Installing 2-way radio - Power Plan & misc. questions

[tweiss3]

Brand new 2025 XLT Powerboost CrewCab is getting a properly installed 2-way radio and a scanner. Traditionally this is 4AWG from positive terminal at the battery to a breaker then a BlueSea fuse box mounted next to the radio decks, a ground bus with as short of a 4AWG wire as possible to the body, and ignition sense from something ignition switched. I have been reading, including the sticky, the 20 minute video on BMS and charging, as well as looking around. I plan on RF decks & fuse box under the rear seat. I do have an aux. battery, and found the nipple on the firewall to pass power through. All of this has brought up a few questions.

1) I'm confused on the auxiliary battery. With all the thread's of bad aux batteries, I assume that powering the radios off that battery is not the ideal situation, and I should go to the engine bay for power, correct?

2) Ignition sense, I'm assuming BCM fuse 22 would be the best place to grab that, I only have a 2.5A max draw for signal. Did I assume correctly?

3) At the battery (I didn't take time to look at the positive terminal), the video mentioned that the BMS has a connection to the positive terminal as well. Is there any concern to what side of that connection I pull power from?

Anything power wise I am overlooking? This is going to be quite the project to make it look like I was never there, but planning is key.

Sponsored

 

[travisN000]

Probably better to wait for someone more knowledgable about these things, but my understanding is that the aux battery & cables are getting power from the main 12v system anytime the vehicle is running, so as long as you are switching the device off with the main 12v ignition, It probably doesn't matter if it is connected to the leads for the aux battery (it is essentially the same as connecting to the same wires at the main battery).

The aux battery disconnects from the main 12v battery and powers the electronics / computers when the truck is off, with the goal of preserving starter battery power for starting.

I added a voltmeter, 12v outlet, and USB outlets to my aux battery with a manual cut off switch and have used it for charging small electronics and running a 12v fridge for a few hour at a time with the truck off, and never had a problem (I use a portable 100aH LiPO4 for the fridge for longer periods). Many will tell you this is not a good idea, but with 4 years and 80k miles I haven't had any real issues. The occasional warning about low power has been easily remedied, by simply turning on the truck and letting it charge the system. As long as there is enough 12v power for the computers to run, they can activate the high volt hybrid battery and DC-DC charging system and re-charge the 12v system when the truck is turned on.