Hi all,
I was just messing about with some old batteries, setting up my DC Load for a battery capacity test. I have two old 9V batteries, both read about 7.5V with no load. If I connect either one to my DC Load and try to pull 500mA, the voltage drops to about 3V, but supplies the 500mA. All as expected so far. However, if I connect the two batteries in series (total no load voltage now around 14.8V) and try to pull 500mA the voltage drops to 0.027V and can only manage around 280mA. I wasn't expecting this, but I'm no battery expert.
I would have expected somewhere around 6V and the 500mA still being supplied, but obviously I was wrong. Is this due to the two ESRs being added together? The maths don't add up for me. Can anyone explain exactly what's happening here?
Thanks,
McBryce.