Quote Originally Posted by jick.cejoco View Post
Just the battery voltage alone is not a reliable measure of battery capacity.
Compare the battery to a low level water tank, even with good pressure ( from the pump), it cannot SUSTAIN the electrical load. The voltage is the electrical pressure, the ability to sustain (current) is the amount of water in the tank.

What I have been doing is loading the battery while checking the voltage. A simple way to do this is to disable fuel delivery and crank the engine a few seconds while observing the battery voltage. If the voltage drops below 11 volts while cranking, change the battery and repeat the test. If the voltage still falls below 11 volts, replace the battery.
Will this kind of test do good for newer cars? From what I understand, you disable the fuel pump by removing the fuse. Is that right? For cars equipped with PCM and with almost all controls relying to computer, will it not give you code error once you disabled your fuel pump?

From what I've read, you can do your own battery voltmeter by connecting two series resistors and parallel it to one resistor. That series parallel resistors should serve as your probe as you connect it to your multimeter. I haven't tried it so I can't remember the values of resistors.