Second battery quick question

DEpointfive0

Hey guys,

If I want to run a second battery to the trunk, do I NEED to run the -negative as well? Or will the chassis carry enough power to it? Can I ground it twice in the rear?

Thanks in advance!

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DEpointfive0

I have googled it and most websites say you should. Bit they are running 5000 watt sound systems. I'm not, but I DO have a 0 gauge wire running from the front to the rear anyways.

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Mt Tam I am

I think you can but let us wait for anothers opinion.
It works for jump starting a car.

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DEpointfive0

Well, chassis in the front works fine, but I'm wondering if there is any issue with the rear through the welds and stuff and/or if there is enough juice to keep it charged

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SouthArk370Z

The chassis will make a much better ground than just about any cable you could reasonably work with and make fit. Think in terms of cross-sectional area - the chassis has many more circular mils than a battery cable. All that assuming the chassis is made of something that conducts electricity decently - steel and Aluminum work well.

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DEpointfive0

^Would you say running 2 ground cables is overkill then?

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DEpointfive0

And will I be over stressing anything?

I'll have a 250A fuse between the 2 batteries (the internet suggests one at each end of the same wire within 1 ft of each battery, not being an electrician, I don't understand the logic behind that), but will there be any risk to anything because the CCAs will be much higher?

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SouthArk370Z

If you are talking about running two cables from the front to the back, then it's not overkill just unnecessary. If you are talking about using two short cables to go from the rear battery negative to the chassis then it's probably a little overkill but not a bad idea. For high-current applications, you can't have too big of a wire ... but you may have problems making it physically fit in the space you have available, which is why it is so nice that the chassis is such a good conductor.

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SouthArk370Z

What are you doing that you need two batteries?

For the high-current wiring between batteries, it's a good idea to put fuses on both ends in case you have a short in the middle of the big cable between batteries - with one fuse, one of the batteries would not be protected.

Theoretically, each battery will supply half of the current. Of course, in the real world, it usually doesn't work out that way but, with the proper size wiring, shouldn't be too far off.

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DEpointfive0

Ummmmm... For right now let's say I sit in my car for long periods of time and watch movies. It will be just one battery eventually. I have to get my alternator situation sorted (20% UD Stillen crank pulley, and I just ordered a 10% OD alternator pulley from NST to help keep the volts a bit more constant at stops)



I assume that the battery that has the fuse gets the protection? Should I take the fuse out when I do eventually go with 1 battery?

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SouthArk370Z

Might be easier to hook up a battery charger whilst watching movies.

I'm not sure what you mean. If you mean remove the fuse (or fusible link) between the two batteries when using just one battery then it would be a good idea to remove the fuse but not really necessary if your wiring is done properly (and you insulate the end that came off the back battery). If you use only one fuse, I would put it close to the front battery; this will help protect the front battery, and the car in general, in case of a short in the inter-battery cable. If you have a short, you may kill the back battery but the car itself should be safe.

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DEpointfive0

LOL, can't do that when I'm not at home

You answered my question, no worries.
You've been a big help

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