Electronics Question for Always on USB

Hey Everyone,

Super quick question. I think I am missing some basic electronics knowledge to easily answer this.

I have an aux relay bank in my 2019. I’d like to run a switch for a secondary 12v run to my center console usb bank.

This way the usb ports are on (stock power) when the truck is on. AND I would have an “always on” switch to power this same usb port when the truck is off(or on and I’ve forgotten).

Question is! if I splice my new 12v power into the stock 12v by the outlet, and both supply power… am I doubling power to the outlet? My assumption is yes… in that case do I need to fuse after they join?

Any help would be appreciated!

 

Is there an always-on mod for the 3rd gens? I know in 2nd gens it was as simple as removing the relay from the interior fuse box, poping it open with a small screw driver, and wedging the contacts shut with a small piece of plastic. The always closed contacts provide power all the time regardless of key.

 

There is, but it requires bridging a relay built into some board in the dash. I was hoping to add something somewhat easy to remove if necessary.

 

That's an interesting approach. There is an always on mod for the 3GT that only requires a bit of soldering. But, if you don't want to go that route...

Putting parallel fuses could potentially pose a problem if both power sources are on if/when a short occurs. Each fuse would carry ½ the current, meaning by the time one fuse blows (quickly followed by the other), you've essentially passed twice the current that the wire is rated to handle. Basically, if each fuse is 10A, and they're in parallel, 20A could go through the circuit before both fuses blow. Note, this is all assuming the short occurs after both fuses, both sources of power are on, and fuses blow at the rated current (usually they go above their rating).

If you still don't want to go the route of doing the always on mod, I would opt for two fuses in series, with your spliced source in between both fuses.