Heatwave

Two heatwaves in June are unusual and unpleasant.

Lithium batteries require careful management of the temperature range for charging, with both minimum and maximum values for safety and battery life.

This module is located outside and exposed to the morning sun. It has a sun shield that is larger than the enclosure, and the unit is mounted on a plastic post to minimize heat conduction. The solar panel is mounted via an aluminum bracket to the top of the enclosure and may be an important source of heat conduction.

Prior to the heatwave, there was more than sufficient solar charging to maintain a 100% battery charge each day, shown in orange.

In the graph below, as the interior temperature, in black, rises above 95 degrees, charging is automatically disabled. For three Both mornings, the temperature is above 100 degrees by 10AM, leaving only a short charging window for the day.

Orange trace is the battery charge (%); turquoise step-trace shows the ambient light level, an un-calibrated sensor.

The heatwave was immediately followed by multiple rainy days with insufficient solar light to charge the battery.