[CarGuys]

All previous information is correct but first start with the battery state of charge.

This can be checked with a volt meter, battery load tester or better yet a modern capacitance tester. A battery that is not capable of holding a charge will not allow the cars charging system to properly work.

If the battery is recharged and then passes its stress test next the vehicles charging system must be tested.

A fully charged battery has 2.1 volts per cell or 12.6 volts total. 12 volts is a dead battery! This is referred to as open circuit voltage.

The charging system must push approximately 14.1 volts however it cannot charge a battery that has failed a battery test. So if you have to look for a charger you also must look a technician to test not guess the trouble.

In a very few cases there may be a parasitic draw on the battery. This is some electrical Gremlin that is causing the battery to drain after the key is removed. Typically you do not want more than 50 milli amps of draw.

For this test you need a trained technician. Previous advisement was correct that you may loose radio functions have security problems loose computer strategies or worse.

To sum up a modern car battery helps supply needed electrical reserve to start and sustain the vehicle at idle. With the electrical demands on today’s vehicles a charging system can only maintain the battery not restore it.

Failure to replace a weak battery can lead to expensive alternator replacement.