This is a battery discharger to measure the capacity of lead acid 12V batteries. The heart of the circuit is the battery protect project. The input from the battery is connected to a 3 digit voltmeter and to the input of the battery protect. The output of the battery protect is going to a ON-OFF-ON switch that selects the load. It is a 68 ohm 5W at one side of the switch and a 6.8 ohm 50W attached to a cooling area at the other.  With the 6.8 ohm 50W exist a 12V fan also. The 6.8 ohm is drawing about 2A and the 68 ohm about 0.2 A. To notify that the battery is discharged a beeper is connected to the unused pin of the relay that is powered when battery is discharged that is placed at the back side of the box. The battery capacity is calculated from the discharge current and the time that passed until discharged. I add a button that permits to discharge a battery that has low voltage and triggers the low voltage alarm.