Assuming the battery is not completely dead, voltage at zero or low loads is not a reliable indicator of battery condition. A load test is what you need. Free at many auto parts stores.
I remember messing around with a scrapped battery when I worked in a service station. After jamming a large screwdriver into the cells and mashing up a lot of the plates, it still read over 12 volts at no load. You only need one working plate in each cell to give you full voltage at zero load, but it certainly won't start the car.
The DIC voltage readout is only useful for determining the charging voltage.