wanted for storage of SWMBO's meds aboard, otherwise no sailing - have tried other coolers but they kill my batteries after 3 days cooling and the cf18 (compressor type)I am reliably informed by forumites that the makers claims of 3.5W daily average is about right, which is about 1/8th of the consumption of my current thermoelectric coolbox so I really need one of these but at a secondhand price. Help!