Aux battery isolate/bypass without delete

[ASSFROW]

Hello everyone,

Is there a way to keep the Aux battery, but isolate or bypass what causes it to drain the main battery?

I don't mind having it or the ESS, but I don't want the dreaded death by Aux battery.

Thanks, Gary

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[AndySpill]

Hi Gary:

Simply disconnecting the cable on the negative post of the main battery whose distal end connects, unseen, with the negative post of the tucked away Aux battery will make it electrically impossible for the Aux battery to effect or be effected by anything else in the vehicle.

Two factory cables find their way to the negative post of the main battery. One has as its distal end the ground connection on the passenger's front panel under the hood. Please leave this cable connected. It is the other cable that you should remove from the main battery's negative post and insulate its metallic end with electric tape.

In concert with this step I recommend that you remove Fuse 42 from the Power Distribution Center (PDC). This step will (only) prevent the Power Control Relay (PCR) from being energized: a switch that when provided electrical current will separate the main and Aux battery: something that only happens for an instant at startup to test the Aux battery, and during ESS events.

I don't recommend running ESS events, otherwise not only entirely doable, but perhaps more likely to happen with the Aux battery disconnected. I say more likely because with the cable and fuse pull this pre-crank test I speak of, which normally tests the Aux battery for ample power to run ESS events, will now silently occur against only the main battery, perhaps tricking the vehicle into thinking that its ESS battery (really its main) has ample power to run ESS events.

Countless other vehicles run ESS with one battery and the two battery factory setup in the dual AGM battery JL probably has more to do with addressing voltage sensitive electronics in the entertainment system than anything else, but I just can't in good conscience recommend the proverbial ESS event in the middle of a snow storm, at a high speed left turn, that robs the main battery of the very power it needs to crank the engine with such a one battery ESS JL setup.

If you don't disconnect this fuse your first attempt at cranking (speaking of all post 2018 dual AGM battery JLs) will likely fail, the second and subsequent succeeding provided your main battery has ample power. Once cranked (again if you don't remove this fuse) expect the dash to throw an ESS off light on. Sounds perfect right? The problem is that this light is seen by forum experts as a sign of problems that if always illuminated may fail to disclose a troubled situation.

(With the fuse pulled) You can turn off ESS by pressing the button or buying aftermarket tech to do this for you.

~~~~~~~~~~~~~

If for some reason you wish to keep the Aux battery charged the easiest way to do this is to place a charger on the main battery's positive post (that's right, I said main battery) and the cable you just removed, sans electric tape. This will charge only the Aux battery.

I see little benefit to removing it. As a sealed AGM battery its unlikely to cause leaking issues anymore than as residing closest to the ground, would suck leaking likely affect other vehicle components.

 

[ASSFROW]

Hi Gary:

Simply disconnecting the cable on the negative post of the main battery whose distal end connects, unseen, with the negative post of the tucked away Aux battery will make it electrically impossible for the Aux battery to effect or be effected by anything else in the vehicle.

Two factory cables find their way to the negative post of the main battery. One has as its distal end the ground connection on the passenger's front panel under the hood. Please leave this cable connected. It is the other cable that you should remove from the main battery's negative post and insulate its metallic end with electric tape.

In concert with this step I recommend that you remove Fuse 42 from the Power Distribution Center (PDC). This step will (only) prevent the Power Control Relay (PCR) from being energized: a switch that when provided electrical current will separate the main and Aux battery: something that only happens for an instant at startup to test the Aux battery, and during ESS events.

I don't recommend running ESS events, otherwise not only entirely doable, but perhaps more likely to happen with the Aux battery disconnected. I say more likely because with the cable and fuse pull this pre-crank test I speak of, which normally tests the Aux battery for ample power to run ESS events, will now silently occur against only the main battery, perhaps tricking the vehicle into thinking that its ESS battery (really its main) has ample power to run ESS events.

Countless other vehicles run ESS with one battery and the two battery factory setup in the dual AGM battery JL probably has more to do with addressing voltage sensitive electronics in the entertainment system than anything else, but I just can't in good conscience recommend the proverbial ESS event in the middle of a snow storm, at a high speed left turn, that robs the main battery of the very power it needs to crank the engine with such a one battery ESS JL setup.

If you don't disconnect this fuse your first attempt at cranking (speaking of all post 2018 dual AGM battery JLs) will likely fail, the second and subsequent succeeding provided your main battery has ample power. Once cranked (again if you don't remove this fuse) expect the dash to throw an ESS off light on. Sounds perfect right? The problem is that this light is seen by forum experts as a sign of problems that if always illuminated may fail to disclose a troubled situation.

(With the fuse pulled) You can turn off ESS by pressing the button or buying aftermarket tech to do this for you.

~~~~~~~~~~~~~

If for some reason you wish to keep the Aux battery charged the easiest way to do this is to place a charger on the main battery's positive post (that's right, I said main battery) and the cable you just removed, sans electric tape. This will charge only the Aux battery.

I see little benefit to removing it. As a sealed AGM battery its unlikely to cause leaking issues anymore than as residing closest to the ground, would suck leaking likely affect other vehicle components.

Thanks for the info. I would prefer not to disable anything, just prevent the Aux battery from draining the main battery if that's possible.

 

[jeepingib]

Thanks for the info. I would prefer not to disable anything, just prevent the Aux battery from draining the main battery if that's possible.

You can try to just take off the negative terminal on the main battery that goes to the aux battery, but it will give you a check engine light unless you pull F42 fuse. I pulled it and just put it in one of the spare slots. If I ever wish to go back, it's as simple as putting the fuse back in, and connecting the ground.

 

[AndySpill]

Thanks for the info. I would prefer not to disable anything, just prevent the Aux battery from draining the main battery if that's possible.

I've though about this too. I suppose somewhere out there that there's a relay that could open the connection between the two batteries if their collective voltage as a pair drops below some threshold.

My solution has been to trickle charge both batteries an option made easy for me given that I already have a roof rack upon which to place solar panels to effect same and I park outdoors.

There's always this: it's good but not cheap: https://www.cascadia4x4.com/collections/jeep-vss-system-hood-solar-panels

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