Multi-use speaker system?

From what I understand the head unit and speaker system in most vans run off the SLI battery, meaning you can’t utilize the system with the van off without the risk of draining the SLI.

Is there a workaround for this, either drawing from the other batteries or running the same speakers off a separate audio source? I know in AV that some amplifiers can switch between inputs but am not sure if vehicle based amps have similar options.

Been searching the forum and the YouTube to see if I can find anything addressing my question but to no avail. Basically I want to invest in a better speaker system but I’d like to be able to use it parked without having to install a second system or rely on supplemental wireless speakers.

Any ideas or resources I’m missing?

A good source for audio options would be discussing your issues is Crutchfield. Their reps are really good. They have all the schematics for all vehicles. If you decide to go with a different head they include all the adaptor cables so you don’t have go get into cutting wires, just plug and play. It would be a lot easier than going in and trying to change the power from your stock switched system. Especially with new systems interfaced with everything you could open a can of worms. Plus an aftermarket head is going to have loads of input output options, Bluetooth etc.
My system, I removed the stock head, replaced with a Sony Unit, is wired directly to the batt. XM,BT,USB. The head 25x2 powers the cockpit doors 6” speakers. The line outs run to the rear to a Clarion 10 band EQ. The Clarion has an a/b input so the Sony Head runs to Channel A, Channel B input comes from my audio output from my 18” flatscreens variable audio out. This way the TVs Remote controls the audio so you don’t have to get up change anything. The reason I have the EQ is the audio coming from the different sources have different characteristics. I can run the DVD player, regular TV, or mirror my IPad so I can run YouTube videos through the flatscreen. The audio output form the Clarion goes to a Kenwood 45x4 amp that powers 2 6x9s in the back wall and 2 6” in the side walls in the back. The Clairon and Amp are connected to the house batteries and are switched so I can turn the whole system in the back off when everyday driving when all I need is the Sony. All stock speakers were replaced with Pioneer. This system Rocks! When you watch a movie, your there.
If you have any questions give me a shout, will be happy to help.


A double pole, double throw switch connected to the power in on the radio should allow you to switch between battery sources.

An easier solution that might even be more popular is to just wire the radio to the house battery permanently. This works perfectly if you are also using an isolator. You just need to make sure the radio is turned off when not in use.


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Aftermarket shop manual will probably have the electrical schematic and color codes for your wiring. So you know what your getting into for ideas and options.
Parts Express catalog for audio/AV hardware and speakers.
Blue Seas Systems for HD DC wiring, fuses, ACRs and accessories…