Your voltmeter is probably different to mine. If you have access to a digital multi meter test your system to check if your dash mounted one is accurate. As a general rule of thumb you should get about 12.8V at rest, dropping to about 10.5V while starting, once running it should charge at 13.8V and even when revving the motor it shouldn't exceed 14.5V.
If don't have access to one go buy one, they're not that expensive. Learn how to use the basic functions on it but try not to get baffled by the advanced functions cause you probably will never need to use them.