Adding capacitors prevents car peltier cooler from making low battery light flicker, but why?
First of all, TMI of the useless sort, not enoughof the useful sort.

That converter is made to operate lights and DC motors.  It probably has little to no filtering of the output, and may use only a half wave rectifier.  It seems to be pretty old.

What that means is, is that it doesn't put out a nice, clean 12VDC, but rather a pulsating voltage that approximates DC.  

The low points in the pulses are low enough to trigger the low voltage warning on your cooler.

Adding the (big) capacitors smooths the pulses and holds the average voltage high enough to stay above the low voltage alarm.

The peaks on the pulses may well be over 16VDC.  You have no way to measure them, and I can't measure it from here.

So, no guarantees that it won't kill your (presumably) expensive capacitors.

Cheaper and more certain would be to use a modern switching power supply rated for 12VDC and 5A.  Check the tags on the cooler, or look it up online to be sure about the voltage and current.

Or, just use a cooler made for 110VAC when you've got an outlet to connect to.



The recommended converter puts out 6A at 12V.  The model number is in the cooler hand book.  Buying one of those is probably cheaper than playing games with expensive capacitors, and safer besides.  Have you considered what could happen if you short those big capacitors?