The short answer
24 hours on a single charge, with a 2.5-hour average charging time.
The long answer
To better understand Flow’s battery capacity and consumption, it’s worth digging into a few details.
Flow’s battery is used to power a wide range of electronic components neatly tucked inside the device's stainless steel casing:
- A laser that counts fine particles
- Two membranes for VOC and NO2 detection that are heated up to 250°C
- A fan spinning at close to 15,000 RPM to control Flow’s air intake
Flow was designed for real-time air quality mapping - what we believe is the key to making the subject of air quality accessible and compelling to all. To get there efficiently, Flow functions in always-on mode, making one measurement per minute - if you’re cycling urban streets for example, that’s going to be the right interval for the app to extrapolate and accurately map what you’ve been breathing along the way. Also, as a user you won’t have to worry about whether Flow is on or off - it’s just with you and doing its job.
Flow is always-on in part to be able to make one measurement per minute but also for optimal use of the VOC and NO2 sensor: if the membrane remains inactive too long, it will get “polluted” by external elements. Hence, namely, the 15mn warmup and countdown that triggers when you pair your device with the Flow app for the first time.
Practically speaking, if your Flow was off and you turned it on just as you walked out your front door, you’d have a 15 minute gap in VOC/NO2 readings. Not practical. Always on means the sensor is always at the right temperature and always measuring.
Despite all of these constraints, we’ve achieved a full 24H charge duration out of Flow’s 620mAh battery, about as much if not a bit more than your average smartphone.
Some consumer-grade air quality monitors advertise much longer battery charge duration, maybe up to a full week. They achieve this by:
- Making far fewer measurements
- Not measuring NO2
- Giving less accurate particulate matter readings by sampling less air per measurement
We think it’s a possible choice, but it’s not one we’d be comfortable with :)
Flow comes with a dock that can live at home, on a shelf or on a desk, and have your device elegantly fit into your environment when you are not out and about. It works with what are called “pogo pins” which mean you don’t even have to plug it in for it to charge.
In all situations where you don’t have your dock handy, Flow can be charged using any USB-C cable plugged to a power outlet, computer, or other electronic device via which you would charge a phone, for instance.