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no for real thanks alot it helped i was really confused about the whole second battery thing my other question is that i just replaced the alternator with a remanufactured oem one (short on funds) otherwise i would have gotten a bigger one or have had mine rewound. but my question is that if i put a second battery in the trunk (most likely a yellow top) will that be too much for my alternator to try and keep charged? (i have a large Red top in the front) also with a second battery would it help to run an additional 4-1/0 ga wire to the + terminal on the battery in the trunk? i was bored last night so i did the "Big Three Upgrade" i used 1 1/0 ga wire for all of the grounds and i put a 4ga wire from the battery to the alternator because that was all of the wire i had left i tried to fit two 4ga wires on the alternator but couldnt so i settled with one better than nothing i guess. i guess im just nervous to plug my system back in i dont wanna fry another alternator and battery and get stuck at sheets again for a half hour :p but i am going to remove the cap and just run my + wire straight to my amp for now. thanks for the help guys! :D
 

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With only that much power, you really don't need another battery. That Red top should be good enough, and the OEM alternator will be fine for now. I'd for sure loose that cap, it's not going to do anything for you other than looks.

I'd get that 4 ga changed out though to the alternator, you really want to make sure you're running the same size wire for everything. So if you're running 1/0 to grounds, run 1/0 to the alternator. Same with the other battery if you do put it in. Run 1/0 ga to the battery and since you only have one amp you can run a 4ga line from the second battery to the amp, just make sure you fuse that 4ga wire to the amp. You could also run a 1/0 ga from the second battery to the amp, but chances are you'll need a reducer cause the amp probably only takes a 4 ga input. But from that second battery to the amp, 1/0ga is really not necessary. Either way, again, make sure you fuse it.

I think that you'll run into alternator issues down the road if you run the second battery though. Unless you're planning on running a H/O alternator in the near future. It's just alot of load for that OEM alternator to be charging both batteries.

Again, I really don't think you need another battery, I'd save that money and upgrade your alternator with it. The only reason I'm running 3 batteries and a H/O alternator is cause I'm running enough power, capable of approx 4500 watts, and with all that the extra power is nice so the system runs more efficiently.

Hope all that helps.
 

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yeah i was definitely concerned about the alternator with having two large batteries. and yes it does alot thank you :) i think ill end up sticking with my new redtop for now and definitely get rid of the cap i will also try to get some more 1/0 gauge wire for the alternator. but thanks for the advice :D
 

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Discussion Starter #45 (Edited)

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Hey thanks for the DIY on the big 3. I have all the 0/1awg wire and fuses to do exactly what you did. My only question is when calculating what battery to get I decided on an optima and noticed you had the yellow top so I decided on that as well instead of the red top. This is the part # from optima for the battery I need when I enter in my year/make/model. (2010/civic/si) D51R (8073-167). It appears in your picture you're using a full size optima battery, should I do this as well? I assume you needed to modify the tray and what not.. Or will the smaller civic size replacement from optima be adequate? Currently I'm only running a single 1000rms amp but will eventually add a 4 channel amp, HIDs and an in-dash nav on top of this.

Thanks
 

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Im planning on doing the big three with my 09 civic.
Question: whats the propper way of removing the + alternator rubber plug
Question: since the rubber plug is gone (like in you pic), would and is there a concern that water could short something out?
Question: can i just buy a zero gauge "amp wiring kit" and use those wires for the big three? (saves money) - obviously i'd need an ANL fuse holder - or are there other ways to get good material (aka wires n stuff).
 

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Im planning on doing the big three with my 09 civic.
Question: whats the propper way of removing the + alternator rubber plug
Question: since the rubber plug is gone (like in you pic), would and is there a concern that water could short something out?
Question: can i just buy a zero gauge "amp wiring kit" and use those wires for the big three? (saves money) - obviously i'd need an ANL fuse holder - or are there other ways to get good material (aka wires n stuff).
I was able to still use the rubber cap. I cut just enough of the plastic off for the plug to fit then I cut a piece of the rubber cap off to make room for the wire..you can kinda see it in my posting 'those of you who upgraded...'
 

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So I did this last week and it seemed to help out with a DBW lag. The lag is still there but seems to be less. I skipped the fuse part for now since I can do that later. What size fuse to use?
 

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i ordered everything to do the big three on my SI and was looking at where the power comes off the alternator and i cant see any easy way to get to it at all. Any ideas?
 

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Connection #1: This is a piece of positive cable, run between the alternator output terminal (the nut on top of the alternator under the rubber boot) and the positive battery terminal. Ideally, you should fuse this wire near the battery, but many people forego this step.
if i do not use a fuse.. what will happen ? what is possible ?
 

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if i do not use a fuse.. what will happen ? what is possible ?
My guess is nothing will happen if you don't use a fuse as long as your wire insulation does not melt and make contact with the frame/body. Worst case scenario if something does happen, it would be a new alternator or battery. I believe in older cars, the battery was connected directly to the alternator with no fuse but then those cars didn't have electronics...
 
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