How do I test a car battery using a DMM??

Question

Do I test for voltage?? If so, how many volts am I looking for?

Answer 1

A car battery develops a "surface charge" while it is being charged by your alternator, so you have to wait an hour or so after you turn the engine off to properly measure the battery voltage. A fully charged battery should read 12.6 volts. If the battery reads 12.0 volts, it is undercharged. With the engine running, the charging voltage typically reads about 14 Volts depending on the charge condition and temperature of the battery as well as computer controls on some of the newer cars. You can also measure the "parasitic current draw" from the battery after the car has been parked for an hour or so by using the 10 Amp current range on the meter and connecting it between one disconnected battery cable and the corresponding battery terminal. With all the courtesy lights out in the car, the reading should be less than 1/4 Ampere (250 milliamperes). If not, something on one of the fused circuits is drawing too much current when the car's parked and will drain the battery faster than normal.
Another voltage test you can easily perform yourself to make sure your battery is good, is to measure the battery voltage while someone cranks the engine over for you. On a car that cranks but won't start, you should read at least 9 Volts across the battery, because the computer, ignition, fuel pump etc needs a minimum amount of voltage and power to operate correctly.

Answer 2

you want to set the DMM to volts DC (20)
yes, you are testing for volts

If the car is off, you should be looking for voltage to be between 12 - 12.8 volts

if the car is on, then you're looking for your voltage to be between 12.4 to 13.8 volts

Answer 3

car battery should be somewhere around +12VDC....just put the leads on the battery terminals