Aux Battery or TP2 upgrade

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Dec 23, 2021 | 3:03 PM

#21

Meller

CF Beginner

Joined: Dec 2021

Posts: 3

Likes: 0

Quote:

Originally Posted by omandave

Hi there Meller, and welcome to my original post...
The main relay that is added near the "hood support rod/piston" (12135194 -RELAY; AUX BAT Qty 1) is what does the make/break action of the aux battery.

Part of the installation adds the "running" signal from the fuse panel... Also if you look at the last photo that was posted by "InTheBurbs" there is s secondary relay built into one of the aux harnesses that is also installed.

When the key is in the off position, the batteries are separated.
when my key is turned to the run position, i can here an audible click(clunk) from the main relay, connecting the two batteries positive wires together.
When I turn the key to start, i can audibly hear the main relay disconnect again.
The signal comes from the new pins added to the underside of the fuse block. It adds a positive "sense signal" (power when in "run") that feeds the grey relay to kick the main aux relay to close the batteries together.

When the key is off, or at start position there is no power sent to the inline relay(grey one closer to mega fuse holder)
So the relays are the magic behind the "wire loom"

Hope that helps to explain the real world use of the TP2 add-on for you.

I have zero regrets for installing this into my 2009 suburban.

Cheers and Happy Holidays

so I think the reason that I was confused is due to thinking that the aux battery carries the load when the ignition is in the off position. After looking through all of this again, it appears that the primary battery is what carries the load when the ignition is in the off position and then the aux battery is connected in parallel when the ignition is turned on. Am I grasping this correctly now?

Dec 24, 2021 | 10:57 AM

#22

omandave

Thread Starter

CF Junior Member

Joined: Jul 2013

Posts: 40

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From: Skagit Valley, WA

Quote:

Originally Posted by Meller

Hi Meller,
I think you "got it".
The Primary Bat (passenger side firewall) carries the main loads still. This one is also used to singlehandedly start the vehicle. The Aux Bat (driver side front) can be used to assist in "jump starting" with the use of jumper cables aux+ to main+ which was my reason for installing this thing. (Stranded wife with dead main due to DVD player use with engine off...)

The diagrams we're found via some old GM up fitter pdf finds i located online years ago. The police/service vehicles had the dual battery setup to support all of the extra lights,computers, power needs etc...

As for how the grey relay functions... It is built in to the 25862351 -CABLE; POSITIVE Main to AUX BAT Harness.

I just provided the "signal wires" needed from the underside of the fuse block as part of the write up(following paragraph)

There is a plastic relay on cable 25862351 which has wires connected to the large relay (12135194) and a connection plug with three wires (red, orange and black). The plastic relay is used to activate relay 12135194 whichis what isolates the aux battery from the charging system. I chose to use part 15305801 which is a four wire plasticconnector that plugs into the relay connector. It has four white/grey wires. You'll need to match up the wire colorsto the relay and remove the fourth wire. I ran three wires inside the 3/8” wire loom. I used the original factory wireclamps to run it next to the new main battery cable all the way to the fuse box. On the X2 connector of the underhood junction box, using terminal connectors (13525970), the red wire goes to A5 and the orange (green fromradioshack) wire goes to B4. The black wire goes to ground on the vehicle. I grounded it directly to the engineblock where I grounded cable 25876897.

That was the custom fabrication that was needed to correctly hook up the grey relay, which triggers the big Aux Relay...
I don't know that I could fabricate the OEM harnesses and get the system to work properly...
My intention had always been make it a "sleeper" vehicle. Aka, if you did not know that the aux battery was not a factory option, looking under the hood you would think that it was built with the Aux Bat package.

Cheers and if you tackle it, wishing you Success.
Happy Holidays.