: 1024x788 px
: July 2, 2018
The test procedure is quite simple. Set the meter to read DC volts, and set the correct range if needed. Some meters will select the correct range automatically. Nearly all meters will come with instructions on how to set them to read DC volts. Next, connect the meter across the vehicle battery, positive (+) to positive (+) and negative (-) to negative (-). With the engine running at a moderate idle - say 1200 to 1500 RPM, the meter should read approximately 13.8 to 14.8 volts and be steady. If the reading is substantially outside these figures and all other items mentioned have been tested and verified good, then the alternator is likely defective.
An auto battery is built up of six cells, each containing stacked positive and negative lead plates. These are divided and separated by insulators and immersed in an electrolyte, a liquid blend of sulfuric acid and water. However, some batteries, use a gel instead of the electrolyte. This is considered to be safer and because you do not have to refill it with electrolyte, it has been labelled "maintenance-free". Each cell generates or more correctly put, stores 2.1 volts for a total of 12.6 volts.