I Built a 12V Battery System for My Rivian (Rego + VHF Radio)
It has been a little quiet around here, but that is only because I have been in the garage tinkering. One of the projects I wanted to figure out was how to power my Search and Rescue radio in the Rivian without touching the factory 12V system. In a normal truck you would see a dual battery setup that ties into an alternator. Since we do not have an alternator in the Rivian, I had to get creative.
The goal was simple. I needed reliable power for my VHF radio and later on for lights during missions. I wanted something that could stand completely on its own and not rely on the Rivian at all.
I ended up going with the Renogy Rego Super Slim solid-state lithium battery. It is a 12.8V, 104Ah pack with 1,331Wh of capacity. It is slim enough to fit under the rear seat without rattling around and solid enough that I do not need to worry about overheating. For comms, I paired it with my AnyTone VHF radio which is my main lifeline to the team during searches.
I had a spot under the seat that I was barely using, and the Rego slid right in there like it was made for it. Once I had it in place the real work began. I ran 10-gauge wire with 5/16 inch ring terminals, added the proper fuses, and gave the radio its own dedicated line. I have never been much of an electrical guy. I can tear down engines and swap suspensions but stripping wire and crimping terminals is brand new territory for me. With some help from friends online and the Rivian community, I worked through it step by step.
The first time I powered it up I honestly expected something to go wrong, but to my surprise the radio came alive right away. No voltage drop, no drama, just power. That was the moment I knew the project was going to work.
Now a battery is only good if you can recharge it. Since solar is not hooked up yet, I am using a Victron Blue Smart IP22 AC charger. I can plug it into the wall at home or use the Rivian’s bed outlet while in the field. The Victron app makes it easy to keep track of what is going on and in just a couple hours it can take the Rego from low to full.
For now the radio is mounted in a temporary spot under the seat with the antenna run out through a makeshift mount. It is not permanent but it gets the job done. I left the Rego fully charged for a week and it only dropped to 99.5 percent, which I am pretty sure was just the Bluetooth keeping connection with the app.
As for runtime, I would have to transmit on high power for 26 hours straight before draining the battery. If I am talking that much during a mission, then we are probably dealing with a bigger problem than a dead radio.
That is Phase One. A standalone 12V system that powers my radio without touching the Rivian’s stock battery. It is safe, reliable, and completely independent.
Phase Two is adding solar. I have a 210W flexible panel ready to go. Once I install a charge controller and tie it in, the Rego will be able to recharge itself out in the field. At that point this setup will be truly off-grid and ready for whatever Search and Rescue missions throw my way.
This whole project has been a learning curve. The crimps were rough at first, I questioned myself more than once, and I probably annoyed my friends with too many questions. But that is the fun of it. I walked away with a working system and a new skill that will only keep improving. For me, that feels like a win.
