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tast101
05-12-2009, 07:39 PM
Good info, figured I'd bring it over.

Well, installed a second battery this weekend, so here is the write up for the installation. Only thing is, some of you may be disappointed, as my wife had the camera when she was out, so I was unable to take pics during the installation. But i did manage to snap some after shots when she she returned home.
I'm using the aux battery to help power the high current stuff such as my 3000 watt power inverter, 5000 watt mono amp, etc. Right now I'm using the same cca/rc rating battery I had laying around and will be upgrading to Optimas later.

Parts
1. You will need a way to mount the new battery. Probably the easiest way to do this is to get a stock replacement battery tray with the retainer and retainer bolt.
2. Battery Isolator/relay. This will prevent the main battery from draining while the engine is off and your accessories are running off your aux battery. Note: If the key is in the acc position, the stock electrical system will continue to run off the main battery. Also, in the ign position, the isolator contacts are closed and power will be drawn from both batteries. In this instance, you will get power from both batteries, theoretically doubling reserve capacity.
3. Cables to connect the main battery to aux batt. I used about 12 ft of 4 gauge to run from positive to positive and two feet for ground.
4. About 14ft. of 18-22 ga. wire to activate the isolator. The isolator needs to be connected to a source that will turn the relay on while the eng is running so both batteries will charge.
5. Sidepost battery extender terminals(3), found at most car audio shops.
6. 4 ga. ring terminals, (6)
7. 18-22 ga. ring terminals, (3)

Tools
You will need an assortment of sockets, cordless drill/screwdriver with #2 phillips bit, asst of open end wrenches, digital multimeter, solder and soldering torch (or small hand-held propane torch if available).

Here are some pics to show the location of the battery and isolator, cables, etc.
http://i227.photobucket.com/albums/dd269/jkmotorsports/DSC05771.jpg

http://i227.photobucket.com/albums/dd269/jkmotorsports/DSC05768.jpg

Here is the cable routed in the front:

http://i227.photobucket.com/albums/dd269/jkmotorsports/9d19e351.jpg

Battery Isolator and fuse/fuseholder
http://i227.photobucket.com/albums/dd269/jkmotorsports/DSC05767.jpg


1). First, you will need to remove the fender to cowl brace on the passenger side near the hood hinge. There are four bolts; two attached to the cowl and the other two on the fender.
2). Mount the new battery tray in the area below the brace, on top of the fender well. There are no mounting holes, so you will need to screw the tray down with some self-tapping screws. Or you can remove the front wheel to drill new holes and use nuts/bolts to attach the new tray.
Set the new battery in the tray and secure.
3). Find a suitable place for the battery isolator. I mounted mine on the firewall, right above and to the left of the a/c accumulator. Be sure placement does not get in the way of the new battery. You can attach this with some self-tapping screws and your cordless driver:

http://i227.photobucket.com/albums/dd269/jkmotorsports/DSC05764.jpg

4). Now, you will need to prepare the new cables. Cut about 1 1/2 feet off the 12 ft cable. You should now have about 10.5 ft of cable, one 1.5 ft section, and about two ft for ground. Attach each end of each cable with the 4 ga ring terminals. I soldered all my ring terminals using a propane torch and solder, then used heat shrink to insulate the connections. I used a propane torch because it heats the larger terminals and cable much faster for the solder to flow better. You will also need to attach a smaller ring terminal to one end of the smaller ga. wire used to activate the isolator. Next, cut off about 2 ft or so from one end of this wire. Attach the other two smaller ring terminals to each end of this shorter wire.
5). Attach the shorter section of 4 ga wire onto one terminal of the battery isolator. Follow the instructions that came with your battery isolator as to which terminals are which. They should all be the same, with two large posts and two smaller posts. The cable will attach to one of the larger posts (either one). Next, attach the other end of the cable to the positive terminal of the new battery using one of the sidepost battery terminals. You can also attach any cable you may have for your accessories (amp, etc) now.
6). Attach the longer run of 4ga cable to the other large post on the isolator. Also, attach the smaller 18-22ga wire on one of the smaller posts of the isolator (again, either post). Route this wire along with the cable down the passenger side, across the front over the fan shroud, and to the main battery. If you have split loom available, slip the loom over the cable and wire before routing. Be sure to route the wire as neatly as possible and as not to interfere with the airbox removal or any other part. Secure the cabling with wire ties, cable mounts, etc. as neccesary.
7). Now connect the end of the 4ga cable to the positive terminal of the main battery. To do this, you will need to remove the stock terminal and replace it with one of the new extended terminals so that you can fit the new cable on. Secure and tighten the post.
8). You will need to use a test meter to find a 12V source that powers on with ign only. The end of the smaller gauge wire will attach to this source. I attached to an ignition wire coming from the fuse block harness. You can simply attach to an appropriate fuse in the box with a fuse tap, but the preferred method is to splice into an ign source wire and solder.
9). Now, connect the short length of the smaller gauge wire to the last small terminal post of the isolator. Leave the other end loose for now.
10). Connect one end of the ground to the negative terminal on the battery using one of the new sidepost terminals. Route this and the loose wire from the isolator to an existing bolt on the body (fender, firewall, etc.) and connect to ground. Option: I also used another length of cable from the battery ground to the frame to ensure lowest possible voltage loss from battery to chassis.
Go through and make sure the cables, battery, all connections, isolator, etc. are all secure. Test operation of the isolator by turning the ign key to the ignition position. You should hear the isolator click on and off when the key is turned from ign to off positions.

Option: I also upgraded the stock 8ga wire from the alt to main battery with a new 4 ga wire, and added a beefier ground cable to the main battery.

I hope this is informative. These are general guidelines, as wire gauge, parts, and placement may be different depending on specific application. And please feel free to chime in if it's obvious I missed anything (long post, so I might have gone off track somewhere. I've already edited 4Xs)

T3rry
08-11-2009, 01:58 PM
Thanks for this post, it's very helpful, i just did the same install, the only thing i did differently was that i put the battery sideways (compared to how yours is) just because mine was an optima red and i have top posts on it, so i couldn't stuff it under the back there like you did. It does rub the AC lines, but it should be fine.


also i didn't bother with the isolator and stuff, i may do that when/if i can find a suitable deepcell battery.

and i like the fact that i have a backup battery for my alarm/starter :D

sparg93
01-25-2010, 11:36 PM
--

Dvldogyut
09-09-2010, 01:38 PM
Did this on my old 06 silverado, about to do it on my 01 hoe too.

B0$$MAN
01-04-2011, 08:15 PM
Where can I get the battery tray and bolt and holders?

OmarR
01-08-2011, 09:54 PM
Where can I get the battery tray and bolt and holders?

Dealer or yard. Here are the GM #'s:

Battery Tray 15246518
Hold down retainer 356668
Hold down retainer bolt 11509853

urnamehere
01-11-2011, 10:06 PM
heres my old set up i helped make the tray and chop and lift up the fender brace up
http://i260.photobucket.com/albums/ii11/elweys/1118081302-1.jpg

Tahoewhat
02-20-2011, 10:06 PM
i know this is old, but its a sticky, so maybe helpful.. But going to try this out this weekend. But i kind of understand all of it, but on the isolator, where are you guys hooking up for the ignition part of the isolator?

d3adpool
02-26-2011, 10:52 AM
Dealer or yard. Here are the GM #'s:

Battery Tray 15246518
Hold down retainer 356668
Hold down retainer bolt 11509853

thanks, i've been looking to do this, just never could find a tutorial.

urnamehere
03-22-2011, 04:07 PM
i didnt use a isolator

TWITCH101
01-18-2012, 11:51 PM
Is the battery tray just a normal drivers side tray that you use for the passenger side? or is it a different tray from another model like a diesel?

OmarR
01-19-2012, 09:01 AM
Different tray from the drivers side.

TWITCH101
01-19-2012, 04:16 PM
thanks Omar....Seems like you are on every thread around here...lol....so I should be able to walk into a dealer and be like "here is the number, order it" right? Or would taking my business elsewhere be a better idea?

OmarR
01-19-2012, 11:23 PM
thanks Omar....Seems like you are on every thread around here...lol....so I should be able to walk into a dealer and be like "here is the number, order it" right? Or would taking my business elsewhere be a better idea?

I hope my involvement is a good thing. :)

Yes, you can take that number to any dealer. I would see if you can get it cheaper online first.

TWITCH101
01-20-2012, 09:21 PM
What vehicle does the battery tray come from? I think it would be easier to search for it by vehicle instead of part number online.

---------- Post added at 08:21 PM ---------- Previous post was at 08:13 PM ----------

Is this the one I need? http://www.rmsautoparts.com/proddetail.php?prod=15246518

Rivieraracing
01-20-2012, 10:18 PM
I hope my involvement is a good thing. :)

Yes, you can take that number to any dealer. I would see if you can get it cheaper online first.

OmarR is the man, in case anyone didn't know already!!:Handshake:

TWITCH101
01-22-2012, 12:19 AM
Yea It seems Omar has done almost everything on these forums....

OmarR
01-22-2012, 06:45 PM
Thanks guys!

Yes, Twitch....the one you linked is the part you need.

I know it's not this forum, but I contributed to this thread:

Dual Batteries (http://z71tahoe-suburban.com/iboard/index.php?showtopic=20692)

TWITCH101
01-23-2012, 12:47 AM
Thanks guys!

Yes, Twitch....the one you linked is the part you need.

I know it's not this forum, but I contributed to this thread:

Dual Batteries (http://z71tahoe-suburban.com/iboard/index.php?showtopic=20692)

thanks, I think I'll order it asap....been wanting to do this for a while. Omar I have a question for you. So I'm driving down the road and come to a stop sign. right as I'm stopping I see my voltage meter drop significantly and my engine seems to want to stall. It only lasts a second or less and goes back to normal. doesn't do it every time just about 1 of of 4 times. could this be a bad ground?

bolo1g2
01-23-2012, 04:54 PM
I used Omar's write up when I did mine. It helped a lot.

vatahoelt
01-24-2012, 08:06 PM
i'm somewhat interested in doing this oem style. but even with a parts guy hookup, the price for everything is still pretty high. wowsers :eek:

I did have a question about the 2nd battery. How important is it to be the same as the main battery?

TWITCH101
01-24-2012, 09:18 PM
Bought mine from a dealer yesterday....they didn't have one in stock so they ordered....had it in less than 24 hours, and only cost me 35 after tax. I think that isn't bad considering everywhere I could find one online was averaging $30 plus shipping. Install was literally a bolt in. took about 10 min....thats counting the time it took me to get my tools out until the time I was done and had my tools put away.


I plan on trying to find a regular 12v battery that is shorter and will allow me to reuse the brace, I just really like the look.

I don't think the battery type will make a big difference but I could be wrong. I just don't see any relevance in brands, I mean, 12v is 12v and Current is Current no matter whose sticker is on the box. But thats my view.

bolo1g2
01-25-2012, 12:02 AM
From what I've read, if you don't run some kind of isolator/relay between the batteries, they need to be very similar. if you run an isolator/relay then you don't have to worry about the batteries being the same. i used a relay in my setup.

TWITCH101
01-25-2012, 12:15 AM
after doing a quick google search I discovered that its not recommended to use differenct chemistry batteries...I'm assuming alkaline and nickel???? Also an issue might be the type, deep cell and what not...don't want to get different types because one battery will drain the other down constantly, this causing premature death of one battery.

OmarR
01-25-2012, 11:07 AM
thanks, I think I'll order it asap....been wanting to do this for a while. Omar I have a question for you. So I'm driving down the road and come to a stop sign. right as I'm stopping I see my voltage meter drop significantly and my engine seems to want to stall. It only lasts a second or less and goes back to normal. doesn't do it every time just about 1 of of 4 times. could this be a bad ground?

Internet diagnosis can be difficult :)

Since it doesn't cost anything, I would definitely check your grounds and your battery connections to make sure they are tight.. Main grounds for the BCM and PCM are between the heads and the firewall, at the rear of the block. Yes, they are a pain to get to and you will need a long extension.

Is your accessory belt old? I would change that as well. It could also be somethng a little more such as the changing of fuel-to-air ratio (going from throttle to full stop) and maybe a tune-up is in order?

TWITCH101
01-25-2012, 05:26 PM
Also, headlights dim as well, and if I'm running my ac on high I can hear the fans slow down. I'll check my grounds when it warms up a little more.

How much does a tune-up cost? I got brand new plugs and wires.

WildBill
01-26-2012, 12:12 AM
I would disconnect the second battery and drive for a bit to see if the problem continues. It could be something like a weak Idle Air Control and not the electrical. i.e. the dimming could be because the rpm is dropping.

---------- Post added at 11:12 PM ---------- Previous post was at 11:06 PM ----------

On the battery topic, I would do matched as closely as possible. Both Lead-Acid, same brand, same CCA. CCAs may be rated differently by different manufacturers. If different batteries are used, one will discharge at a different rate that the other and one battery WILL try to charge the other. I wouldnt mix a deep cycle with a standard Lead-Acid, nor with an AGM or drycell.

TWITCH101
01-26-2012, 02:19 AM
Yea I'm def gonna match amps and type if i can....o think it will only be a big issue it its two completely opposite batteries.
And I only have one battery right now.