Review on 🚗 Jebsens 4.8A 24W Dual USB Car Charger with Volt Meter & LED Display for iPhone 7 / 6s, iPad Pro, Galaxy S7, Note 5 & More by Djkutt Kent

Okay that was a stupid signature Although true. The alternator can either fail due to a broken belt or simply because it is worn out. In this case your car will drain the battery for a while because the battery is no longer being charged. Then you pull up, usually in the middle of nowhere, and call a tow truck. These things allow you to see how much juice is going into the battery and how much is coming out. Very easy if you read the instructions. In my more than 50 years as a driver, my alternators have failed too often. The jerk light flashing for "Check Battery" may or may not (often) work in a timely manner, or not work at all. Many cars used to have a voltmeter to see what was going on. Most people don't do that anymore these days. These gadgets are a cheap way to check things and you get USB plugs. Get one now.