What Inspired the WeatherXM Power Expansion System

What Inspired the WeatherXM Power Expansion System

Background

In mid-2024, while exploring new developments in decentralized weather networks, we stumbled across the WeatherXM project.
We were immediately excited by the vision: enabling hyperlocal weather data from independent station owners around the world.

Wanting to get involved — and test the platform firsthand — we bought two WeatherXM D1 | WiFi stations and deployed them outdoors here in the Midwest.

Because we knew the Midwest winters can be brutally cold, we opted to power both stations using Energizer Ultimate Lithium AA batteries, known for their excellent cold-weather performance as recommended on the WeatherXM manual for the WS1001 with the WXM D1 WiFi gateway.

Early Success — and a Surprise Failure

For the first five months, the stations performed flawlessly.
Through rain, early snow, and freezing temperatures, they kept transmitting data reliably.

However, as winter deepened, we noticed something unusual:

One of the stations suddenly stopped reporting.

After troubleshooting the system externally and confirming that the solar panel appeared fine,
we brought the unit indoors and began probing the internal voltage rails.

It turned out the battery reserve had gone flat.
The station had simply run out of energy.

A Look Inside: What's Powering the WeatherXM Station?

Curious, we decided to disassemble the station to better understand its internal energy architecture.

Inside, we found as advertised by WeatherXM:

  • A 5.5V 5F supercapacitor serving as the main internal energy store.
  • No internal lithium battery — just the capacitor and the external AA battery input.

Profiling the Station's Power Consumption

We next power profiled the station to understand its behavior:


Using bench tools, we measured an average draw of approximately:

1.2mA at 3.3V

Given the internal 5.5V 5F supercapacitor,
we calculated how long the station could survive without solar input purely on the capacitor:

Math 1: How Long Could the 5F Supercapacitor Last?

Using the basic energy equation for a capacitor:

Where:

  • (nominal capacity)
  • (fully charged)
  • (assumed cutoff for boost converter)

Calculating:

Convert Joules to watt-hours:

At 1.2mA at 3.3V, the power consumption is:

Then the runtime purely on capacitor energy is:

So the internal supercapacitor can only run the station for about 3-4 hours without any solar input.

Math 2: How Long Could the External AA Batteries Power the Station?

We also calculated how long the external battery pack could keep it alive.

Each Energizer Ultimate Lithium AA battery has a nominal capacity of ~3,000mAh at around 1.5V.

Total energy per battery:

With four batteries in series, total pack energy is still:

But since the station operates at ~3V input, the energy available is roughly the same (~4.5Wh usable).

At a consumption of 0.00396W:

So, purely on fresh AA batteries, the station could theoretically last around 6–7 weeks in the dark.

Why That Wasn't Enough

Unfortunately, real-world conditions make this ideal runtime much shorter:

  • Cold temperatures reduce battery capacity.
  • Super low sun angles in winter reduce solar replenishment.
  • Background system activity or battery self-discharge accelerates drain.

Ultimately, the station wasn't able to sustain itself through the winter darkness.

Designing a Better Solution: The Power Expansion System

Seeing these limitations firsthand inspired us to develop a more resilient solution:

  • LiFePO₄ batteries for much better cold-weather performance.
  • MPPT solar charging to maximize winter energy harvesting.
  • Deep energy reserves (20,000mAh+) to cover weeks of low sun.
  • Optional cold weather heating logic to protect the batteries below freezing.

The WeatherXM Power Expansion System is our response:
A true off-grid solar energy platform designed specifically to match the WeatherXM station’s needs — and to survive the conditions that sidelined our first deployments.

Conclusion

Sometimes the best ideas are born out of small failures.
When one station went offline, we realized there was a gap between rugged field needs and available off-grid power solutions.

The WeatherXM Power Expansion System is our answer:
Built from real-world experience, tested through winter, and ready to help your station stay online — anywhere, anytime.

Back to blog