A voltmeter is not an acceptable and accurate method for checking the validity of a battery. It is sometimes tricky and elusive to identify a bad battery. Firstly, drain the charge of the battery to a possible extent. Except in a condition of severe discharge, a bad battery will appear good. The most satisfactory form of draining the batteries is by means of discharging machine. But these machines are very much expensive. Ride the car around or set the back wheels up on jack stands and drive it till it is almost dead, if u doesn’t wish to purchase the discharge machine. This is the only way to distinguish a bad battery. Subsequently, in the discharged state, place amperage drawing load on the batteries.  Using a battery load tester is the easiest way. A good battery holds steady voltage after dropping a fraction of volt. While using the tester, if the voltage of the battery continues to drop off, it may be a bad battery. If necessary, replace the battery. A failing or bad battery will destroy the car.

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