The inductive button on the left side of the Charge 4 is used for navigation, and we sometimes found it finicky to press.

The outdoor visibility of the screen is reasonable, but when there's lots of sun, and your hands are sweaty, interacting with the screen can be a bit challenging. A lithium-polymer battery powers the tracker, and Fitbit claims that it can last up to seven days, or five hours of continuous GPS tracking. One nice feature is that it is water-resistant up to 50 meters, and you can wear it in the shower, the pool, or when doing some light swimming at the seaside.įitbit Charge 4 has a monochrome OLED 1-inch display that's big enough to show notifications and activity stats, while also allowing you to navigate it with your finger.

It saves daily totals for the past 30 days.

The built-in storage saves 7 days of detailed motion and heart rate data, minute by minute. You also find a 3-axis accelerometer, a vibration motor, an altimeter, and an NFC chip. Fitbit has packed in a SpO2 sensor too, that can track oxygen saturation using red and infrared light. There is also an optical heart rate monitor that measures the heart rate data at 1-second intervals during exercise tracking and at 5-second intervals the rest of the time. The big novelty is that Fitbit Charge 4 has built-in GPS for measuring both pace and distance. Inside the tiny tracker, there are lots of components. The tracker module of the Fitbit Charge 4

Bit charge 4