31-hour video-playback claim under lab conditions, so a battery that no longer matches its new behaviour needs assessment rather than a new charger. What is not normal is no charge at all, charge only at one angle, or a port that will not hold a cable — those are the symptoms the repair guides below address.

Before calling it slow

Run the checks in order: the charger’s profile (45W USB-PD with PPS for the fastest wired lane), the cable (the supplied 3A cable, in good condition), the wireless setup (a Qi2 magnetic case if 15W wireless is expected), the battery-protection setting (a forgotten 80% cap explains many “won’t fill” complaints), and the battery’s health. If all five check out and the phone still will not charge, the fault is in the phone, not the setup — and the port and battery guides below are the next step.