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are you talking vehicle electrical? Engine to chassis, chassis to battery negative, and alternator to battery positive? I would not touch any of them coming off the battery/alternator. The alternator is an ECU controlled unit and there is a current/voltage sensing unit on the battery negative terminal that MUST not be altered/bypassed for the alternator to work. If anything, you could add another engine to chassis ground strap. If you're doing this for an audio system, you might be better off running a second battery or just a really good battery in general. If you're doing this to improve performance, it won't change anything.

As for instructional, you can find the Factory Service Manuals and in the engine electrical section will be a wire harness diagram showing the grounding points.
 

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Discussion Starter #3
It’s for an audio system. If I’m running 1500w RMS do you think just an upgraded battery could do that?
 

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I don't know audio systems. I just know the Juke alternator/battery and the charging system is sensitive and does not like non-OEM repairs or modifications.
 

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I'll bite at this...

If you have a true 1500 watt output, and the amplifier has at least 80-90% efficiency, then your power needs are somewhere in the 1666 - 1875 watt range. On top of the vehicle's power needs for the engine and other accessories. Those usually run about 20-40amps, depending on headlights, braking, etc.

Doing electrical math, W = Amps * Voltage.

OEM alternator is 110 amp.

90A * 14.4V = 1584W output from the alternator. Assuming it is really pushing hard.

You need from 1666 to 1875 for the audio + 576 for 40A vehicle needs = 2242W to 2451W output from the alternator to run all of this.

Batteries don't add power, they just extend capacity. A literal capacitor can help in this case to provide power during peak draw, but it will still continue to drain the battery until it is dead, even while running.

You aren't able to upgrade to a different aftermarket alternator to get increased output. I doubt you can take the alternator to a shop and have them add winds to increase power, because it will probably screw with the ECU communication and throw the system off.

So, realistically, you need to work backwards. You have 1500W output from alternator and 600 is needed from the vehicle to run, leaving you with 900W of headroom (rough estimate). That's about all you are going to get out of the vehicle for your system, anything above that will drain it.

As far as the big 3, it's not worth it. You won't be using as much as you think. 900W is 62.5A of juice. Get a 50A fuse at the battery, get a good run of cable to support your distance to your distribution block in the back. Add a 1F cap and be done with it. Without major investment (if even possible) you aren't going to get a competition level daily driver out of the juke without throwing codes or babysitting your battery. Many new vehicles are like this and the old days of just slapping in some extra fat wire and extra fat electricals are long gone.

Good luck!

Previous post for reference:
 

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Also, 1500rms would probably rattle the little car until it died. To figure out RMS to/from watt, it's .707 - so 1500rms/.707=2120watts and at 90% would be 1900watts so I think @Bargeld your numbers are conservative.
However I=P/E (current=watts/voltage); 1900/12=~158amps just for the amplifier. Even running I think is 13.8v? So 1900/13.8=~137amps. Not gonna happen. Sorry dude.
 

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The .707 is just the amp efficiency. I said 80-90% (which is a best case scenario for a class D digital amp). Yes being conservative to show that even best case scenario wasn't really achievable. Real world though... People will wire it up, pound it out, and kill their battery and/or alternator and just chalk it up to the cost of doing business for their 15's. I should also mention that real world, true RMS is about $1 per watt for the amp, with diminishing returns (meaning high power amps cost more per watt). Unfortunately, I can count the amount of times that people actually have the power they claim on one hand. But it's fun to bring science and math into the topic in the hopes that people are comfortable with what they hear and possibly motivated to learn more and trek deeper down the path. (y)

The only real way to know how much juice you have is to blow fuses!
 

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Discussion Starter #8
For reference I was gonna run a Skar RP-1500.1D at 1 ohm. I have another little amp running 75w x4 at 4ohms for the doors. Are you saying I shouldn’t try to go over about 900w rms?
 

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All the fancy math aside, it boils down to one simple concept:

Car electrical system + audio system uses X amount of power
Alternator provides Y amount of power

If X is greater than Y, then the extra power is drained off the battery.

I will say that a $190 amp will not produce a constant 1500 watts, it will be considerably less (this is another audio discussion as well, as there is no regulation in the industry regarding power output claims, but there is a "gentleman's" agreement to use CEA testing guidelines for reporting power output, which this amp does not use).

Beyond that, like all car mods, it's ultimately up to the owner to make their decisions.
 

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Discussion Starter #10
Thank you kindly. I think I will step down to the 1200 model and call it a day. If it dims, I’ll throw a cap in and pray about it lol. Thanks so much for your help.
 

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Also, don't forget you'll need a minimum #2 copper power wire if the amp has it's claimed power.
Back-in-z-day I used a #4 to power a PG XS2300 ([email protected] - birthsheet showed 2x321 so I was happy) ran it in 2ohm mono so 621rms for a couple of 12s, had enough thump, more than enough for me actually so I don't see why you want 1200rms AND have your 75x4 - you want "boom-boom" obviously and heck, you'll be deaf within a year so it's wasted money :ROFLMAO: :ROFLMAO:
 

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Your ears will bleed before your drain the battery using that amp/system. Bargeld is almost always correct with his audio knowledge BUT Get what you want. Show it off once in a while. Get her Thumping. You will not go into negative battery energy so fast it will kill your battery. What matters is the normal listening power usage. You are not competing with this.
 
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