As mentioned above , I want build a cooler box where both TECS rated (12V/6A) are connected in series where it is powered up using Lipo battery (11.1V where fully charged will be around 12.5V).And im using a separate battery (another lipo) to power up arduino , motor driver and fan .So in this project , there are few set points available in the range of (2-15C) and I want the cooler reach the set point within 15 mins where the capacity is about 15Litres. In order to control the temperature , i want to use the PID where it controls the current pass thru the peltiers accoding to the set point but ,my point here is ,how to implement this ? I have read somewhere by using mosfet but im not clear abt it. Can anyone help me on this ? Apart from that should I use heatsinks and fans at the cold side of tec or the attach it to the interior of the box which is made up of aluminium sheet , which will be better ?