Behavior in winter mode

For customers who have decided to have a battery installed in unheated outbuildings or even in a protected outdoor area, we have summarized information about the behavior of lithium-ion batteries at low temperatures here.

Due to its electrochemical properties, a battery can release less energy on cold days and can only be charged more slowly. This behavior is typical for all lithium-ion cells, regardless of the manufacturer.
The following applies: If you do not charge your home storage system when it is very cold, you protect the cells and ensure a long service life.

Here we provide an insight into how this behavior is taken into account when operating the SOLARWATT Battery vision. Battery management plays a key role in this. It is constantly being optimized and improved, also with regard to charging and discharging behavior.

This information on temperature-dependent charging and discharging behavior can be found in the data sheet:

(Opt.) Operating temperature range Charging: (+20 °C to +45 °C) 0°C to +55 °C

(Opt.) Operating temperature range discharge: (+20 °C to +45 °C) -10 °C to +55 °C

Discharge behavior in winter mode

The discharge behavior develops as follows between the optimum range and the lower discharge limit of -10 °C:

This behavior is replaced from a temperature <3°C and at a battery SoC of approx. 60% . The battery is then no longer discharged. The system switches to winter mode. This is terminated when either the temperature in the battery module rises again to values >= 5 °C or the SoC rises to values >= 65% (5% hysteresis is built in for exiting winter mode). The battery returns to a discharging behavior according to the table above.

Charging behavior in winter mode

The charging behavior develops between the optimum range of > 20 °C and the lower charging limit of 0 °C as follows:

The charging behavior is also adapted to winter mode from a temperature <3°C and here with an SoC of the battery <50% . Forced charging to approx. 60% starts. If possible, this is done using solar power, otherwise using mains power. Winter mode is ended when the temperature in the battery module rises again to values >= 5 °C or the SoC continues to rise to values >60% (e.g. because the sun is shining again).