Stereo Dilemma

[Madtown_Joe]

I am trying to use a spare battery that I had laying around to power the radio when the motor is not running and use the regular battery to power the stereo when the boat is running. I have hooked up a switch for each batteries so I could switch between batteries. The only problem is that when I flip the switch to use the back up battery the head unit doesn't work. I am getting power to the back of the plug for the head unit. The head unit works fine when I use the boat battery.

Any Suggestions?

 

[bruceb58]

Re: Stereo Dilemma

Are your grounds on your battery common? You don't switch the ground right?

 

[Madtown_Joe]

Re: Stereo Dilemma

Yes the grounds are common. The only thing that is getting switched is the power from the batteries.

 

[cpubud]

Re: Stereo Dilemma

I think you are missing the ground

 

[cribber]

Re: Stereo Dilemma

You need to tie both negative terminals together and only have the positive terminals attached to the switch. You negative battery terminals are your votlage grounds for both batteries and why they need to be tied together for your setup to work.

 

[Madtown_Joe]

Re: Stereo Dilemma

The negative leads are connected together. I have the two negatives going into one and then from the two switches the power leads are 2 into 1.

 

[TMALEGA]

Re: Stereo Dilemma

Ok not sure on your radio but on every aftermarket car stereo i have ever installed had a red and yellow power. If they are not both hooked up then the stereos would not turn on. Might check that both of them are connected the same and not have say the yellow one on only one battery. That is what it sounds like to me but just my humble opinion take it or leave it i just hope it helps out.

 

[Madtown_Joe]

Re: Stereo Dilemma

I think I figured it out. I noticed that the voltage wasn't that high on the second battery so I hooked up to the charger and it started to work. I figured that if the battery was low the head unit would flicker or just work poorly. I didn't think it would just stop working. Does anyone know how long a battery will last with the radio playing off of it? It is just a cd player and 4 speakers.

 

[Madtown_Joe]

Re: Stereo Dilemma

Thanks for the advice!

 

[Silvertip]

Re: Stereo Dilemma

How long ANYTHING runs off any given battery depends on two things. 1) the amount of current being drawn from the battery, and 2) the capacity (Amp/Hr) rating of the battery. Obviously a higher capacity battery will power a load longer than a lesser one. Not knowing what you have makes it impossible to predict how long the stereo will run.

 

[Madtown_Joe]

Re: Stereo Dilemma

I was just asking for a general idea. I don't need to know the exact time down to the minute.

 

[Silvertip]

Re: Stereo Dilemma

I was just asking for a general idea. I don't need to know the exact time down to the minute.

And even if I had the battery capacity and current draw I could not give you time "down to the minute". So do the math -- 3 amp draw (which is a guess) from a battery with 60 AHr capacity means the stereo would run for 20 hours. Six amp draw means the stereo would run for 10 hours. Condition of the battery (age and its condition) will shorten the numbers. Those numbers take into account the fact that the battery can actually deliver its rated capacity. The stereo will run even after the battery falls out of its specification but you would not likely be able to start the engine from that battery. Electronics have high and low voltage cutoff points so once battery voltage gets to 10.5 - 11 volts the stereo will shut down and you essentially have a dead battery. Best I can do for you with no other information.