Wiring head unit and amplifier to van battery and house battery

[Williamssherman55]

Hello,

I just purchased a 2003 dodge sprinter and I am looking to see what it would look like to build a system where I can run speakers in the back of the van and the front while driving normally and while parked running off the house batteries in the back. I saw a wiring diagram a while ago on this forum that seems to look pretty good, but I was wondering how the accessory wire would be run so that it could turn on and off with the key, but then be able to turn on when switched to the house batteries. Has anyone had any experience with this? I am also just considering running a separate head unit and speakers in the back to run off the house batteries as that seems like it might be easier?

Thanks!

 

[BrennWagon]

There are a number of ways to accomplish this, the most straightforward way is to run main power to the radio system from the aux battery and use the OEM signal wire to turn it on while driving, then add a switch to bypass the signal wire from the aux battery. This is essentially what I did and it works flawlessly and I never have to worry about draining the main battery. You’ll want to mount an aux fuse/relay box for the aux circuits. I attached mine to the outside of the back of the passenger seat base and in the almost year that it’s been in place I’ve had zero problems but I have great accessibility if a fuse or rely goes bad.

 

[Williamssherman55]

There are a number of ways to accomplish this, the most straightforward way is to run main power to the radio system from the aux battery and use the OEM signal wire to turn it on while driving, then add a switch to bypass the signal wire from the aux battery. This is essentially what I did and it works flawlessly and I never have to worry about draining the main battery. You’ll want to mount an aux fuse/relay box for the aux circuits. I attached mine to the outside of the back of the passenger seat base and in the almost year that it’s been in place I’ve had zero problems but I have great accessibility if a fuse or rely goes bad.

Thanks for the reply! That seems like a good solution. Do you have a wiring diagram or would you mind quickly drawing one out so I can better understand the setup? Also If I understand correctly, with this setup, the audio system does not rely on the vehicle's battery at all for its power? My only concern might be that I don't want to drain the house battery from just driving and listening to music, however, maybe this could be mitaged by adding the dc to dc charger while you drive. And did you run an amplifier with your setup or just the head unit?

Thanks!

 

[borabora]

I think what you want to do isn't very difficult as described by BrennWagon above. But I think what you want sound-wise might be different while driving versus while sitting inside. I find that to overcome engine and road noise I want boosted bass and attenuated highs when driving. I also want sound to appear to come from the front with a little from the back and the balance shifted to the right. When not driving I want a more neutral sound and possibly coming from a different direction. In other words, consider adding another system instead. If you find yourself mostly streaming from your phone then consider a low cost BT enabled 12/24V amp and some automotive speakers. But if you want the additional benefit of being able to take the sound outside consider one or two BT speakers. You can always mount them to be removable and with charging cables at those locations.

 

[Williamssherman55]

I think what you want to do isn't very difficult as described by BrennWagon above. But I think what you want sound-wise might be different while driving versus while sitting inside. I find that to overcome engine and road noise I want boosted bass and attenuated highs when driving. I also want sound to appear to come from the front with a little from the back and the balance shifted to the right. When not driving I want a more neutral sound and possibly coming from a different direction. In other words, consider adding another system instead. If you find yourself mostly streaming from your phone then consider a low cost BT enabled 12/24V amp and some automotive speakers. But if you want the additional benefit of being able to take the sound outside consider one or two BT speakers. You can always mount them to be removable and with charging cables at those locations.

Thank you Borabora for the reply! That is a good point and I will consider that as well. Certainly using the portable BT speakers would be the simplest/most portable solution. Perhaps if I go with the first route of running the regular sound system while parked off the house batteries, I was thinking about adding a 4channel amp to that system to be able to run another 4 speakers in the back so that it would hopefully sound good whether you were in the front or the rear.

 

[gltrimble]

 

[BrennWagon]

Thanks for the reply! That seems like a good solution. Do you have a wiring diagram or would you mind quickly drawing one out so I can better understand the setup? Also If I understand correctly, with this setup, the audio system does not rely on the vehicle's battery at all for its power? My only concern might be that I don't want to drain the house battery from just driving and listening to music, however, maybe this could be mitaged by adding the dc to dc charger while you drive. And did you run an amplifier with your setup or just the head unit?

Thanks!

@gltrimble nailed it on the wiring diagram. My aux battery system is setup with a very simple battery to battery charging relay.

 

[Williamssherman55]

@gltrimble nailed it on the wiring diagram. My aux battery system is setup with a very simple battery to battery charging relay.

@gltrimble , Thanks for drawing the diagram out! I will do some research on parts to buy now and keep you all updated! Thanks again for all the help!

 

[gltrimble]

@gltrimble , Thanks for drawing the diagram out! I will do some research on parts to buy now and keep you all updated! Thanks again for all the help!

Simple automotive relay is all that is required. On my Pioneer stereo the yellow wire is 12 volt power and the red wire is the 12 volt ignition signal. Colors may not be the same on all radios. Relay link below. I bought a rocker switch labeled “Stereo” but have not yet changed out the “Zombie” switch which currently powers the stereo.

https://www.amazon.com/dp/B01KVZ2MU4/ref=cm_sw_em_r_mt_dp_K90A1QHQ36XT26JY3GR6?_encoding=UTF8&psc=1

 

[Williamssherman55]

Simple automotive relay is all that is required. On my Pioneer stereo the yellow wire is 12 volt power and the red wire is the 12 volt ignition signal. Colors may not be the same on all radios. Relay link below. I bought a rocker switch labeled “Stereo” but have not yet changed out the “Zombie” switch which currently powers the stereo.

https://www.amazon.com/dp/B01KVZ2MU4/ref=cm_sw_em_r_mt_dp_K90A1QHQ36XT26JY3GR6?_encoding=UTF8&psc=1

View attachment 171762
View attachment 171763

Thanks for the link! I like the "zombie lights" switch! I suppose that if I were to add an amp to this system, I could just wire it to the house battery and have the radio turn it on and off and wouldn't need a separate switch making that part of the install also pretty straightforward. Also, just to clarify, when you are running the wire from the house battery to the yellow wire, and then switch to the yellow 12v wire, did you just tap both of those wires into the one yellow 12v wire?

 

[gltrimble]

Thanks for the link! I like the "zombie lights" switch! I suppose that if I were to add an amp to this system, I could just wire it to the house battery and have the radio turn it on and off and wouldn't need a separate switch making that part of the install also pretty straightforward. Also, just to clarify, when you are running the wire from the house battery to the yellow wire, and then switch to the yellow 12v wire, did you just tap both of those wires into the one yellow 12v wire?

Yes, the ignition lead on the radio rarely pulls any significant load. Just acts as a signal to turn on. The radio is always energized.

 

[Colorado_Al]

I just use a switch and it always runs off the house battery. Easy enough to click the switch when I want tunes and never a possibility of draining the starting battery.

 

[kper]

I just use a switch and it always runs off the house battery. Easy enough to click the switch when I want tunes and never a possibility of draining the starting battery.

This is what I did as well. Switched power also supplies the amp 'turn on' signal. With the audio control amp (and I'm sure others), I can toggle the input to be the speaker level input from the mbux head unit or BT direct from my phone (driving vs stationary, respectively).

And dang it gltrimble -- I thought my zombie lights idea was original. Wife made fun of the front light bar only being useful in a zombie apocalypse and then I found the zombie logo. Apparently it is not original content!

 

[mdalysd]

Thanks so much for the schematic...excited to install this switch so I can power our head unit from our house battery. I'm somewhat of a newbie so please forgive me if this is a dumb question, but when I installed my amp I used a wiring kit from Crutchfield that came with 4 awg wire from the car battery to the amp. This schematic calls for 8 awg from the car battery to the relay. Can I attach the 4 awg to the relay? Or can I step down from 4 to 8? Or do I replace the 4 with 8? Thanks in advance!

 

[Inertiaman]

There's a simpler way to do this, with a three position SPDT on/off/on switch and no relay.

In my system, I have the primary power supply to the head unit and amplifier both tied directly to the house battery. I have the amplifier remote turn-on tied to the head unit, as one would in any stereo installation.

Then, for the yellow "ignition/turn-on" wire input to head unit, I have that tied thru a Blue Sea 7482 switch. Terminal one is tied to the12V ignition signal of the van, terminal two is connected to the yellow red "turn-on" wire of the head unit, and terminal three is tied to 12V from the house battery. I used one of Hein's 3D printed switch sockets to mount the 7482 into one of the unused OEM switch locations on the dash, just left of the ignition (on NCV3).

With this arrangement, the three switch positions are (1) stereo goes on and off w/ the engine running, as with any normal car audio install, (2) stereo is off regardless of engine/ignition status, and (3) the stereo is on, regardless of engine/ignition status. In both 1 and 3 "on" cases, the actual 12V *power* supply to both amp and head unit is coming from the house battery, even when driving.

There is one trivial issue with the arrangement: switching between the two "modes" will briefly disrupt the power to the head unit, so it will restart. In practice, this has never been an issue. My default position for general driving is position one. Once I arrive in a camp, or some other environment where I want engine off and music on, I switch it to position three. I could care less if music is off for 10 seconds when switching between them.

As for the front/driving speakers versus the rear/camping speakers, I use the head unit fader. I fade front to rear to "switch" speakers when I am in "camping" mode. My front speakers are in the doors and on dash/A pillars and sound great for driving. My rear speakers are actually two different sets of Speakon female connector terminals: one set in the D pillars at the rear doors, and one set in the little "wall" adjacent to the slider step near B pillar.

In the rear I have speakers semi-permanently mounted on brackets on the D pillars that can point into the van, or to outside. Alternatively, I can quickly disconnect those via the Speakon connecters, and grab a pair of cast aluminum old Boston Acoustics speakers that I use outside in campsites, and plug those into the slider door Speakon sockets. In all these cases, the subwoofer continues to function (and can be relocated if desired, since it is also wired through Speakon sockets).

 

[mdalysd]

@Inertiaman...thank you so much for the response. Your solution does sound much easier and likely one that I'd prefer to try. It sounds logical in theory, but the newbie that I am, I really need a schematic that I can follow. Possible for you to sketch this out? I'll ship you some beer for your troubles.

 

[TrackSprinter]

This schematic calls for 8 awg from the car battery to the relay. Can I attach the 4 awg to the relay? Or can I step down from 4 to 8? Or do I replace the 4 with 8? Thanks in advance!

I may have not been following but… the wiring of the relay requires a sizing relevant to the current it will carry. If youre wiring a switch to power your head unit, you will only need a small gauge.

Wiring power to the amplifiers will require a larger gauge dependent on continuous power (current) requirement and length of run. Try an online wire size calculator if you are unsure.

I am utilizing a switch to divert the amplifiers from the starter battery to the house bank when desired. The switch has 4 positions: 1, 1+2, 2, and 0. Position “1+2” is used to cross over when the amplifiers are already engaged so I dont need to turn the system off to make the switch.

 

[Motormad]

I'll throw another option into the pot - I fitted my head unit with a timer relay and a momentary action switch. This will run the head unit for a preset time (40 min in my case) to avoid leaving on and discharging the battery.

 

[Inertiaman]

@Inertiaman...thank you so much for the response. Your solution does sound much easier and likely one that I'd prefer to try. It sounds logical in theory, but the newbie that I am, I really need a schematic that I can follow. Possible for you to sketch this out? I'll ship you some beer for your troubles.

The image below uses Pioneer head unit color conventions on the wire, but I think they are pretty universal.

As shown, the head unit is powered by the house battery. If you periodically disconnect or turn off the house battery, then the head unit may lose some of its settings. This is dependent on a specific head unit's design, and whether it uses "background" power even when powered off to maintain radio station settings, tone/EQ settings, etc. If this is a concern, you can use the diagram below with one single change: instead of connecting the yellow head unit lead to the +12V house, connect it to an always-on (or direct) connection to the starter battery. Then it will have background power even when house batteries are disconnected; the downside to this is that you will modestly load the starter battery when playing the stereo in a camping situation (with engine off and stereo on, most power consumption will be via the amplifier loading the house battery, but a modest amount of power (10W??) will be drawn from the starter battery via the head unit). Pick your poison.

EDIT: I noticed a minor discrepancy in my drawing versus the long description in earlier post: in the drawing, "camping mode" is switch position 1 and "driving mode" is position 3. My earlier post described them the opposite way. Functionally its the same, it just relates to which "side" of the switch you'd label for which use case.

 

[autostaretx]

Unspoken (that i can find) is how the house batteries are *charged*.

If they're being charged from the Sprinter's alternator, then why switch the radio?
"Just" power the radio from the house batteries.
When the engine is running, the radio's drain would be being supplied by the alternator.

If you're NOT using the engine to charge the house, then i could see rigging up a switch-over.

--dick