Monitoring Device Known as Batwatch

The project utilizes an Atmel ATtiny13V in order to create the Batwatch that will be used to monitor a solar panel battery charger.

During operation, the charge current and battery voltage are periodically measured by this device which is indicated by two LEDs ( green and red) blinking. To prevent a discharge of the battery when a car is not used for some time, it will be built into the plug of a VW solar charger panel. The measured voltage drop across a 10Ohm series resistor determines the charge current. The battery voltage pertains to the voltage before and after the resistor which is measured using two A/D inputs.

The low-power voltage regulator LP2950CZ is used instead of a plain 78L05 to keep the power consumption low. The average total power consumption is about 1mA since the duty-cycle of the low-power LEDs is rather low. The internal BOD circuit has a voltage set to 4.3V and is enabled.

All activities including sampling the two analog inputs, calculating the charge current and battery voltage, and showing the voltage on the red LED and charge current on the green LED is done by the software.

Rest of the project