The system voltage is stored in non volatile memory.
In case of a 24V battery, a reset (to 12V) occurs only when the output voltage decreases to less than 2 V and the voltage on the PV input exceeds 7V. This may occur when the battery has been disconnected before PV voltage starts to rise in the early morning. When the (24V) battery is reconnected later during the day, the system voltage is restored to 24V after 10 seconds if the battery voltage exceeds 17.5V.
The controller can be reset by short circuiting the output and applying a voltage exceeding 7V on the input (for example with a small power supply
, or a solar panel) during a few seconds. After a reset, the controller will automatically adjust itself to a 12V system, or a 24V system(when connecting a 24V battery with at least 17.5V).