Questions and Answers

Dangerous Battery Testing Advice???? Q. I read an ABOUT.COM article at The Charging System See below the text in question on this web page. I am told by many people that what you advise is highly dangerous and quite likely to lead to serious injury. Please see the very recent newsgroups thread at "Put wire inside car battery cell to measure voltage?" Dated Nov 25, 2006.

I feel I should report this to you as it would remain on my conscience if someone got very badly injured and I was aware of the possibility but had not informed you. Would you be so kind as to review the contents of your web page to see if it is unsafe.

Thank you, John S.

The individual cells can also be tested with a voltmeter. Take a coat hanger and make two lead extensions about six inches long and attach them to the meters test leads. Touch the positive lead to the positive terminal and stick the negative lead inside the cell next to it. It should read about 2.1 to 2.3 volts.

Now insert the positive lead in the first cell and the negative lead in the second cell. Proceed down the line until you get to the last cell. Here you will put the positive lead in the last cell and the negative lead on the negative terminal.

All the cells should read the same, or within 0.2 volts. If one reads 4.0 or more, you have a shorted cell and the battery is no good. If you get a very low reading or a zero reading, the cell is open and again the battery is no good.

A. I was the one who wrote that article and described the test procedure you quoted. It is a standard and legitimate test of a batteries cell condition. In my youth when I took my auto electrical courses, it was taught as part of the curriculum. I have even seen it taught in factory training classes.

And if I remember correctly, it used to be on the NIASE certification tests.

Of course you do need to take the normal precautions when you do any kind of battery testing and servicing such as wearing approved eye protection and acid resistant clothing and gloves and working with adequate ventilation. But when done properly, it is a safe test to perform.

After reading the entire thread you point out, I have my doubts about some of the "many peoples" ability to check the air in a tire, much less offer advice on something they know nothing about.

Bottom line is: it is a valid testing procedure and I stand by what I wrote.