Igloo cooler and dead battery issue
Sorry that you had a bad experience with the Igloo (sounds like we have the exact same setup). Maybe part of it was expectation. This type of unit is not meant to be a freezer, but rather a cooler without the use of ice. Comparing it a ice chest with 10#s of ice is exactly what this this type of cooler is capable of delivering. Not sure why the voltage cutoff did not work to prevent running down your truck battery, as it has worked perfectly for us ('02 Ford Explorer SportTrac) over several trips. The Igloo draws about 3 amps, so overnight use should only drain 35-40 amp-hours max (assuming 12 hours) and that should not have killed your battery. (vehicle batteries are typically 80-100 amp-hour). Not knowing the age of your truck battery at the time of the incident, it is impossible to know what happened, but batteries in vehicles are meant for starting (ie short, high current drains, followed by quick recharges). With vehicle batteries even a year old, draining them over a longer period and to a deeper level, can often expose issues that would not have shown up until later in the life of the battery. Older vehicle battery's current capacity degrades over time as sulfer builds up in the plates. This process means that the remaining current capacity of a battery at any given voltage (voltage is what the disconnect unit monitors) degrades. There is a point in a lead acid battery life cycle where there is precious little capacity beyond the needs of starting. So, you allow a device such as a cooler to pull 35-40 AmpHrs out, on top of what the residual vehicle electronics draw (even when the vehicle is off), and you have the situation where there is insufficent current capability to turn over the starter.
BTW, there is a way to greatly extend the life of a lead acid battery (beyond the normal stuff such as water, corrosion, etc). Pushing the battery voltage to 15.5V or so for several hours every couple of months (known as equalization) results in the build up of sulfur in the plates to reverse (ie the sulfur in the plates goes back into the sulfuric acid solution where it belongs). This makes more of the lead surface of the plates available for the chemical reaction. Unfortunately, car alternator systems do not push the voltage much above 14V, so the way to perform this on a tow vehicle battery is using an external charger with the equalization capability.
david & bret
'02 Bambi LS
'99 34' Limited
Air Forums # 2159
Past President Heart of Texas Camping Unit
WBCCI # 7548