Brandnew Chicago 03418. Trying to charge at 12VDC-10A 2 very dead and very big Duralast 12V Marine batteries in my motorhome. Battery cables disconnected, + and - clips on the anodes. The needle went off the scale to 0%, drawing max Amps. After a few minutes the charger started to smoke. Let it cool off, tried again. 3rd time, just let it go. 5 minutes later, heard a sharp click and charger shut off, green light came on, needle stopped at 7Amps. Let it cool off again, hooked up 2nd battery. Again, needle pegged at the end, there is a humm but no smoke. Charger housing hot to the touch. After 1/2 hour, needle moved a hair, but still at the high end. With the sharp click (and I thought I heard a re-set click 5 minutes later), do you think I burned-up the charger and if so, why ? What is recommended, 2A or 10A charging ? What is the approx time we are looking at for a large dead battery ?