Cold-climate solar charging for LiFePO₄ batteries!
With the introduction of the 525 series, our data loggers have become even more energy efficient. As a result, versions equipped with the compact integrated 1 Wp solar panel are now suitable for deployment much further north, where the annual solar yield is considerably lower.
In these regions, however, the brightest sunny days often coincide with freezing temperatures. Since charging conventional LiFePO₄ batteries below 0 °C is generally discouraged due to the risk of lithium plating, valuable solar energy may go unused.
Under normal conditions, LiFePO₄ batteries are typically charged at around 0.5C. In contrast, our integrated 1 Wp solar panel can deliver a maximum charge current of only about 0.05C, approximately ten times lower. Such a low charge rate greatly reduces the risk of lithium plating, especially when sub-zero charging occurs only occasionally. In addition, charging is automatically terminated once the battery is full, further limiting any potential degradation.
Based on these considerations and extensive testing, we have lowered the battery charging cut-off temperature to −20 °C, allowing valuable winter solar energy to be harvested while maintaining excellent battery life for typical monitoring applications.
However, for applications that are expected to experience prolonged charging below freezing, we recommend using the LFPLT-26650-3400 (IFR-26650-34D) Low-temperature LiFePO₄ batteries specifically designed for sub-zero charging.