The information in this article is explicitly related to the Tempest sensor device.
For info on AIR & SKY devices, see Battery Power for AIR & SKY
Solar Power Module & Internal Rechargeable Battery
The Tempest device uses an integrated solar power charge module with four south-facing (north-facing in the southern hemisphere), vertically-oriented solar panels. This geometry provides optimal solar charging even in low sun angles at high latitude locations.
The internal rechargeable battery in Tempest is an LTO (Lithium-titanate) type, 1300mAh battery. This is ideal for use outdoors and in extreme temperatures. LTO batteries are safe on the environment and have a very long lifetime of almost 50,000 cycles - which is many years of recharging.
Temperature Operating Range
The LTO battery will continue normal charging up to about 113°F (45°C) and down to about -40°F (-40°C). The battery will continue providing power outside this temperature range for as long as it has a charge which is usually long enough to return to a range where the battery can resume charging again.
How Much Sun Does My Tempest Need?
Not much! The Tempest only needs about 4 hours of adequate sunlight every two weeks on one or more of the four solar panels to operate. This is a rule-of-thumb and your mileage may vary. In the event of extended periods of low light conditions, power management code in the firmware will help your Tempest operate for as long as possible.
- The Tempest device must be powered ON to allow the battery to charge.
- Tempests are shipped with a full battery and should give you about 2 weeks of operation without any additional solar input, but the device should be placed in direct sunlight as soon as possible.
- After initial setup & configuration with the Hub, the Tempest device can be powered off if it is not ready to be sited outside. After flipping the power switch back ON, the LED should quickly flash green, indicating it has reconnected to the Hub and will resume taking measurements.
- The battery will quickly charge to full capacity in strong sunlight. The battery charge controller will halt charging around 2.6-2.8v (absolute max capacity) and then discharge the battery, decreasing voltage to a safe operating range around 2.55v.
Battery Level Indicator
You can check the battery level for your device in the station's status page: In the app, go to Settings > Stations > (choose a station) > tap Status > scroll down to the Tempest device's battery level.
Battery Card Display
You can display a device's battery voltage card in the app. To enable the battery card on the data display, in the app, go to Settings > Stations > (choose a station) > Advanced > tap 'Show Battery Card' > tap Save on the settings menu.
The battery card should then be displayed on the device observations page.
Power Save Modes
Here are details on how the Tempest may conserve power in order to operate for as long as possible. Most Tempests never go below Mode 0 and more than 90% will never go below Mode 1.
Mode 0: Voltage ≥ 2.455
- All sensors enabled and operating at full performance
- Wind sampling interval every 3 seconds
Mode 1: Voltage ≤ 2.415 from Mode 0 or ≥ 2.41 from Mode 2
- Wind sampling interval set to 6 seconds
Mode 2: Voltage ≤ 2.39 from Mode 1 or ≥ 2.375 from Mode 3
- Wind sampling interval set to one minute
Mode 3: Voltage ≤ 2.355
- Wind sampling interval set to 5 minutes
- All other sensors' sampling interval set to 5 minutes
- Haptic Rain sensor disabled from active listening
What if my Tempest is spending a lot of time in a power save mode?
If you find your Tempest is regularly in Mode 2 or Mode 3, you may want to follow these tips:
First, make sure your Tempest is aligned properly: The blue arrow should face North if you live in the northern hemisphere or South if you live below the Equator. The solar panels should be exposed to as much sunlight as possible throughout the day. See our Siting Guide for more details.
Next, be sure to locate your Tempest in direct sunlight, if possible. Its solar panels don’t need much sunlight, but the device should not be located in the shade.
After a short while (3-4 hours) receiving direct sunlight, your Tempest will return to normal operation, even if it was offline. There should be nothing more you need to do.
If you have tried these tips and your Tempest is still struggling to operate, don’t worry. Contact us and we will help get you going again.