The charger should be putting out 13.5-14 volts when charging the batteries. It sounds like you might be measuring battery voltage and the charger is not working or connected correctly. Disconnect one of your battery terminals and measure the voltage on your battery terminals. If you have 13+ volts on the terminals when the battery is not in the equation, then you know your charger is working. Be careful doing this so you don't short out one of the battery terminals when doing the test.