Want to switch between two power sources for car stereo (car battery and solar system)

Thread Starter

DelGrowso

Joined Feb 6, 2024
7
I am building a camper van and have a pretty sweet solar system. I just installed a new stereo system (amp, 6 speakers, subwoofer, and head unit) and everything is working great through the car battery like a normal system. My goal is to be able to switch the power source from the car battery to the solar batteries but I am having trouble finding a switch that can power the amperage being put out.

The amplifier I am using is fused at 80 amps and the highest amperage switch I have been able to find is rated at 50 amps. I have read some things about using a relay but I am a noob and none of it is making sense to me.

Was hoping I could find someone with some experience doing this. Really want to be able to bump tunes while the vehicle is off and parked in a cool place. I installed two speakers in the back doors so I could open them outward and play tunes for a group!

Any help is greatly appreciated!
 

MisterBill2

Joined Jan 23, 2018
18,568
Why change over at all??? If the solar panel is connected to charge the batteries, and the sun is bright, then the system will be using the solar generated power anyway. Also, the battery supply probabkly has a lower supply impedance and will be the better choice for powering the system.
 

Thread Starter

DelGrowso

Joined Feb 6, 2024
7
Why change over at all??? If the solar panel is connected to charge the batteries, and the sun is bright, then the system will be using the solar generated power anyway. Also, the battery supply probabkly has a lower supply impedance and will be the better choice for powering the system.
That was one of the ideas I was thinking about but thought it would be nice to have the option just in case. I can't find what the amp will actually pull and I haven't powered it up and tested it yet. It is a 800 watt amplifier that I will be powering and from what I've read it won't pull much less than that even on a low volume. I did my best to calculate how long it would go on the solar batteries at 800 watts, assuming I didn't have any sun or wasn't charging off the alternator or shore power. And if I didn't have anything else pulling from it and I got around 12 hours. Not sure if I did the calculations right but I have 800 AH of battery at 12V, so 9,600 WH pulling 800 watts. Dividing got me 12 hours. I doubt I will ever use it for 12 hours straight but if I ever did get close to a scenario of driving for 12 hours at night or was using other appliances pretty heavy than I wanted that backup. I also have a pretty hefty AC unit I have to take into account for.

I really appreciate both of your inputs though. I am pretty sure I will need to do the same idea with the head unit with some sort of switch so I can get the remote turn on wire to work and power up the amp when the van isn't on. I was going to check out some RV audio forums and whatnot to try and figure that one out but if you guys have any advice there I'd love to hear it.

Thanks
 

Thread Starter

DelGrowso

Joined Feb 6, 2024
7
Alright, I think I may be overthinking all of this and can probably get by wiring it to the house batteries 100%. If I am driving I will be getting charge from the alternator plus any solar so I shouldn't have to worry about draining the house batteries. And when I am not driving I will have it set up the way I want. Needed these conversations to get the brain flowing!
 

tsnyder

Joined Nov 7, 2019
7
I am building a camper van and have a pretty sweet solar system. I just installed a new stereo system (amp, 6 speakers, subwoofer, and head unit) and everything is working great through the car battery like a normal system. My goal is to be able to switch the power source from the car battery to the solar batteries but I am having trouble finding a switch that can power the amperage being put out.

The amplifier I am using is fused at 80 amps and the highest amperage switch I have been able to find is rated at 50 amps. I have read some things about using a relay but I am a noob and none of it is making sense to me.

Was hoping I could find someone with some experience doing this. Really want to be able to bump tunes while the vehicle is off and parked in a cool place. I installed two speakers in the back doors so I could open them outward and play tunes for a group!

Any help is greatly appreciated!
The simplest thing to do is: Turn off the stereo when you want to switch power sources. They almost any switch will be adequate.
 

Thread Starter

DelGrowso

Joined Feb 6, 2024
7
Appreciate the advice @tsnyder but I am not sure that would have worked. Either way a lot of amperage would be going through the switch when it was on as they both have to be hooked up to it. But I think I will be doing away with the switch all together and wiring directly to the house batteries. I will just need a switch for my accessory wire now to mimic the key being turned on and off.
 

WBahn

Joined Mar 31, 2012
30,072
Why change over at all??? If the solar panel is connected to charge the batteries, and the sun is bright, then the system will be using the solar generated power anyway. Also, the battery supply probabkly has a lower supply impedance and will be the better choice for powering the system.
I'd recommend against this -- it risks draining the battery while you are out in the boonies somewhere. At least, with a solar panel, there is still the possibility to let the battery charge so that you can start the vehicle eventually, but not an option if you need to leave at night or if the sun is not out for several days.

If you have a dual battery system that can be isolated, then I'd recommend running off one of the batteries and having the solar panel set to charge that battery.
 

Thread Starter

DelGrowso

Joined Feb 6, 2024
7
I'd recommend against this -- it risks draining the battery while you are out in the boonies somewhere. At least, with a solar panel, there is still the possibility to let the battery charge so that you can start the vehicle eventually, but not an option if you need to leave at night or if the sun is not out for several days.

If you have a dual battery system that can be isolated, then I'd recommend running off one of the batteries and having the solar panel set to charge that battery.
I think there is some confusion as to how my system is set up. I have the vehicle (chassis) battery and then the house (solar) batteries. The only way they are connected is that the house batteries are hooked up to the alternator so when I am driving any extra juice goes to them.

My initial thought was to have a way to switch between the power sources so I could power the stereo/amp when I was driving off the vehicle battery and off the solar when I wasn't driving. But I think I am going to scrap the idea of switching between both power sources and just hook the stereo/amp up to my house battery only.

When I am driving the alternator will juice up my house batteries so I shouldn't have a problem powering the stereo. And when I am parked it will be hooked up the way I want it already.

I don't have any worries about my vehicle battery being drained, only the house batteries but I have 800AH at 12V, a 500-watt panel on the roof, alternator charging, and shore power hookups. So I think I will be fine there. I was probably just overthinking this when I originally made the post and since getting some answers and talking with some RV audio technicians I believe this new way will be much simpler and have less room for failure.

But I appreciate all the input, didn't expect to get this much traction!
 

whsh93a

Joined Jan 1, 2021
5
I am building a camper van and have a pretty sweet solar system. I just installed a new stereo system (amp, 6 speakers, subwoofer, and head unit) and everything is working great through the car battery like a normal system. My goal is to be able to switch the power source from the car battery to the solar batteries but I am having trouble finding a switch that can power the amperage being put out.

The amplifier I am using is fused at 80 amps and the highest amperage switch I have been able to find is rated at 50 amps. I have read some things about using a relay but I am a noob and none of it is making sense to me.

Was hoping I could find someone with some experience doing this. Really want to be able to bump tunes while the vehicle is off and parked in a cool place. I installed two speakers in the back doors so I could open them outward and play tunes for a group!

Any help is greatly appreciated!
This is a common application for boat an RV owners. Don't reinvent the wheel! (Doesn't anyone here own a boat or RV??)
Forca boat, it's switching between "shore" power or internal power.
For RV users it's isolating the vehicle battery from the other, bigger system.
You, of course, need a charge controller between your solar and batteries, too.
https://www.amazon.com/Dual-Battery...f51d64a0b7af3fa8b77392603e65627e&gad_source=1

https://www.pacergroup.net/switches...ransfer switches are a,connect to at the dock.
 

tsnyder

Joined Nov 7, 2019
7
Appreciate the advice @tsnyder but I am not sure that would have worked. Either way a lot of amperage would be going through the switch when it was on as they both have to be hooked up to it. But I think I will be doing away with the switch all together and wiring directly to the house batteries. I will just need a switch for my accessory wire now to mimic the key being turned on and off.
There are 0 ZERO amps flowing if the system is turned off.
 

crutschow

Joined Mar 14, 2008
34,459
what I've read it won't pull much less than that even on a low volume.
Don't know where you read that, but it's likely not true, otherwise you'd have an 800W room heater.
I don't know of any high-power amp sold that doesn't pull power proportional to the load, plus a small quiescent power that it draws when silent.
Otherwise it would require humungous heat sinks and a fan to dissipate all that heat power.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
18,568
Don't know where you read that, but it's likely not true, otherwise you'd have an 800W room heater.
I don't know of any high-power amp sold that doesn't pull power proportional to the load, plus a small quiescent power that it draws when silent.
Otherwise it would require humungous heat sinks and a fan to dissipate all that heat power.
An 800 watt power amp uses an inverter to provide the higher voltages required to deliver that much power. AND that inverter draws a fair amount of current when the amp is not even delivering any sound. The current is higher at full output but it is never "LOW."
 
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