Ifanr test: iPhone 18 Pro, Pro Max hit 50% in 15 minutes with SPR AVS

In Ifanr's measurements, the iPhone 18 Pro charged from 0 to 57 percent in the first 15 minutes, or about 9.7 watt-hours, and reached 84 percent in 30 minutes, maintaining an average power of 40W for 13 minutes. The larger iPhone 18 Pro Max held a 54W peak for the first 10 minutes, charged to 50 percent in 15 minutes, or about 12.1 watt-hours, and reached 80 percent in 30 minutes.

Apple's official specification says the iPhone 18 Pro series can charge to about 50 percent in 15 minutes, five minutes faster than the iPhone 17 Pro's 20 minutes, but the claim requires a 60W charger and Adjustable Voltage Supply, or AVS. Ifanr said the key term is SPR AVS in USB PD 3.2, not the EPR AVS often listed on high-power power banks. Apple launched a 40W dynamic power adapter, rated up to 60W, with SPR AVS support alongside the iPhone 17, but third-party tests found the iPhone 17 still used a fixed 15V profile.

Ifanr tested with CANDYSIGN's IonFlow software and recorded full charging curves. It described the handshake between charger and phone: the charger first sends a standard voltage list without AVS and asks whether the phone recognizes AVS; the phone answers yes; the charger then presents AVS profiles, and the phone requests 18V. Ifanr said this ask-first approach avoids connection failures with older devices that do not understand the new profiles.

Once AVS was established, the phones kept voltage near 18V for almost the entire charge. On the iPhone 18 Pro Max, Ifanr recorded about 18V and 3A, or roughly 54W, for the first 10 minutes. Voltage stayed steady while current stepped down, producing about 36W near 15 minutes and about 26W near 30 minutes. The iPhone 18 Pro briefly hit about 48W, settled near 40W until about 13 minutes, and then declined.

Both phones exited AVS at around 95 percent battery. Voltage switched from 18V to 5V for the final low-current stage. Ifanr recorded this at about 52 minutes on the Pro Max and about 44 minutes on the Pro. It attributed the shift to lithium-ion charging behavior: high current is used early, while a small current tops off the battery near full, making the 18V channel unnecessary. Because SPR AVS has a 9V lower limit, the phones must leave AVS to use a fixed 5V profile.

Thermal performance was also measured. Ifanr said the iPhone 18 Pro's chassis peaked at 38.7°C during the first 30 minutes in SPR AVS mode, a period in which it added more than 80 percent of its charge. The report linked this partly to higher conversion efficiency at 18V and partly to the new iPhones' vapor chamber, which has about three times the area of the previous generation despite an almost unchanged body.

Ifanr offered an explanation for the choice of 18V. EU energy labels list rated battery capacities of 4056mAh for the iPhone 18 Pro and 5391mAh for the Pro Max, and 3C certification information indicates a charge limit voltage of 4.52V, the report said. Four times 4.52V is approximately 18V. Ifanr speculated that the phones likely use a small first-stage step-down followed by a 4:1 charge pump, which would convert 18V input to about 4.5V output while roughly quadrupling current. With a 3A charger output, the battery side could receive about 12A, helping explain how a 5000mAh-class battery reaches half charge in 15 minutes.

The report argued that nearby fixed profiles are less suitable. One quarter of 20V is 5V, well above battery voltage, while one quarter of 15V is only 3.75V, below battery voltage; the latter would require less efficient in-phone buck-boost conversion and generate more heat, with 3A at 15V capped at 45W. At 18V, 45W needs only 2.5A, reducing cable, connector and input losses. Using an example resistance of 0.2Ω, Ifanr calculated losses of 1.8W at 3A and 1.25W at 2.5A, about 31 percent lower, because loss scales with current squared.

Ifanr added that SPR AVS is not optional in the next wave of compliant chargers. Under USB PD 3.2 certification requirements, chargers above 27W must support SPR AVS, meaning most new fast chargers will include it. The report also contrasted SPR AVS with PPS, which can adjust voltage in 20mV steps. Ifanr said PPS's precision can exceed real-world tolerances from cable drop, contact resistance and charger ripple, and that PPS current limits may not reflect available power at a given voltage. SPR AVS uses 100mV steps, reports current limits by voltage range, and has no current-limiting mode, leaving current control to the phone.

Ifanr said Apple has not publicly explained such design choices, but that because the iPhone has not adopted PPS and fixed profiles cannot meet the requirement, SPR AVS became the available path. The test results match Apple's 50 percent in 15 minutes claim, the report said.