Running stereo off auxillary battery
Submitted: Monday, Feb 14, 2011 at 20:25
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Wainy
On the weekend I flattened my starting battery by having the stereo on while polishing/vacuuming/armour-alling. No biggy, a jump start and it's all good.
But....I had assumed wrongly that my dual battery system would prevent this.
It turns out the auxiliary battery is for the 12v socket in the back (fridge) only, which is rarely used. (This was already wired when I bought the vehicle).
My question....can I safely wire my (Alpine) stereo to the auxiliary battery (with in line fuse), switched by a relay on the cars accessory feed? An maybe add UHF, other 12v sockets, etc.
Or is there a better way of protecting the starter battery without a $400 battery management system, in case of head/interior lights left on?
The main battery is a Century High Performance cranker, the auxiliary is a Century Deep Cycle. There is an isolator fitted. I'm not sure of the brand but looks similar to a RedArc. Vehicle is an NP Pajero (2000) petrol.
Also, while on the topic, how do I wire 2 volt meters, 1 for each independent battery?
All suggestions appreciated.
Wainy
Reply By: rolly170 - Monday, Feb 14, 2011 at 21:52
Monday, Feb 14, 2011 at 21:52
Hey Wainy, i would consider a few things before you spend to much money!
First of all most fourby,s have fairly large batteries 650-800 cca (Cold cranking amps) unless you have a heavy stereo set up ie subs etc, i would first have your main battery load tested.
Secondly, battery soloniods dont have to be expensive infact i know of two (Redarc & a cheaper brand supplied by Ashdown's) that both have smart modules on them to supply the correct charge to the right battery. Just keep in mind all these items will connect both batteries when ign is on, so your stereo must work on acc thus keeping 1 battery isolated. Both these units can have a start wire fitted to them to enable starting off the second battery if the other becomes flat, remember if one battery is bad it will try and bring the second battery down to its level and you will end up with two dead batteries.
As for your volt meters they might look great but serve little purpuse as i have seen batteries read 12- 12.5 volts and not start you car you can get small devices that monitor battery condition and audibly warn if they are becoming flat.
if you need more help contact me via my web site as we drive fourbies tooooooo.
mechanicwoolgoolga.info
Cheers Noel.
AnswerID:
445454
Follow Up By: Member - Graham H (QLD) - Monday, Feb 14, 2011 at 22:10
Monday, Feb 14, 2011 at 22:10
Exactly I charged both my batteries for 24 hours each after the car wouldn't start after sitting for a week.
Both had 13.5 volts in them 2 hours after I removed charger.
Car wouldn't start.
Why.
Instead of putting out the 650CCA they were supposed to they both were under 350CCA.
End result 2 new batteries.
Its what they do under load so volts virtually means nothing when just sitting.
FollowupID:
717722
Reply By: 1533rl - Monday, Feb 14, 2011 at 22:54
Monday, Feb 14, 2011 at 22:54
Wainy, I have an 04NP and have just rewired the stereo power to come from the aux battery. I already had a line from the aux to the uhf, so tapped into that, and so now, no keys required in the ignition for stereo.
There were two power cables to the stereo, one was ignition-on for use and the other was constant power for preset functions on radio. I was careful to rewire BOTH cables to the aux so that I do not connect the batteries through the stereo. Maybe not an issue but I am happier about it.
Wiring diagrams available on the net or from the pajero forums. Pretty easy to do, worst part is removing the dash parts. Also have twin 12v sockets where the ashtray was, wired through a seperate switch but still from the aux battery. Once you have the dash out it is amazing what you will think of doing.
Like others though, I am very surprised your stereo flattened a battery in such a short time.
Cheers
Peter
AnswerID:
445466
Reply By: Evakool - Tuesday, Feb 15, 2011 at 14:23
Tuesday, Feb 15, 2011 at 14:23
Hi,
Every after market stereo I have seen / installed have three main wires for power, a ground, a power and an ignition.
So you should be able to keep your ground the same and if the head unit only comes on when at Acc or higher than the ignition has been taped into a line that is working, so leave that, just change where the power wire goes, from the main battery to the Aux battery.
This will run the head unit from the Aux battery, but still only run when you want it to, and if your Aux battery is isolated it will only run down that battery.
Also, you should really find out if your Aux battery is getting run down with your main battery, or the voltmeter has just been setup wrong.
Thanks
AnswerID:
445518
Reply By: tonysmc - Tuesday, Feb 15, 2011 at 14:44
Tuesday, Feb 15, 2011 at 14:44
Hello Wainy,
There is a way around this, I have been using the below setup for years and IMHO it is the only way to go.
The whole idea of a dual battery setup is that you run your accessories and still be able to start your car. I think we all agree on that. The way I do it is you connect EVERYTHING to your 1st battery (as if you only have one battery). Whether you want to use Starter, deep cycle or AGM it doesn’t matter. Then with your 2nd battery connected with whatever system you prefer (redarc, solenoid, etc) you connect ONLY the starter motor main wire, not even the smaller starter solenoid wire.
Your ignition is still going through you 1st battery which is also running everything else in the vehicle. You only need enough power in this battery to operate the starter motor solenoid, not the actual starter motor. If you do happen to flatten this battery completely you only have to clip a small wire or a jumper lead between the positive terminals, the solenoid kicks in and away you go.
I hope this all makes sense,
Cheers Tony.
AnswerID:
445521