I was wondering now that I will be putting my safe in a hot & nasty environment if it would be best to have just a simple passive, canister-based dehumidifier inside of it (in addition to all the disposable desiccant bags I already threw in there), or to get an electronically rechargeable dehumidifier, and use my safe's 1 tiny little porthole to wire a cable through it, somehow.

Any dehumidifier unit recommendations for the safe?

https://www.midwayusa.com/product/1138359695?pid=453246

^This

If you want to be extra careful you can toss in a rechargeable one in case the power goes out or the goldenrod fails. Haven't had an issue with mine. It does get a bit hot to the touch so I wouldn't put it where any polymer will be touching.

I second or third or whatever the goldenrod. I have one hardwired into my safe along with the motion activated lights.

I have a golden rod in each of my safes and never had a problem with rust forming on my firearms.

Years ago, I used cannister desiccants and then those Eva-dry electronic dehumidifiers.  I didn't like them.  Finally, when I got my new Liberty Lincoln safe, it came with a golden rod dehumidifier and I was hooked.

So are these goldenrod dehumidifiers a generic concept after Goldenrod made the first one last century (quite literally), or are models like these on places like Amazon and eBay made by "MAX Safes" the same as Battenfield's, which is the current incarnation of the Goldenrod (after the former company bought out Goldenrod a few years ago)?

All they are is a low temp resistive heater.
They don't actually eliminate moisture, but by keeping the interior just a few degrees above ambient you're always above the dew point, so no condensation and no rust.
Have had the same one running 24/7 for 10+ years without issue.

So quality then shouldn't be called into question, buy one from Battenfield or MAX Safes, they should be the exact same thing then?

In a truly humid environment, a Golden Rod alone is not going to cut it. I had a safe in an unconditioned garage in central NC, with only a Golden Rod and had big issues when the weather turned warm and humid in the summer. There was mildew all over everything. Thankfully I caught it in time before things rusted to any irreparable degree. I was able to remove the surface rust that occurred with Kroil and some elbow grease without any ill effects. I learned an important lesson.

After that, I decided to use a multimodal approach.

You can attack the problem by increasing the temp inside the safe above the dew point, reducing absolute humidity (dehumidifier) inside the safe, or both. There are those who argue that because the safe is not a closed system that using both methods is counterproductive, as the more humid ambient air will find its way into the safe to achieve equilibrium within the safe. I have not found this to be the case.

I personally prefer to use lightbulbs and a PEET dryer to raise the temp.
https://www.peetdryer.com/products/safekeeping-peet


Additionally, you can use volatile corrosion inhibitor (VCI) chips/packs.

I like these:

Zerust VC2-2 NoRust Vapor Capsule - Pack of 4 https://a.co/d/40l315Y

VCI molecules sit on the surface of metal and prevent the electrochemical oxidization process. The beauty of VCI is that the appropriately sized chip/capsule will protect a certain volume. Choose the right size and replace per manufacturer’s instructions. The VCI molecules treat all surfaces (including cracks and crevices) within the treatment zone. More information can be found here:

https://daubertcromwell.com/vci-education/how-vci-works/

I use dehumidifiers (the rechargeable large EvaDry desiccant type), a 40 W lightbulb, PEET dryer, and VCI capsules (changed every two years).

My safe is stored in a room with HVAC. In the past it has been in an unconditioned garage and in a basement that vents to the outside with standard basement vents.

With my setup, in all those scenarios it stays about 4 degrees warmer than ambient temp and around 47-50% humidity.

I also have a powered dehumidifier in its current location and the ambient humidity tends to be about 60%.

This is a very well-written post, wish there was an 'upvote' or 'like' feature on this platform. Thank you sir!

Happy to help.

I've been using packs of desiccant for 15yrs now without issue. I bake them at 225deg for a few hours a couple of times a year and in safe humidity stays around 40-50% RH.

Most important thing in my opinion though is to get hygrometers to keep an eye on humidity levels, so that you know whatever it is that you're doing is working.

Well said.

My safes are in my basement which isn't as bad as a garage but I also use the multi-use approach. I have a dehumidifier that runs 24/7 set to 45% humidity with a hose that drains the water directly into the floor drain. Each safe has a Golden Rod and the same rechargeable EvDry desiccant type you use. I recharge them once a week but honestly, there's barely any change in them at all after a week.

I've had the same setup for about twenty years and have never had even the slightest amount of rust or any signs of rust ever on any firearm. I feel better knowing they're being properly taken care of and that they'll all be in perfect condition when I die and my son inherits them.