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Auxiliary Battery Install - OEM Look without the Headache

TXSZ66AVLANCHE

Full Member
Joined
Oct 26, 2009
Messages
634
Location
DFW Area
Just got done installing the auxiliary battery in my 04 Z66. I wanted the install to look OEM but didn't want the headache of figuring out all the cables, wires, junction box, and relays. Here are the parts I used to install.

GM Dealer:
RETAINER,AUX.BATTERY HOLDDOWN 356668
TRAY,AUX.BATTERY 15246518
SCREW, BATTERY 11509853
CABLE, NEGATIVE 15321212

Summit Racing
BATTERY CABLE KIT, 2 GAUGE, SIDE POST SUM-G1198

eBay
STINGER GM SIDE POST PLATIMUN BATTERY TERMINAL STP55308

O'reilley Auto Parts
1/2 Diameter convelated conduit 12 feet

Installing the AUX battery tray is simple and uses existing hardware from the fender brace, the upper fender brace will need to removed permanently. The battery you install is up to you, I went with a Continental battery since it matches my primary battery.
AuxBattery001.jpg

Ground Cable
The ground cable I used is actually the same exact cable that is used on the primary battery, I chose this cable for several reasons #1 The length of the cable is perfect! #2 There is heat shield installed on the lower portion. Grounding the cable is done on the forward top bolt for the AC compressor, since there is heat shield on the cable the close proximity to the right side exhaust manifold will not be an issue. There is an extra wire (small) that is meant as a chassis ground when used on the primary battery that is not needed and can be removed from the cable if desired.
AuxBattery002.jpg


Positive Cable
The battery cable kit from Summit Racing comes with a short 12 inch ground cable that is not needed (ordered just for the positive cable) the positive cable is VERY FLEXIBLE and unlike the OEM cables is very easy to work with, install the conduit on the entire length of positive cable before you start routing the cable in the engine bay. If you still have the OEM intake and air box this routing will not work for you.

The positive cable is run between the coolant reservoir and battery and secured with a p clamp (p clamps comes with Summit kit) that attaches to the stud for the coolant reservoir. There are several holes that already exist in the fender that can be used to install retainers to route the cable and make a clean, professional looking install. Next the cable runs across the front of the radiator,there are many holes on the top of the radiator to install retainers in order to keep the cable off the radiator. Keep in mind that there is allot of extra cable and it either needs to be shortened or you can take up the extra space with your routing. I chose to route the cable between the driver side headlight and turn signal lamp and bring the cable in between the battery and driver side fender. FYI..all of the positive cable is hidden and is not visible when installation is complete.
AuxBattery003.jpg

Battery Terminal Connection
I am using a stinger GM side terminal temporarily until I can find a more OEM looking method to install. These are very easy to install, the OEM stud is removed and the Stinger terminal is installed in its place. The stinger terminal has a hole drilled in the center with a bolt to attach the cable from the AUX battery. Updates will follow when I piece together a better method to connect the AUX battery to the main battery.
AuxBattery004.jpg

Notes/Comments
Will add more pictures soon
AUX battery is not isolated
Battery gauge shows 13 volts without the engine running!
Battery gauge reads normal range with engine running.

 
So I have to ask why did you install dual batteries. ???
 
Why else does a person do mods? Because one mod leads to the next! The next mod is a electrical outlets in the bed and center console (power inverter will be under back seat) I use my truck for work and the outlets will come in handy for small jobs when dragging out a generator is not practical. I decided that isolating the batteries was not going to be necessary in my case because I don't power accessories like radios, subs, amps with the truck off.

Did this answer your question?
 
Yep it answered my question. Good luck with it.
 
Have you ever thought about a bigger alternator, dual batteries are not going to help you.

JMHO :dunno:
 
MS03 2500 said:
Have you ever thought about a bigger alternator, dual batteries are not going to help you.

JMHO :dunno:

He's right..  when the engine is running, it's the alternator that powers the world...  only when the engine is off will the other battery help ya.  But, the additional battery will let you power that stuff with the engine off for a longer amount of time, should you want to save gas.
 
Eskimo be prepared for him to blast us. >:D

We are just trying to help him.
 
I was leery about buying this from eBay, so far its been good.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=350296834361&viewitem=&sspagename=STRK%3AMEWAX%3AIT
 
My dual setup has been great. More than once I had a dead main battery and just flip a switch and I am on my way  :love: On now keep a battery tender on the main since I don't drive tha AV as much as I used to  :D
 
TXSZ66AVLANCHE said:
Just got done installing the auxiliary battery in my 04 Z66. Installing the AUX battery tray is simple and uses existing hardware from the fender brace, the upper fender brace will need to removed permanently.
AuxBattery001.jpg


Very, very nice post!

Just one correction... the upper fender brace doesn't necessarily need to be removed permanently.
 
Too late for me... I already cut the portion by the firewall off. Where did you get the curved brace? I will be doing the same setup with power inverter in my Suburban.
 
You can still fit a full size Group 34/78 (approximately 7 3/4" tall) UPRIGHT in the factory tray, using the factory battery tray, cleats and tie-down bolt/block, and still have your fender to firewall brace.  Here is an example:

normal_0043.jpg

 
I found the new GM factory battery tray (for the diesels) to be suprisingly thin and tinny.  It also was a right angle stamping that did not have the diagonal gusset, nor did it offer the angular reinforcement that the battery-less factory lower brace had.

The GM factory battery tray is supposed to substitute for BOTH the upper curved AND lower angular fender-to-firewall braces, as well as support a 70 lb battery at the same time, all while being stamped out of THINNER guage thickness metal... no thanks, not in the front of my vehicle.  I wanted a little more metal upfront to bend and absorb crash energy before crushing the cabin, as that is wear my darlin sits.

I ended up using all three factory braces simultaneously in my installation.  I nested the original lower fender to firewall brace with the diagonally oriented gusseting, thicker metal, and larger firewall contact base underneath the new GM factory battery tray.  I mounted the battery using the factory hold down cleats and follower block.  I then modified the passenger side curved fender brace, and reinstalled it over the top using the original factory hardware.

The trick was clearing the battery, clearing the hood, clearing the hood hinge mechanism, the clearing the postive top post of the battery, clearing the forward top edge of the battery, clearing the fender side edge of the battery, and clearing the negative top post at the firewall...  all with enough clearance under the battery to not only accomodate the factory insulation, but another layer of insulation on top.

The top foam battery insulation was installed to record witness marks in twist ditch manuevers, to monitor how much vehicle twist between front and rear axles on different planar angles would induce a fender to firewall deviation so great as to make the brace contact the top of the battery.  I've tested this off road and on road, with the rear axle on a declined surface while the front axle was on an inclined surface, with the vehicle angle diagonal to both surfaces, to induce as much twist in the body as might be attained in any plausible operating condition, with no witness marks.  The brace continues to clear the battery and the hood at all operating angles.

Meeting all these clearances and still having a strong brace was not easy to design,  let alone commit to fabricating, given that I reused the original part and told myself that I would do without this brace altogether if I made a mistake that forced me to buy another one.  But obviously, it is doable.  And I didn't have to buy a second brace to do it.

For the factory look, I matched the radius bends and distances of the radiator de-gas bottle from the fender, so there is one continuous clearance line of space between fneder and battery that matches all compound angles that slope everywhich way but loose.
 
First very nice write up in your 1st post!  (y)

I have a small inverter mounted under the rear seats I use to run tools. With the engine off, I can only get about 60 % of the rated output. With the engine on, I could run a Makita roto hammer with a 12" 5/8 bit to drill though 6 inches into road. (made 15 holes per speed bump). I can also run a 1/2 drill, but again only while the engine is running. My inverter is only 400 watts so you may have different results with your setup. I think you would get better benefits just using your 2ND battery isolated as a back up or a seperate load.

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To those critical of dual batteries...

After four years now with an auxiliary battery, I can report that it has saved me quite a few times.  Being able to jump start oneself is very convenient.

Turned out, my main batter had a fault in the side post, which is why it went dead so often, but still tested great on the top terminals.  But before learning that, the auxiliary battery was called to the rescue more often than I ever imagined it would be.

Not necessary, as there is always Triple AAA... but why wait for them when there is room under the hood to be more self reliant?

Got my main battery replaced under warranty, so maybe I won't need the auxiliary as often now.  But it is still nice to have the option of running a charger for hours if necessary, without worrying about the battery being dead.  With the batteries separated, the probability is twice as high for one of the batteries to get the engine started.
 
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