Batteries During Winter/F51 Batt Temp High Fault

UK – Batteries behaviour doesn’t look normal.

During the winter season in the UK, sunlight availability diminishes significantly, and the limited sunlight generated is primarily allocated to fulfilling the daytime load requirements of the sites. 

Consequently, the batteries may experience only partial charging, leading to potential weeks passing without achieving a full 100% State of Charge (SOC). Attaining 100% SOC is crucial, as it represents the calibration stage for the batteries where voltage is aligned to match the soc value. Failure to reach this threshold can result in inaccurate SOC readings, causing deviations and inconsistencies among battery units. For instance, a battery may display 30% SOC when, in reality, it is at 10%. Although the battery voltages may appear consistent, the SOC calculations may have deviated due to the prolonged absence of calibration.

To mitigate these issues, it is strongly recommended that the batteries undergo a 100% charge at least once every 7-10 days.

For those who already utilize grid charging overnight at a cost-effective tariff during the winter period and have batteries located outdoors or in spaces like garages or lofts, it is noteworthy that certain nights may witness the battery failing to charge from the grid. This occurrence is attributed to the temperature of the battery cells. As the cell temperature within the battery descends to 0°C. the battery's charge rate gradually diminishes to zero, preventing a charge from the grid or photovoltaic sources.

This protective measure is implemented to safeguard the cell chemistry in cold temperatures. The reduction in the battery charge rate initiates at approximately 10°C cell temperature. Even in temperatures of 0°C or below, the battery retains the capability to discharge to the load but is restricted from charging.

To restore the normal charge rate after exposure to such cold temperatures, the cell temperature must rise above 12°C. It is important to note that ambient temperature may slightly differ from the cell temperature, and achieving a normal charge rate may require an ambient temperature of around 15°C.

The F51 Batt Temp High Fault that you may have encountered with the L5.12 IP65 batteries.

Upon careful investigation, it has been determined that this error code is triggered when the batteries experience lower temperatures, primarily in negative temperature conditions. Although the fault is labelled as a TEMP HIGH fault, we can confirm that it is indeed related to colder temperatures.

To resolve this issue, we recommend the following:

Allow the batteries to return to an operational state by ensuring their temperature rises above 5 degrees Celsius. To achieve this you may employ a lizard tank heat mat or a similar device, appropriately sized to the battery dimensions, placed on the front of the battery and connected to a thermostat. This will aid in maintaining a suitable temperature.

In the case of the Sun-Batt-5.32 model, heaters can be fitted if necessary to ensure optimal performance.