Automated Battery Load Tester

Thread Starter


Joined Feb 4, 2012
Hi! I am new to this forum and hoping to get some assistance on a project.
I am an electrical with the ability to build all most any project but weak with it comes to the electrical engineering.
I have several solar installations that I am responsible for and as a part of routine maintenance I have to test the individual batteries capacities. I know there are other far more elegant methods of testing deep cycle lead acid batteries but I haven't the money for any thing like an impedance tester.
So I fall back of the simple Reserve Capacity test. A typical test is like this
390 Minutes @ 25 amps @ 80º F to reach 5.25 volts
Well 390 minutes is a long time to sit around a wait so I am proposing making a tester such as is diagrammed in the attached .jpg
The first component and what I would like to concentrate on now is the load.
I need a constant 25 amp load with a voltage variation of between 5.25 and 6.35 volts.
I am thinking of a circuit similar to the one in the .pdf attachment but it has far to little current carrying ability.
Is it possible to use it together with a larger "pass" transistor(s), to increase its current capability?
What would such a circuit look like?
Or have you all got better ideas