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Recomendations: How to set up an extra battery for my system

fluxwildlyuncut

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I was thinkin of addin an extra battery in the boot of my car to run my system off and was wondering what is the best way to do it and if anyone had any recommendations or advice on the best ways to to it.
 

kopper69

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This is a common practice for 4wd's etc who want to run accessories but dont want to discharge their main battery. Just before I give any advice though, have you considered upgrading your battery? Adding a second is a bit of an investment, few hundred dollars by the time you get the equipment, cable and the second battery. There is also the time running the cable through the car and the potential risks if the power cable was ever to get damaged and short out. You may be better off spending a bit more and getting a better battery?

Anyway if you are still set on the idea of a second battery, you will need to go and purchase a dual battery kit. If you want you can purchase a kit from jarcar and make one up from scratch. The kit basically consits of a switch which can be either manually controlled or automatically controlled. For your application, go for an automatically controlled. This switch will disconnect (or isolate is the word used) the main battery when the car is turned off and leave the second battery (or auxillary battery) to supply power to whatever needs it. In this case the audio gear. You can run the battery fairly low, to a point where it wouldnt normally start the car. But when you go to start the car, the switch (aka solenoid) will switch back to your main battery so that you can start the car without any problems.

The car will charge your main battery back to full and then, because it is automatic, it will charge the auxillary battery.

With a manual system, you need to do the bits that the automatic solenoid would, so you need to remember to switch a big switch each time you need to use the auxillary battery so you dont drain your main battery. Good if you dont use it often, but not good for your example.

Mounting the battery. Batteries cannot be enclosed. They need ventilation to remove the gases that are created when they are used. Just remember that when looking for a spot and make sure that the battery could not ever move once it is in.

If you want to research more look up 'dual battery kit' or something like that for a heap of information. When you make your mind up you can go to a 4wd or camping place and purchase one of these kits. Installation instructions will be included.

You do have the option of simply joining the second battery in parallel, but it is not recommended. This will give you a much bigger combined capacity, but both batteries will discharge to the same level, meaning you may not have enough juice to start the car. It also adds a huge demand on the alternator as it now has to charge twice as much as it normally would.

Good luck, let us know what you decide on.
 

Tasmaniak

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Have you considered the use of a Bat-Cap?
 

fluxwildlyuncut

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Cheers for the great feedback!! i already have a cable run for the battery (the one going to my amp presently), and was thinking of making a little box or compartment for the battery behind my sub (lucky i didn't though).

The only reason i wanted an extra battery is that i was worried about draining the battery listenin to music and then being stuck somewhere. I got caught out installing and adjusting everything and it only took about 15 mins for the battery to run flat.

However, how well does installing a capacitor on the power line work. If that will help out my battery and give me a little extra power, then i might go that way. What sizes dio you recommend?
 

Tasmaniak

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Not a capacitor....but Bat-Cap. It looks like a motorcycle battery but it's capable of supplying around 800A for approx 30secs... Taken from a Bat Cap manf website

What is a BATCAP?

A conventional battery, as we all know has a positive and negative terminal. The chemical reaction within creates a flow of electrons, causing an electronic device (in this case an amplifier) to work. The stiffening capacitor is similar to a battery in that it stores a charge. The fundamental difference is it cannot create electrons. It can only store and supply (discharge) them upon demand. The advantage with a capacitor is that it discharges in one twenty thousandth of a second, unlike a battery that does in one second. The battery therefore cannot discharge fast enough to effectively supply the amplifier and this is the reason for "power sags."

WAKE UP! Don't fall asleep just yet, we're getting to the exciting part!

The XSTATIC BATCAP© is simply a battery that can discharge just a s quickly as a capacitor. Therefore, you have a constant supply of electrons that will discharge at lightning speed. This puts less strain on your stock alternator and battery. It also recharges faster than a conventional battery since the internal resistance is low. How about the install? Well I'm sure you can find a place to put this 2.5lb. baby and his 5lb. big brother. Don't let the size fool you though. These BATCAP's can crank your car, and you can bet we put that to the test!

The cost is another remarkable feature since the 300 model costs the same as a "High End" stiffening capacitor and the 400 model costs a little more. Remember, "good things come in small packages." (I was going to say that "SIZE" doesn't matter but, let's not offend anyone now.) Oh, by the way, the fact that the BATCAP© is capable of discharging in a RUSH over a 5-10 second period SCREAMS three letters, "SPL!"

Home of the Batcap
 

kopper69

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. I dont think a bat-cap is what he needs by what he has mentioned. It sounds like its not much more than a cap. The site doesnt mention anything on capacity, but I would guess that this thing wouldnt provide power to the car for more than a minute once the car is off, giving up most of its juice on a few bass notes. Its advantage is that it can provide alot of power in a short time, I dont think its capacity is any advantage though - and what we want is power for a longer time, which is what a battery offers. Would still be recommending a dual battery setup.
 

commsirac

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The only reason i wanted an extra battery is that i was worried about draining the battery listenin to music and then being stuck somewhere. I got caught out installing and adjusting everything and it only took about 15 mins for the battery to run flat.

Ok, what you perhaps really need is a timer or a battery voltage sensor that will shut down your stereo.

Im not aware of commercially available devices here.

One way which I couldnt atest to working perfectly all the time is to have a relay controlling power to the head unit and to put a resistor in the trigger lead to the relay which will cause the relay to trigger off once the batt falls below 12.4V or so, however, though this would be sensitive to voltage fluctuations caused by peaks in the music.

Perhaps explore the timer route.
 

Tasmaniak

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. I dont think a bat-cap is what he needs by what he has mentioned. It sounds like its not much more than a cap. The site doesnt mention anything on capacity, but I would guess that this thing wouldnt provide power to the car for more than a minute once the car is off, giving up most of its juice on a few bass notes. Its advantage is that it can provide alot of power in a short time, I dont think its capacity is any advantage though - and what we want is power for a longer time, which is what a battery offers. Would still be recommending a dual battery setup.

heh, it helps if I read his first reply properly eh? Although a bat-cap is HUGELY advantageous over a capacitor it is definetly not what we want here.

This gentleman either needs a dual battery isolator set-up or a battery saver device. Which is common in newer vehicles. Anything left running after the car is shut off is automatically shut off after a set period of time or when the battery falls below a set point. There are plenty of devices out there for this which is probably recommend over the second battery route.

Koolatron 12V Battery Saver – Car Battery Saver – Automotive Accessory

A device such as this wired in through ACC on your headunit will work well...or even on the remote line of your amplifier. Just need to be wary that it doesn't shut off on heavy bass beats?
 

Not_An_Abba_Fan

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Run the second battery but use a deep cycle. Have an automatic controller so that you don't have to worry about forgetting to switch it back all the time. As kopper said, it will automatically isolate the cars starting system when switched off so you are only running the accessories off the auxillary battery.

You can enclose a deep cycle to a point, but not fully. There are battery boxes available that are held in by a strap.

The only downside is room and weight.
 
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