1. The solar panel does not charge the battery through the controller during the day.

Controller Detection: The red light of the controller indicates that the battery is charging, the red light flashes that the battery is full, and the controller is charging with a small pulse current.

Solar panels: If the connection of solar panels is not very strong, it will not charge properly, usually in the form of a voltage (voltmeter test), the normal open circuit voltage is above 17.5V; but there is no current. This phenomenon is that the wires of the battery board are not connected properly (virtual welding or unstable joints occur during welding). The method can detect data directly by voltage and ammeter after the black electrical cover behind the battery board is opened. If no current is detected directly from the aluminium pool of the battery plate, it indicates that the battery plate has problems to be replaced.

2. When the controller is connected, the positive and negative poles are reversed, which causes the components of the controller to burn down.