wont start on 2002 Jeep Grand Cherokee

the battery is good and so is the altenator at lest it seems to charge but when you shut i off it needs to be jumped to start only for like 30 sec to makrs no sense

1 answer 1 comment
Turn on the ignition switch to the on but not run position do you see an icon on the instrument panel representing a battery, if you do not see this battery icon the alternator is not seeing power to allow it to charge. Start the engine does the battery icon go out. Put a volt meter across the battery terminals with the engine off, at rest the battery voltage should be 12.6 volts if the battery is fully charged. Now get a friend to start the car while you watch the voltmeter, the voltage reading across the battery should read approximately 14.6 volts if the alternator is charging correctly.
Have the battery charged and tested, If it is more than five years old it is more than likely the problem.
im not getting a battery light when this happens think it's the alternator ??