Top Tips for Building External Power Supplies
You must seal every possible area of water intrusion with special attention paid to holes put into the box. Speaking of putting holes through the box…
Using silicone caulking does not create a seal. It will eventually crack or peel away after cycles of hot and cold. You may have gotten away with it, you might swear it is good enough. It isn’t. It is the equivalent of duct tape when it comes to building external power supplies.
Use of cable glands or aviation connectors is the best form of sealing cables going into and coming out of the box. If you feel the need to use that silicon or better yet, hot glue, do that on the inside of the cable gland hole. Silicon does great sealing very small holes not 3/8” gaping holes.
If you will use solar you need a proper Charge Controller for the type of battery you will use. You cannot use a standard SLA PWM charge controller on a Lithium battery just as you cannot use an MPPT charge controller on an SLA.
Buy boxes that have bosses that allow you to screw your battery and charge controller down. This reduces of the chances of something bouncing loose when an animal decides to lick or paw at the setup. Plastic pipe hanger strapping works well for this task.
Do not use spade connector type fittings. If you want to use an SLA solder on a JST connector to the terminals. Even the best crimp fittings with proper ratcheting crimpers will never offer a reliable connection.
Heat shrink wrap is about 10% of the job but makes up 90% of the end result. If you find a device made with nice heat shrink wrapping 99% of the time you have found a superior product and a craftsman that takes pride in their work.
Use double insulated wire/cord for external power cords. Buy solder on ends and after you have soldered these ends on, check for continuity from end to end and from positive to negative. Once you confirm the soldering is done correctly, fill the soldered area with hot glue and thread the backing on. This will greatly reduce the chances of barrel plug corrosion and keep the backing in place.