Battery Equality Monitor Circuit Schematic

Description

 Almost all 24V power systems in trucks, 4WDs, RVs, boats, etc, employ two series-connected 12V lead-acid batteries. The charging system can only maintain the sum of the individual battery voltages. If one battery is failing, this circuit will light a LED. Hence impending battery problems can be forecast. The circuit works by detecting a voltage difference between the two series connected 12V batteries. Idle current is low enough to allow the unit to be permanently left across the batteries.

Circuit Diagram:

Parts:

• R1 = 2.K
• R2 = 4.7K
• R3 = 39K
• R4 = 39K
• R5 = 1.5K
• R6 = 1.5K
• Q1 = BC547
• Q2 = BC547
• Q3 = BC557
• D1 = 3mm Red LED
• D2 = 3mm GreenLED
• B1 = DC 12 Volt
• B2 = DC 12 Volt

Source -  http://www.extremecircuits.net/2009/12/battery-equality-monitor-circuit.html