I use this silicone conformal coating on the boat controllers: http://cgi.ebay.co.uk/ELECTROLUBE-DCA-SILICONE-RESIN-CONFORMAL-COATING-200ML_W0QQitemZ230357947941QQcmdZViewItem?rvr_id=&rvr_id=&cguid=9a13470111d0a0e202874dc7ffd55255
This eBay supplier is as cheap as any I've found. The stuff is easy enough to use, you spray on a couple of coats (leave a couple of hours between coats) and then gently cure it in an oven (after a few hours of air drying time). It completely seals the board up and will penetrate up the ends of the wires a bit as well, sealing them up. The downside of this is that the coating will penetrate under the FETs if they are not tightly screwed down to the heatsink and well sealed with heatsink compound, which could result in a poorer thermal path. Provided the FETs are fitted properly this isn't a problem. The heatsink bar needs to be cleaned up afterwards, or well masked off, otherwise the coating will restrict heat transfer.
The advantage of this type of coating is that the board is repairable. It's possible (but very smelly) to solder through the coating if you need to do any repairs. Obviously the board would need re-coating after repair, but this is better than just having to write the board off if a fault develops.
The epoxy coating illustrated in that video presents a potential problem for some types of controller. Many controllers use a big power resistor to drop the input voltage to the regulator. These can run pretty hot, so coating them in thick epoxy might not be a good idea. There are controllers on the market that are potted in resin, but some have proven to be highly unreliable. Tongxin sold/sell a tiny potted controller, but they fail because of local heating internally. Two that I've seen have had burnt areas around the current shunt, showing that the potting was acting as a good thermal insulating layer, to the detriment of reliability.
Jeremy
