What is the purpose of the 9 volt battery?
The purpose of the small 9 V battery is to back up the memory and maintain settings in the controller when changing the main battery and in case the 12 V battery looses its charge. However, if the controller determines that a sample must be taken, it will attempt to power the pump. It will not have enough power to drive the pump but this attempt will quickly discharge the 9 V battery. Make sure you maintain the main battery charged at all times to avoid this situation. Consider the optional solar panel recharge your main battery automatically.
