Samsung Galaxy Watch 9 suffers from heat wave, ice bath cuts charging time in half

The Samsung Galaxy Watch9 ($409 on Amazon) and the Galaxy Watch Ultra2 are designed to be charged with the official charger at up to 5.5 watts. The Galaxy Watch9 is supposed to be able to fully charge in just over an hour – at least according to the estimate displayed by One UI Watch after a charger is connected. Since the smartwatch’s launch, however, numerous Galaxy Watch9 and Galaxy Watch Ultra2 users have taken to Reddit to complain about significantly longer charging times ranging from 2.5 to 4 hours.

The smartwatch heats up to as high as 44 °C during charging. An experiment by one user, who connected the charging puck to a metal heat sink using thermal paste and submerged it in an ice bath, shows that this high temperature is indeed the problem. With this setup, the charging time was reduced to 1 hour and 6 minutes, roughly half the time for this user. The charger’s power output remained relatively constant at 5.5 watts until the battery was 71 percent charged. Afterward, the power was gradually reduced – typical behavior for a charger designed to preserve the battery.

Another user was able to charge the Galaxy Watch9 from 12 to 100 percent in 01:08 hours by simply placing a fan behind the watch, even relatively simple cooling solutions can thus lead to a drastically shorter charging time. The fact that so many reports of very long charging times are being published right around the launch of the Galaxy Watch9 and the Galaxy Watch Ultra2 is likely due in no small part to the heat wave, which further exacerbates the temperature issue when charging the smartwatch.