If an AirVisual Node/Pro is kept disconnected from power for an extended period of time, the battery may not charge normally when AC power is applied again. This problem occurs due to a synchronization mismatch between the battery cell and firmware.
In this case, you may notice that your AirVisual Node/Pro immediately powers off when the charging cable is removed, and the battery icon continuously reads '0%,' even when plugged in.
To return your Node's battery to peak-performance, turn your Node/Pro off for 2 solid minutes, and then leave powered off while the device charges for 30+ minutes. This will allow the battery to reach an important 3.6V threshold, after which the device will begin to behave normally again.