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Thread: Question on battery caps, second battery and hooking it all up.

  1. #1
    Who am I? HiJackZX1's Avatar
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    Question on battery caps, second battery and hooking it all up.

    Im almost done with hooking everything up. With that being said, I have questions about secondary battery and battery cap. I am trying to go this route to keep from having to buy a high output alternator, which runs $600.00 for my truck. Here is my issue, I do not understand how to install everything.

    Here is how I wanted to hook everything up.

    12V side: Battery > Fuse > Battery > Capacitor > Fuse > 4 Slot Distro Block > Fuse > Amp

    I wanted to know about the ground side though. Is it ok to run the capacitors ground to the ground point on the battery, which then runs to chassis. Most things I am reading is that the cap has to have its own dedicated ground point. Why is this? If it turns out to be true.

    Am I going to have to separate my Car PC units from this or is it ok to have it all together?

    Final question, with a cap, and second battery, do you think this will kill my need for a HO alternator?
    Last edited by HiJackZX1; 01-06-2012 at 10:51 PM.
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  2. #2
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    "Electrically" the grounds are all the same. With that said, there are times when it's best to tie the ground directly to the battery (often with audio ground-loop issues) and other times when it's best to tie it to the chassis. That's a rather ambiguous answer, I know, but in the case of a Cap, I believe either will work. If you haven't already purchased both, you MAY find that one or the other may solve any issue that you may be having that requires them (if you just need more power a second batt. can help, if your lights dim on big bass hits a Cap may help, I'm sure Soundman will have a better answer here but I've seen more and more competition audio guys moving away from caps and toward high capacity, quick discharge batteries designed for car audio).
    As far as not needing a H.O. Alternator with the addition of these two, that may be true.... or it may go the other route and make the need for a bigger alt. even greater. It depends on how you use your system. I have a second batt. setup in my Jeep. When the Acc. circuit is on, they are connected through a solenoid and they disconnect when the Acc. circuit is off. This way, the PC, Amps, Scanner, etc. (connected to the Second Batt. side of the circuit) is normally powered off both batt.'s and the alternator when the Jeep is running but can also be ran off the second batt. alone when the vehicle is off. The only issue with this, which may affect you and is why I mention it, is that if you run your system off the second battery for a while with the truck off, when you turn it on and charge the second batt. off the alternator it creates a big draw on the primary battery and the alternator. Over time this may wear out your alt. and require replacement.... but then again the way I see it, you can run off the factory alt. and see what happens. If it dies, replace it with a bigger one, and if not, that saves you some cash. The risk is that one day, your truck might not run (if the factory alt. dies) and then you'll have to wait on a new unit to arrive.... just gotta weigh the risk.

  3. #3
    Raw Wave
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    Forget the cap. No need in your case (unless you have >2-3kW audio and AGM batteries).


    Your wiring should be:
    Battery > Fuse > battery isolator > fuse > Battery > Fuse ( > Distro Block > Fuse) > Amp.

    See my posts on the "UIBI" (battery isolator) if you have a charge light or other charge indication. (The UIBI is merely a relay controlled by the charge lamp/indicator.)

    You only need to upgrade the alternator if (1) it isn't recharging your batteries sufficiently, or (2), you want full voltage at all loads (eg, 14.4V versus lower (typically below 12.6V) at higher volumes.


    And GND is GND. Though often the amp GND is connected to both the aux battery -ve and the chassis/body GND (whether parallel or low-resistance series).
    As to whether GND is the main battery -ve terminal or the alternator body or engine depends on whn you want tyhne highest voltage - ie, when the alternator is charging or the (main) battery is discharging (if no isolator), though the difference should be trivial after the added GND straps etc (eg, "the big 3").

  4. #4
    Who am I? HiJackZX1's Avatar
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    The way I currently have it is Battery > Fuse > 200 amp Relay > Battery > Fuse > Distro Block > Fuse > Amps.

    The relay works with ignition. How do I determine it isnt charging? Dead battery? Also I just dont want dimming. Before I had very small amps and the 320 Opus and the dimming was annoying. Now I have bigger amps, 2 car pc units, and way more electronics. Im just worried things wont hold up.
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