3.6L ESS Aux Battery Bypass

Eloib

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What voltage differential do you guys see when the Aux ESS is dead? I woke up today and both my batteries were dead (5.5 V and decreasing). I think some water might have shorted my winch creating a ghost power consumption, along with potentially a 12V charger left plugged inside the vehicle.

I unplugged both and jump started. After driving for a while to get my batteries at a better state of charge, I observed about 80mV of potential differential between N1 and N2.



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Jebiruph

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That's a test I came up with to verify normal operation with the batteries in parallel. For me, it's always been 0, but with your batteries in a state of charging, a .08v difference is probably OK. A large voltage difference would mean they are not in parallel, which is only supposed to happen when auto stopped.
 

Hgrace

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The difference with the JL is the existence of two batteries. Not to say that your system wouldn't be up to the task, but the additional power needed to start a larger engine is probably less than the additional power needed to over come an additional drained battery. Both drained batteries will be competing with the starter for power up to a point. Eventually they will be charged enough for most of the power to go to the starter.
Sorry.
Been in the electrical industry 40 years.
Own 9 trucks. Jumped everything possible.
Have had an ESS/ BSG Hybrid over 10 years and 120k miles. Tge dual battery is not to crank the mighty 3.6 liter Jeep engine but to ensure inboard electronics are not drained completely. Have you followed the power schematics on this and other forums?
 
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Jebiruph

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What would be awesome is if someone figured out a way to isolate the batteries in such a way that you can run accessories on one battery with no fear of killing the other, so you can easily start your rig if one dies...without having to run an aftermarket dual battery setup. It doesn't seem there is a way, currently to do this. If you run a fridge without starting the rig, it will eventually kill both batteries it seems, would be nice to make that NOT happen.
If you disconnect the Aux battery ground cable form the Main battery terminal, that should isolate it from the system so it won't run down. The problem is trying to jump start from the Aux battery with a drained Main battery still connected, as that will put additional load on the Aux battery. After you reconnect the Aux battery to the Main battery terminal, removing that terminal from the Main battery would isolate the drained Main battery from the system. After starting, you would have to reconnect the Main battery terminal while running.

In brief, disconnect Aux ground before running accessory. When done, reconnect the Aux ground. If the Main battery was severely drained, disconnect Main battery terminal before attempting a start from the Aux battery.
 
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Jebiruph

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Sorry.
Been in the electrical industry 40 years.
Own 9 trucks. Jumped everything possible.
Have had an ESS/ BSG Hybrid over 10 years and 120k miles. Tge dual battery is not to crank the mighty 3.6 liter Jeep engine but to ensure inboard electronics are not drained completely. Have you followed the power schematics on this and other forums?
No need to apologize.
So I walk up to a JL with both batteries drained and connect my jumper leads to the Main battery. The power applied to the Main battery to crank the starter will also be charging the Main battery at the same time. Since the Aux battery will be connected electrically in parallel with the Main battery, that power will also be charging the Aux battery. At least that's how I see that it works, but would sure like to hear any evidence you have to the contrary. Detailed information on the system is pretty scarce.
 

NFRs2000NYC

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If you disconnect the Aux battery ground cable form the Main battery terminal, that should isolate it from the system so it won't run down. The problem is trying to jump start from the Aux battery with a drained Main battery still connected, as that will put additional load on the Aux battery. After you reconnect the Aux battery to the Main battery terminal, removing that terminal from the Main battery would isolate the drained Main battery from the system. After starting, you would have to reconnect the Main battery terminal while running.

In brief, disconnect Aux ground before running accessory. When done, reconnect the Aux ground. If the Main battery was severely drained, disconnect Main battery terminal before attempting a start from the Aux battery.
Thats not something anyone is going to do on an ongoing basis...but if someone put out a kit that had an isolator that can do this automatically, they would make a nice chunk of change.
 
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Jebiruph

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Thats not something anyone is going to do on an ongoing basis...but if someone put out a kit that had an isolator that can do this automatically, they would make a nice chunk of change.
Genesis offroad is working on something for SEMA.
 
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Jebiruph

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ess bypass simple 2a.PNG


edited 1/12/19 with updated diagram

In case the other diagrams aren't clear, here's a simplified diagram to emphasize how the batteries are connected in parallel through the PCR. A bad Aux battery seems to cause issues with the Aux battery powered systems, this shows the bypass jumper connecting the Main battery to the Aux battery powered systems.
 
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Oakwolf

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Sorry i am completely new at this kind of electrical knowledge, but somehow i feel that this thread is super important for what i intend to do with my JL. If i am at my shack in the cliffs (no service whatsoever possible), and the aux battery depletes...what can i do? I am concerned that i would be left stranded over there. Back then we could simply bring an extra main battery, but in this case...should i bring an extra "aux" battery?
 
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Sorry i am completely new at this kind of electrical knowledge, but somehow i feel that this thread is super important for what i intend to do with my JL. If i am at my shack in the cliffs (no service whatsoever possible), and the aux battery depletes...what can i do? I am concerned that i would be left stranded over there. Back then we could simply bring an extra main battery, but in this case...should i bring an extra "aux" battery?
Several weeks ago someone asked what to take over-landing and I said an extra Aux battery, but that was before I tried the Aux battery bypass shown on the first post. I didn't drive with the Aux bypassed, but it started no problem. Equipped with a jumper similar to what I used, I would take an extra full size and not worry about the Aux, but you may want to drive around with the Aux bypassed to make sure you're good with it. The other thing I would do is any time I was parked for an extended period of time (over night?), I would disconnect the Aux battery ground cable from the Main battery negative terminal. That should prevent both batteries from draining at the same time. I would replace the regular nut with a wingnut to facilitate easy removal.
 

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Several weeks ago someone asked what to take over-landing and I said an extra Aux battery, but that was before I tried the Aux battery bypass shown on the first post. I didn't drive with the Aux bypassed, but it started no problem. Equipped with a jumper similar to what I used, I would take an extra full size and not worry about the Aux, but you may want to drive around with the Aux bypassed to make sure you're good with it. The other thing I would do is any time I was parked for an extended period of time (over night?), I would disconnect the Aux battery ground cable from the Main battery negative terminal. That should prevent both batteries from draining at the same time. I would replace the regular nut with a wingnut to facilitate easy removal.
If i understand correctly, with a kit such as yours, we'd be back to simply needing an extra main. It's really interesting. That said it looks rather simple to install and uninstall, but just for the sake of the discussion, i wonder if that setup could be kind of permanently fixed and turned off or on as needed.
 
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Jebiruph

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If i understand correctly, with a kit such as yours, we'd be back to simply needing an extra main. It's really interesting. That said it looks rather simple to install and uninstall, but just for the sake of the discussion, i wonder if that setup could be kind of permanently fixed and turned off or on as needed.
Yes, you can remove and replace the fuse to turn it off and on. I do not plan on running mine permanently, will keep it in the glovebox with wingnuts to install as needed.
 

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I personally hate having both batteries, you would think the engineers could design it to run off one
 
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I personally hate having both batteries, you would think the engineers could design it to run off one
They did, the first ESS that is still used on the Cherokee is one battery. The two battery ESS is the new improved version.
 

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If you permanently disable ESS, can you get rid of the Aux battery?
Can you leave the bypass mentioned here in place and get rid of the Aux battery?
Sorry if it is a dumb question.
 

                           
























































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