Ok so now that the fridge and the charger are all in the same space i need some ventilation so i came up with something like this.
As i am not sure i can rely on natural ventilation and want to keep the hole in the box doors to a minimum, i am thinking of running a little 12V power fan exhaust with a filtered intake.
The intake and exhaust would be through one of these,
http://www.ebay.com.au/itm/PLASTIC-BOAT-VENT-4-3-4-boat-vents-blowervents-/400187900036?pt=Boat_Parts_Accessories_Gear&hash=item5d2d0ec084#ht_2522wt_1139
The intake would be fitted with a filter which will be about 25mm deep to stop as much dust as I can
The exhaust would have a small mesh filter behind it and one of these,
http://www.oewcomputer.com/catnew/product_info.php?products_id=14143
at 30 l/s and 50 Pa should do the job.
My box is .47m3 in volume and given the air flow i will do about 216 air changes per hours, so one should say it will be OK.
The fan would be run either when the fridge or the charger are on, so easy enough.
What do you think? or a bit of an over kill? i guess if so it would match the rest of the trailer.
How have others ventilated their boxes.
I did think of a solar vent but i will be running a roof basket on top of the box so that's out.