Solar Power & Rechargeable Battery Follow

The information in this article is related to the Tempest sensor device. For info on the legacy Smart Weather Station AIR & SKY devices, please 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.

Operation

• 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.

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.

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

Tempest devices on firmware version 175 and newer have a new dynamic wind sampling power save feature. This replaces the power save modes described further below. 

It will activate when the battery voltage gets below ~2.65V and will be in one of three wind sampling rates: 

• 3s wind sampling, speed (max gust over last 1 min) > 10 mph
• 6s wind sampling, 5 mph < speed <= 10 mph
• 15s wind sampling, 0 mph <= speed <= 5 mph

For Tempest devices not on firmware versions 175 and newer, 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 arrow on the side of the device 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 there is not enough sunlight to maintain adequate power, you may benefit from using the Power Booster Accessory.

If you have tried these tips and your Tempest is struggling with power issues, please contact us so we can help determine if there is a problem.