How do I check my battery to see how much of a charge it has?
You can test the density of the electrolyte with a hydrometer, there are special battery ones for this, but if your battery is old and sulphated then this won’t help . The best way is to check the terminal voltage with the engine off and all accessories off, then check it again with all the headlights etc. on. If the terminal voltage falls below about 11V this is a bad sign. Should be about 12-12.5V for a good battery on load. Note that an icy battery will be sluggish to respond, i.e. voltage on load may fall quickly. Test again when warm.
The only other way is to load test it. This can be done by anybody as long as they have the tool and know what they are doing. Any Autozone, Napa or other part store can do it. And I believe it is no charge or very minimal. What a load test does is check the “life” of the battery. Just because you have 12 volts at the battery does not mean it is good. When you crank the car over the battery uses voltage and a load test makes sure it does not go below specifications.
