Overpowering a peltier element
15.4V x 6A is over 90W, not 60. So 60W is not the "rated power" but the heat pumping capacity. 

This is in line with other Peltier coolers I've seen - they take about 1.5W of electrical power to pump 1W of heat, whereas a compressor-based refrigerator would pump 3-4W of heat for the same 1.5W input power.

So you can use it at 12V, 5.5A (66W in) and it'll probably pump about 40W. 

Add these together (106W) and add a safety margin : plan your heatsink/cooling to remove something like 120W from the hot side.