Your AIR and SKY devices will report their battery levels with each observation. Users can enable a battery “card” on their dashboard to monitor. App > Settings > Stations > select station > Advanced > ‘Show Battery Card’.
If you use the recommended Energizer Ultimate Lithium batteries (and insert in the correct orientation!), the starting voltage will be in 3.4-3.5v range. Here’s a battery power curve for an AIR in use for over 9.5 months: https://smartweather.weatherflow.com/share/1934/graph/3474/battery/5 . And a battery power curve for a SKY in use for ~4months. (As of mid-July 2018) https://smartweather.weatherflow.com/share/1934/graph/7267/battery/5 .
AIR voltage will remain sufficient until ~2.4v, then the lightning sensor will not have enough juice to function. However, the other sensors will continue to report until ~1.9v.
SKY voltage will remain sufficient and all sensor will function until ~2.0v. (Note: at ~2.2v the lithium batteries are approximately 90% drained.) Users who wish to get more battery life from the SKY should enable the ‘power save’ mode which samples wind every 15sec instead of every 3sec…with an expected life of 2+ years.
We strongly recommend Energizer Ultimate Lithium batteries as they perform much better in fluctuating temps. Alkaline batteries will work, but will not last nearly as long. Rechargeable lithium-ion batteries are not recommended. (We do not have any affiliation with Energizer or receive any reciprocal compensation to recommend. We tested lots of batteries, and those are the best we’ve found.)