Q: I have a 08 ford focus, its super cold and it tries to turn over but ultimately won't, the battery is giving me 12.3 volts.

When the weather gets cold, I replace a lot of batteries. If your battery is marginal, it will work just fine until the temperature drops, then it won’t have enough reserve to do the trick.Testing it with a voltmeter won’t tell the whole story. You need to test it under a load. If you can put your voltmeter where you can see it, you might find that when you engage the starter, the voltage drops precipitously. To have it checked out, contact YourMechanic. They can send a technician to your home or office to check out your starting problem and replace your battery right there on the spot if necessary