Dead Battery>>

[Zerocygnal]

The battery in my trunk went dead while listening to my system (Stereo Battery) . I have an 8ga wire leading from the positive terminal of the rear battery to the front battery's(engine battery) positive terminal. It should be charging from the altenator and pulling off the front battery as well. What did I do wrong?
Thanks,
Zero

 

[dTERM]

Ok, 8awg is no bueno. For the kind of amperage you're taking about running you MUST have 0/1awg. Understand, that dead battery is trying to draw 650+ amps through a cable that was designed to carry at most 200 amps for a maximum distance of 2 feet. At 16 feet a really high quality 8awg cable is good for around 60 amps peak. Assuming you have about 16 feet of cable, you're lucky it didn't catch on fire. That 8awg cable is fine for a 350 watt amp or lower, but jeeze. I'm running a single, 1000w amp on my 4awg cable and that is the bare minimum. It draws less than 60 amps. Make sure you are grounding that battery to a good, solid spot of the frame and you definately need to run a breaker on each end of the power side. If that cable shorts to ground you're gonna watch your car roast like a christmas turkey. You really should get a battery isolator so you'r car only starts off one battery. They're not really expensive and it'll extend the life of both batteries.

 

[Zerocygnal]

Thanks!
I did eventually figure out that I had to ground that stereo battery to the frame. The altenator was basically ignoring the stereo battery because it was not the path of least resistance. When I grounded it to the frame the battery consistently held a 12.7V charge. The battery isolator is a good idea. I didn't see any problem with the car using both batteries to start the engine, however I take into consideration the awg of the wire and it does make sense. Being that the 8awg wire is only supplying a recharge to the rear battery it shouldn't be a problem with this system. Under long periods of operation the wire remains cool. The power wire leading to the amp from the rear battery feels comfortably warm but thats it. Sounds great too! I'll check into the isolator, thanks!

Zero

 

[dTERM]

The continued draw is nothing. The 8AWG will draw exactly what the stereo draws. What you have to consider is that if you have the car off, and you drain that rear battery. When you start it back up, BANG the rear battery tries to draw it's max AMP rating for a second...probably of 1300 or more CCA (Cold Cranking Amps) then it tapers off to it's CA (Continuous Amp) rating, probably around 650. Once it has a full charge, It will only draw what it uses. That Legacy amp you have listed is a real bad power hog. I won't mince words here, It is a cheap amp, and the cheap Volf speakers connected to it make for a real sloppy power drain. You're probably bouncing between 10 and 70 amps draw from them. I would hate to have you roast your car trying to power a $500 stereo. Really, I'd suggest you pull the battery out and put in a few 1 Farad Caps (1 Farad per 1000w) . They'll deliver power faster than a battery can. The first time you connect the caps, put a 1Meg resistor in place of any fuses you have in line. Good 1 Farad caps will blow out most fuses when the initally charge up. Leave the resistor in the fuse holder for about a minute, then pull it out with pliers. It will get REALLY hot. Anyway, good luck with your stereo...and remember, 12V won't hurt you, so stick your finger in the cig lighter and get over your fear of electricity...Car voltage is nothing.

 

[Zerocygnal]

I'm done dumping money into the stereo. Hell it sounds great and I can't rationalize spending 2g or more on a stereo. I don't turn in up that loud and I don't hear anything that would make me question the quality. I don't see the point in a capacitor because it is only beneficial for maybe 30 seconds to a minute. i might be looking at this the wrong way but the matter of the fact is I can't overshoot my budget on this one subsystem of an entire vehicle that could use improvement. I can cut some corners on a stereo as long as I know that it's within safe limits, with everything else I can only accept the best.

Thanks for the input

 

[ShadyGST]

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