Amp wiring with a second battery

[browneye253]

I'm finally moving towards a two battery setup this season. This weekend I wired up my second amp and hooked up my tower speakers. All of this is connected to my main battery. Turned everything on and all was working great.

I drop in a second battery and move the power and ground that go to my amps to this battery. I then turn on the stereo and nothing. My stereo is still connected to the main battery with only the two amps running off the second battery.

I check voltages at the distribution block and get 12v, check it at both amps and it shows 12v. Amps still don't power on. Move the cables back to the main battery and they turn right back on.

My question is what the heck am I missing? My theories are I need to connect the two batteries grounds so that everything is running off the same ground or two, move the stereo and amps to the second battery. My feeling is that for whatever reason the remote wire isn't sending the right signal or power to the amps.

Anyways, obviously my first time w/ a two battery setup and was hoping someone could help me out.

[Okie Boarder]

There's no reason I can think of that it wouldn't work. Although I have my entire audio system on my second battery, it shouldn't matter. The grounds shouldn't matter as far as I know.

Did you check the obvious like making sure your accessory switch or whatever is on to power the stereo? Remote wire is still hooked up? Things like that?

[browneye253]

Yep, all had power. We even tried two different batteries as the second one and still no luck. I was a little baffled as to what it could be. The only thing I was thinking was maybe something weird since the radio and thus the remote wire were on one battery and the amps were on another.

I plan to experiment this week hopefully have something figured out before the holiday weekend.

[jjaszkow]

browneye253, I think that you are on the right path with your remote wire theory.

The remote turn on circuit is incomplete (no connection to ground). To test this, disconnect the head unit amp turn on lead, make a jumper with a small (2 amp or less) inline fuse and connect the turn on to the 12v source for the amp. I suspect you will discover that your amp turns on.

In order to resolve this issue, you can either move your head unit to the same battery as the amp(s) or connect the grounds of the two batteries together. Typically when I've built multi-battery systems for car audio, I've used a common ground.

[browneye253]

jjaszkow, What you described is the correct answer. All of the stereo equipment needs the same common ground. I ran a cable between the two negative terminals on the batteries and the amps fired right up.

Still deciding on whether or not to add a battery switch or just bring a charger and charge up the batteries every night this weekend.

Now to run the speaker cables through the tower so it doesn't look so ghetto. Thanks for the help guys.

[Okie Boarder]

Does them having the grounds together drain them both when you play the audio system? I would guess not since the amps don't have a complete circuit on the engine battery, just the house baqttery. Do I have that right?

[browneye253]

Correct. It's just like grounding a second battery to the chassis of a car. Both batteries are grounded together but not completing a circuit.

[jjaszkow]

Okie Boarder, that is 100% correct. That is also why when browneye253 didn't have them connected, his amp turn on didn't do anything (the circuit was (+load nothing) rather than (+ load -).

[Okie Boarder]

Learn something new every day.