# How to wire 2nd battery and capacitor?



## aSILENTfire (Sep 27, 2012)

I am trying to add a Kinetic hc1400 and a Planet Audio 3.5 farad capacitor to my setup, and its confusing the hell out of me.

I thought I had to run positive to positive and negative to negative between both batteries (one under the hood and one in the trunk), but now I am hearing that you just wire the positive back to the second battery and ground the negative..

Currently I have a power wire running from my trunk to a fuse mounted on my fusebox, next to the battery, and I was in the process of wiring a second wire for the other terminal (positive or negative, whichever one doesn't need a fuse) when I heard I only need ONE wire connecting the 2 batteries..

So.. I wish I could draw a diagram of what I'm thinking, but it goes like this:
Wire positive to positive between the 2 batteries, with a fuse near the battery under the hood,
Connect positive to positive between second battery and capacitor, with fuse near battery,
Connect positive to positive between capacitor and amplifier,
Ground all negatives.

Will this work?


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## minbari (Mar 3, 2011)

aSILENTfire said:


> I am trying to add a Kinetic hc1400 and a Planet Audio 3.5 farad capacitor to my setup, and its confusing the hell out of me.
> 
> *I thought I had to run positive to positive and negative to negative between both batteries (one under the hood and one in the trunk), but now I am hearing that you just wire the positive back to the second battery and ground the negative..*
> 
> ...


you dont HAVE to run a dedicated ground run for the second battery but it wont hurt anything. you still need to ground it to the body.


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## donnieL72 (Jun 20, 2012)

Another thing that alot of people don't think of when running multiple batteries is that you need a fuse at the rear as well. The big fuse is there to protect the wire, not the amps. One just after the front battery. One just before the rear battery. And if your rear battery is far enough away and the power wire is in contact with metal, one after the second battery. Most people will leave out the fuse just before the rear battery. This will protect the rear battery if a short occurs between the two batteries.


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## aSILENTfire (Sep 27, 2012)

What would be the benefit of adding as isolator or relay?


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## bigscarymonster (Mar 29, 2012)

You shouldn't really need the capacitor in that setup.


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## donnieL72 (Jun 20, 2012)

An isolator or relay would be for when you wanted to play the stereo without the car running for extended periods. It would only deplete the rear battery, letting your front battery stay fully charged.


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## MLCS863 (Jan 26, 2017)

I'm running three amps 2 for my bass and one for my
Highs and I have a capacitor and I'm about to buy a battery should I just run the + from battery to battery then ground my rear battery and run + to capacitor and ground it too or connect it to the battery's ground ? And then run + to my amps and run the ground off my capacitor ? Or how should I do it


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## sinusrhythm75 (Nov 18, 2017)

donnieL72 said:


> Another thing that alot of people don't think of when running multiple batteries is that you need a fuse at the rear as well. The big fuse is there to protect the wire, not the amps. One just after the front battery. One just before the rear battery. And if your rear battery is far enough away and the power wire is in contact with metal, one after the second battery. Most people will leave out the fuse just before the rear battery. This will protect the rear battery if a short occurs between the two batteries.


think about what you just said that is inaccurate information fusing is over rated. if you have one power line going from new york to alabama and theres nothing between new york and alabama until you get to arizona except one road block what in between new york and arizona would require you to make a detour until you get to arizona if the power house is in new york and theres a short too long to short too far away is stupid lol current is current if you short anything enough to blow a 300 to 600 amp fuse it doesnt matter how many you have after that lol your screwed and if you think you have the bomb ass system and over rate your amps to look macho and put this big 800 amp fuse inline its going to do nothing if the current or short is LESS THAN that fuse requirements. multiple fuses is pointless at the FRONT. YES PUT A FUSE IN FRONT AT TOP BATTERY PUT ONE AFTER SECOND BATTERY TO CAP (IF YOUR CAP IS A HYBRID IT HAS BUILT IN CUIRCUT PROTECTION SO YOU DONT NEED A FUSE AFTER THAT SHHHH) DONT TELL PEOPLE THAT WANT THERE BIG NICE FANCY FUSE DISTRIBUTION BLOCK THAT LOOKS ALL PRETTY. FACTgetting the right size fuse is more important that putting 4 of them lol. too big not doing any good too many mmmm ok nothing why would you put a fuse at the front and a fuse at the rear BEFORE THEN ONE AFTER thats stupid as hell. the short will originate from one of two places the ground wire if your dumb enough to listen to people and ground it to the negative battery terminal if not then your good, the positive up front on the main battery from there to the back what would require you to need another fuse genius?? a stripper on a pole? the next area would be from your second battery to cap. you dont need another after the cap why?? bc 90 percent of amps have what ??? FUSES. the ones that dont then yes one from cap to that particular amp. unless like i said you have a hybrid digital cap. then the cap will shut down in event of a short.


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## Fish Chris 2 (Dec 18, 2019)

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## sqshoestring (Jun 19, 2007)

You should put a fuse at any battery because it supplies power and can melt a wire, does not matter where the battery is or how many. If the wire shorts it can get power from any battery the wire connects to.

Steel body of a car makes a good ground wire return, however you have to make sure the connections to it are good and your front battery also has a heavy ground wire to body. Have to make sure they don't corrode/etc and cause a problem later.


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