A bad battery can cause a car to lose power while driving if the alternator cannot keep up with the battery's charging needs. In older cars, a working alternator provides enough charge to power vehicle accessories. However, newer cars require more electrical power, which makes it difficult for alternators to deliver the required amount without assistance from batteries.
Performing a basic battery check:
Check the battery for swelling and signs of damage and wear that indicate it needs replacement. The battery cables should be in good condition because bad cables do not deliver full current flow. Use a voltmeter or multimeter to check the battery charge. It should read approximately 12.6 volts with the engine off and about 14 to 15 volts with the engine running. Low or high readings may indicate a problem with the alternator, voltage regulator or wiring.