Best way to protect battery powered PCB outdoors: IP65 box, conformal coating, or both?

Hi
My project will see a battery powered circuit live outside. The bare PCB has been professionally manufactured, and I did all assembly work etc.
It will live in a field attached to a post and this area can get quite humid especially in summer if it has been raining earlier. I was going to fit it inside an IP65 electrical box and thought on giving the entire PCB a good spray of "plastikote" or similar.


Does anyone have any better ideas or advice?
Regards

Special 'tropicalised varnish' sprays are available for protecting PCBs and electronics being used in harsh conditions. I wonder if condensation will occur as well, perhaps some silica gel sachets might help avoid that.

Something like this (UK) ebay

Do a search for "diy conformal coat". You should get several ideas for coating the board.The IP65 electrical box should do a good job of protecting the board. perhaps too good...I'd worry about heat build-up in the box outside in the sun and possibly condensation. A drip hole in the bottom would allow any condensation to drip out

Make sure your box is white, or a light colour.  Maybe put a "hat" or roof over it to protect it from direct sunlight (and rain).  And you could also (if you leave it completely sealed) put in some of those desiccant sachets that you often find with new equipment (if you used recovered ones, heat them in a gentle oven before sealing them in your box).

Hi
Thanks to all for the good suggestions. The boxes I'm currently looking at are grey IP65 ones. I'm not concerned about heat build up from the electronics as the circuit will be asleep for 99% of the time, but if the boxes were in direct sunlight (ha ha, what's that here in UK?) then there is the possibility of temperature issues although I think it may possibly be more so for the box than the electronics. Perhaps the lid may warp slightly.I'm not so keen on the drip hole idea though. Nearby an electrician installed some stuff using similar IP rated boxes with the cables fed from below. He made a drip hole but when I looked inside you could see corrosion on the terminals inside. I can't say for certain but I suspect humidity and the holes played a large part as no way did the box fill with water.
Thanks again.
Regards

Does this device require any cables to come in or go out?If the box is well sealed, including the cable entry (if any) then you don't need a drip hole. If the cables are NOT well sealed and enter from the bottom then the cable holes will become drip holes.A light color box with electronics that is asleep will be warmer than the outside temperature but not by a lot.

Following your reply....- put the box on the northern side of the post (where the sun don't shine in the UK - cover the sun-facing sides of the box with aluminium foil to reflect the heat- use silicon sealer on any cable entries - the glands you get these days with rubber washers and compression rings are pretty good, but a bit of silicon sealer makes sure.  Same goes for any LEDs / displays / solar panels.

HiThanks again for all the helpful replies.Good idea about locating it on the Northern side. I agree that the washers on stuffing glands etc are OK but I have found you cannot rely on them to much to keep water out. They seem to have a way of loosening no matter how much you tighten them and if you tighten too much then you damage the washer (maybe I'm getting rubbish stuffing glands <s>). On previous projects I've been known to put a ring of araldite around the base of the gland to secure it to the box if subject to any nearby vibration, and of course a generous application of silicone sealant where the cable meets the gland.However that won't be my main concern in this particular project, I was more interested to find out if there was anything particular I should be doing with the PCB in such a mildly hostile environment. The links above have been very helpful.RegardsPS. I wish I'd known about "Tropical Varnish" when I live in Borneo. Maybe then my 4x4 electrics would have worked...<s>

IP65 enclosure is a minimum, but in the UK should be fine. I recommend spraying the PCB both sides - and any exposed terminal contacts inside the enclosure - with an electrical conformal coating. Do not use anything else; if it's not an electrical conformal coat, it will have chemicals that will corrode your PCB.
https://ie.farnell.com/multicomp/mc002230/conformal-coating-aerosol-400ml/dp/2854864

FYI, I use bluetooth headphones and LED head torch while hill running, twice a week. These devices last only 6 months on average. When I open them up - headphones and head torches - they are filled with corroded contacts. These things are designed for IP65, but still suffer for moisture ingress. So spray your boards and panel mounted connector terminals with conformal coat, and you should be good!

Hi Mike
Many thanks for the advice. At present the units are out for field trial of a few weeks to see what tweaks need to be made and I'm not unduly worried about them. I will certainly take on board all the advice given when going "live".
Best regards

Hi MikeYou mentioning the issues you have with Headlight and Heaphones got me thinking. I have a telescopic sight that has an inbuilt laser in addition to the crosshairs. A year or two back the laser gave up and it wasn't worth the expense to send it off for repair especially as the scope worked perfectly well otherwise.Scopes are sealed units and purged with nitrogen during assembly and I discovered that it was the turret switch that was the issue, not the laser. If I used the turret switch which contained the battery it didn't work but, if I added the pressure switch adapter that extended control to a convenient point, say fore end of stock then it worked fine. The turret controls whilst not sealed per se, do have O-rings and generally speaking do a good job of keeping moisture and dirt out of the battery compartment. I will revisit that switch with a very generous supply of WD40 :)Most of my scopes have an illuminated reticule powered by a battery in a turret switch and have been in use for years in all weather with no detriment, so I'm thinking that I just had bad luck with the laser one (well out of warranty when it started to give problems) but it does sound like a corrosion issue.
Regards