battery bypass issues, 12v in rear bank, 3.6v under hood.

[Wasteland_Audio]

So my front battery took a shit on me this morning and I need to get it running ASAP so I can make it to work tonight. As I have a battery bank in the back of my 04 Burban I figured I could just bypass the front battery and be fine. However, after disconnecting all the wires from the front battery and hooking the rear runs directly to the factory terminals I am somehow only seeing 3.6 volts at the front connections and 12 volts at the rear. How is this possible as there are 2 1/0 runs coming directly from the rear positive and negative bank?

[ShadeTreeMechanic]

Do you have a fuse blown somewhere?

[ShadeTreeMechanic]

Make sure the grounds are still connected.

[Wasteland_Audio]

Do you have a fuse blown somewhere?

Not one that's super obvious. Everything was working perfectly last night and then this morning the rear bank was at 11.9v and the front battery was 8.8v. How that is i have no idea as they are connected with 2 1/0 runs. I thought batteries always balanced themselves? But anyway here is a diagram of how i have it wired now to get 3.6v under the hood.

[ShadeTreeMechanic]

The way you show it, it would be impossible to get a different reading up front. This assumes all of the connections are good. If you had a bad connection, it could have enough resistance to show a lower voltage. Maybe you could check all of your connections with a volt meter? You should be able to find it if you check everything.

[Wasteland_Audio]

Ok so update. i hooked everything back up to the way it should be, checked all my connections and grounds, and basically made sure it was hooked up perfectly. As i hooked it all up i made sure to monitor my voltage after each connection. The front battery was resting at 11.9 volts all the way up until i made the last positive connection, battery + to the starter/fuse box (factory terminal). Immediately after making this connection the voltage dropped to 9.6 volts, i removed it and the resting voltage crept back up to 11.9. Any ideas on what would cause this?

[ShadeTreeMechanic]

Maybe there is something that goes through the factory fuse box that is turned on or consuming power? You could pull all of the fuses out and re connect. Insert fuses one at a time to find the circuit drawing power.

[Wasteland_Audio]

I'll give it a try. I checked all the fuses with the multimeter and they all came back good so I guess thats the next step. I just can't think of anything in my vehicle that could draw that much power tho

[ShadeTreeMechanic]

Yeah that does sound like a lot of power.

[Kyblack76]

sounds like something is going to ground, like a winding in your starter. Feel the starter, is it hot? Remove hot to starter, and re hook up ever thing, look inside fuse block.......... something, is basically grounded out, pulling your load down.