Question about the small battery

[Canucklesammich]

3.6 non-etorque engine. I just want to know (if anyone else knows) if that small battery designed for the ESS powers anything other than the starter. What I'd LIKE to do is install a diode on the positive side to eliminate any power going to anything else in the vehicle, then wire my dashcam into the small battery (obviously between the diode & the pos terminal) to use for "parking mode". This way, I use something existing I have no other use for & it would be a great aux battery that is already set up to constantly recharge. BTW, I have one of those modules that remembers the ESS "off" setting, so that's not an issue.

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[AndySpill]

I don't believe that the ESS/Aux battery powers anything but appliances in ESS events, aids in cranking the engine: cold or post ESS events (which you'll turn off,) and undergos a pre cold-crank test of its voltage. And while your diode should prevent appliances other than your proposed dash camera from pulling electrical current from it, that same diode--correct me if I'm wrong--won't prevent the movement of electrons into the battery (just out), for example, to charge it back up from the alternator when the engine is on.

But I'm thinking that you may also want install a normally open relay, energized (and therefore closed) when the vehicle is cranked, on the ESS/Aux battery's positive terminal, where such relay lies after your direct cable hookup to this battery's positive terminal to the dash camera positive (therefore unaffected by the relay's presence,) but before other (factory) cables.

I say this because as you may appreciate, your two batteries are connected, by factory setup, in parallel, at all times but an instant at engine crank and during ESS events, and the electrical current that you pull, small that it is, for your dash camera in parking mode (4-6 Watts I'd approximate) from the ESS/Aux battery, that then reduces the ESS/Aux battery's voltage in parking mode (with the engine off,) will cause electrical current to flow from the main battery into it, essentially making you use both batteries to power the dash camera in parking mode.

Maybe I've missed something in either my understanding of your intentions, or the dual AGM battery JLs vehicle's flow of current and setup.

If this approach proves interesting to you then consider tapping the same fuse in the Power Distribution Center, and by similar means, that Shane does for his Dual battery kit, for determining that the vehicle is on.

I would also hope that your dash camera would not be in parking mode longer than the time to drain the ESS/Aux battery beyond 50%: a metric controllable by most parking mode capable dash camera's voltage cutoff, and at around 12.0 volts, compared to its about 12.7 volt fully charge.

 

[Canucklesammich]

Awesome answer. Since right now, I don't put the cam in "park" mode due to possibly an excessive draw on an already questionable stock battery, this is only an added perk. My intention is to get some benefit from the small battery; otherwise I'll just do the "fuse 42 & neg. cable disconnect" to save the main. I see your point in the smaller battery draining the main if it gets too low...hadn't thought of that; nice catch. So if I have this right, the relay closes when the engine is on but opens when the engine is off, preventing the aforementioned draw from the main to the possibly depleted small one.Thank you very much for your time & knowledge, exactly what I was looking for.

 

[jeepoch]

@Canucklesammich,

As per Andy's post above, it sounds like the Genesis Dual Battery System is right up your alley. Really. It not only totally eliminates the AUX altogether, it gives you easy access to the two similar 'Main' sized batteries. Ultimate in available power and very well thought out.

I personally haven't (yet) invested in it for two reasons:
1. Way over-the-top expensive.
2. The six-cycle limit imposed to the ESS.

Of course I can manually rewire their system to make the 2nd large battery act like the little AUX, but then I refer back to item #1. Pretty high-priced AUX replacement.

However, after three sets of batteries replaced in four years, that would have certainly made a dent in the overall investment. This ESS design certainly does suck.

Also to Andy's response, the AUX contributes nothing to cranking the starter. It's only mission in life is to power the cabin electronics, lighting and fans during an ESS event.

Best of luck,
Jay

 

[AndySpill]

So if I have this right, the relay closes when the engine is on but opens when the engine is off, preventing the aforementioned draw from the main to the possibly depleted small one.

Yes, correct, spot on. You've fully and correctly stated why I feel the relay indicated. It is clear to me that you fully and clearly understand me.

 

[AndySpill]

@Canucklesammich :

As I think more about this approach I discussed I want to add the following caveat.

Either confirm that the relay I describe is closed BEFORE the vehicle does its pre cold crank isolation of the ESS/Aux battery, whatever fuse you connect it to

or just pull Fuse 42.

Here's why. Let's suppose the pre cold crank test of the ESS battery happens before my proposed, normally open relay is energized. If that happens the vehicle will find there to be no electrical current on the ESS battery, thanks to the Power Control Relay (PCR) separating the two batteries during the cold crank, and my normally open deenergized during the cold crank test of the ESS/Aux battery relay isolating the ESS/Aux battery from all else.

On early 2018's this will prevent cranking. On your later model JL the first crank attempt will fail but subsequent ones will go against the main battery, and provided this battery has ample cranking power the vehicle will crank, and the ESS system will be turned off by the vehicle and an ESS off light will get placed in the EVIC (dash): a letter "A" with near circle around it followed by an exclamation point.

I plead ignorance, once this happens, if the vehicle allows the ESS/Aux battery to be charged by the alternator: my concern. If it doesn't that battery won't have opportunity to get charged back up by the alternator from its dash camera current draw.

By pulling Fuse 42 the batteries will not be able to be separated, so even if my proposed relay gets energized after the pre-cold crank test of the ESS/Aux battery, such that no ESS/Aux battery is found, this pre-cold crank test will just happen silently against the main battery, the JL not even knowing so, because the PCR, a normally closed relay won't get energized by the Fuse 42 pull to be able to separate the batteries .

I hope that convoluted reasoning makes sense.

 

[Canucklesammich]

Jay- this was an idea simply to make use of an existing battery that I assumed wasn't being used since I had "disabled" the ESS. Since I'm only referring to adding the parking monitoring mode on a dashcam, it would hardly be worth the expense of the Genesis system. Andy- thanks for all the info/advice; I'm leaning now towards just pulling the 42 fuse & disc the neg lead. Please don't feel that you've wasted your time; if anything you've probably saved me from a lot of aggravation/possible expense with a project that SEEMED so relatively simple but, thanks to an overly complicated design (thanks, Jeep!), looks to not be worth the hassle. If I decide to try it out just to see if it'll work (since it's a '22 & the batteries are probably approaching replacement status soon enough), I'll let you know. You guys are the best.

 

[AndySpill]

Jay- this was an idea simply to make use of an existing battery that I assumed wasn't being used since I had "disabled" the ESS. Since I'm only referring to adding the parking monitoring mode on a dashcam, it would hardly be worth the expense of the Genesis system. Andy- thanks for all the info/advice; I'm leaning now towards just pulling the 42 fuse & disc the neg lead. Please don't feel that you've wasted your time; if anything you've probably saved me from a lot of aggravation/possible expense with a project that SEEMED so relatively simple but, thanks to an overly complicated design (thanks, Jeep!), looks to not be worth the hassle. If I decide to try it out just to see if it'll work (since it's a '22 & the batteries are probably approaching replacement status soon enough), I'll let you know. You guys are the best.

Please understand, as I think you do now, that disabling the ESS system (via a button push or aftermarket tech) is an entirely independent act of taking the ESS/Aux battery out of the electrical schematic of the vehicle, the latter of which is most easily done by disconnecting the black cable at the main battery's negative terminal whose other end is not the body ground, and insulating its loose end.

For argument sake one could run the ESS system, or not, with the ESS/Aux battery connected or not.

And just because I "climbed down that rabbit hole," I'd prefer people not to run the ESS system with just the main battery because an ESS event could, in the "perfect storm," rob the main battery of enough power that by the time the vehicle realizes that this battery's voltage has dropped too low, and early terminated the ESS event, there may not be enough power in this main battery to effect an engine crank.

Of course I realize that you are opting to not run ESS events.

 

[Canucklesammich]

Yeah; I just meant that if it's too complicated/expensive to use the mini battery for the dashcam, I'd just as soon pull fuse 42 & disc the neg to eliminate electrical issues from the small battery remaining in the circuit. I'm aware that that ESS disable module simply remembers the last setting of the ESS button. That was the 1st mod I did when I got my Jeep, & still probably the best .

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