When it comes to cars, one of the most dreaded warning lights is the battery light. It can be a confusing and overwhelming experience for any driver, particularly when trying to diagnose what could be wrong with their vehicle. The short answer is no; a battery light does not necessarily mean that you have a bad alternator. However, it’s still important to check your alternator if your car’s battery light has gone on because an issue with the alternator can cause it in some cases. An alternator helps keep your car's electrical systems running by supplying power throughout the entire system once the engine starts running - including powering up all necessary components such as headlights, air conditioning etc., so if there's something wrong with this component then obviously everything else won't run properly either. To find out if you do indeed have a bad alternator or not, try testing its output voltage using a voltmeter; if it reads below 13 volts then chances are that there may be an issue which needs further investigation from an auto technician. Additionally, pay attention to other warning signs such as slow cranking when starting up or dimming headlights while driving at night time - these could also point towards issues related to your alternator which need addressing ASAP!