How to Use a Voltmeter to check battery condition
A digital voltmeter can check and test electrical components such as a control relay or an ignition coil to help pinpoint a problem area and determine which components need repair or replacement. A digital voltmeter checks AC/DC voltage, amps, resistance, transistors and diodes and has a large digital display for easy viewing. Most digital voltmeters are battery operated and have detachable color-coded test leads.(Black Red)
Can be used to check for continuity of an electrical circuit. A digital voltmeter utilizes two test leads to probe wiring using a sharply pointed rod which is optimal for piercing a wire (to copper inner surface), or testing a fuse and checking the surface charge of a battery. A digital voltmeter is easy to use, first connect the ground clip to a ground source (metal part of car body scrap paint or corrosion for good contact) to test power related issues, and to the positive battery terminal to test ground related issues.
Some Digital Voltmeter Function Range (depending on model)
DC Voltage 200mV to 1000V
AC Voltage 200V to 750V
DC Current 200ma to 10A
Ohms 200 to 2M
Using a Digital Voltmeter to Test a Battery Surface Voltage
To check a battery surface voltage remove the positive terminal protective cover.(keep metal tools away from open terminals)
Connect the + positive side meter lead (red) to the positive side battery terminal. Connect the negative (black) side meter lead to the negative battery terminal.
With the vehicle not running and the car sitting over night the battery voltage (on a 12 volt system) should be between 12.5 and 12.8 volts. under 12V recharge top up on older battery or replace clean terminals. Car engine running 14 volts plus (allow time to regulate) on alternator constant, older cars with dynamo type charging Voltage will vary under load (lights on).
Replace covers after checking remove tools.