Auxiliary battery bypass.

[Doctor Wu]

Hello. I am a newbie here and have a question that I could research or just ask. I have bypassed my aux battery on my 22 JL by disconnecting the negative cable and pulling fuse 42. Did this as I had the start stop warning light (start stop wasn't working)and I was having to get jumped all the time. Recently replaced the main battery but the start stop function is still working. How can that be with the battery and fuse disconnected? Is this draining my main battery somehow? Driving for 3 days now so the computer should be aware also. Thanks for any insight. I know this question has probably been asked one way or another many times here.

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[andrei]

I saw @AndySpill delivering some solid asskicking on bypass in another thread, maybe he can help?

On a side note, i recommend investing into a plugin ESS disabler. Been rocking one in mine for over a year, forgot that retarded ESS even a thing, still need to do aux disconnect.

 

[andy29847]

Hello. I am a newbie here and have a question that I could research or just ask. I have bypassed my aux battery on my 22 JL by disconnecting the negative cable and pulling fuse 42. Did this as I had the start stop warning light (start stop wasn't working)and I was having to get jumped all the time. Recently replaced the main battery but the start stop function is still working. How can that be with the battery and fuse disconnected? Is this draining my main battery somehow? Driving for 3 days now so the computer should be aware also. Thanks for any insight. I know this question has probably been asked one way or another many times here.

The stop:start system is not dependent on the aux battery. If still works with just the main as long as the battery is good.

 

[Doctor Wu]

So then the purpose of doing what I did is too just eliminate the need to replace the auxiliary ever again? The YouTube videos on this all imply it fixes the problem....?

 

[andrei]

So then the purpose of doing what I did is too just eliminate the need to replace the auxiliary ever again? The YouTube videos on this all imply it fixes the problem....?

I think its more like protection against consequences associated with aux draining. From what i have seen, JL will go retard and leave you stranded when aux goes bad.

 

[Doctor Wu]

I guess I will be hitting the disable switch each time then. Or buy the thing that disables it. I am not really seeing the point of the auxiliary battery if it all works without it.

 

[X35]

Pulling fuse 42 and disconnecting the AUX battery cable from the main battery negative simply eliminates it (the AUX battery) from the Jeep’s electrical system. It will not disable the start stop bullshit

 

[AndySpill]

Hello. I am a newbie here and have a question that I could research or just ask. I have bypassed my aux battery on my 22 JL by disconnecting the negative cable and pulling fuse 42. Did this as I had the start stop warning light (start stop wasn't working)and I was having to get jumped all the time. Recently replaced the main battery but the start stop function is still working. How can that be with the battery and fuse disconnected? Is this draining my main battery somehow? Driving for 3 days now so the computer should be aware also. Thanks for any insight. I know this question has probably been asked one way or another many times here.

I'll answer @andrei, and do so nicely. My more terse prior response was to someone out to be IMHO pedantic for pedantic sake. @Doctor Wu Al simple seeks to understand; I'm glad to help.

Al: lets understand the process. When we do, all questions will be answered.

And let's start with a factory untouched dual AGM battery JL: i.e. your vehicle when you got it.

When you press that brake and push the start button your vehicle energizes the PCR or Power Control Relay for an instant prior to attempting an engine crank. This is a device that temporarily disconnects the two batteries when energized. It does so to allow the batteries to each be tested independently of one another. After this near instantaneous occurrence, power to the PCR is withdrawn, the batteries are reconnected, and both power the engine crank. The only other time the PCR is energized (separating the batteries) is during engine start stop events (ESS).

I'll bet that a weak Aux battery was detected during this process I just described and caused the start stop warning light you saw.

Now...you effected the battery bypass. When you did you broke the circuit to the Aux battery. It now neither powers any vehicle appliance nor receives alternator power. It sits electrical isolated. Additionally you pulled Fuse 42. This circuit powers the Power Control Relay.

Now, lets talk about your engine crank process with these changes. When you start the vehicle it attempts to energize circuit 42 to open the Power Control Relay. It can't; you pulled its fuse (by design). And the vehicle doesn't complain (in the dash) about that.

Now, that pre-crank test of the batteries goes to all connected batteries (because the PCR, deprived of power, can't separate them,) of which you have but one: your main battery. Your vehicle thinks its tested the batteries: it truth it only tested the main battery, wrongly thinking it was the Aux, and then the main battery, correctly thinking it was the main battery.

Your vehicle was very happy with the power it saw on your "Aux" battery, a.k.a. your new main battery and allowed the start stop function to work again.

The irony here is that despite the vehicle now thinking all is fine and dandy about running ESS events with such a well powered Aux battery (a.k.a. in truth your main battery), I recommend you turn ESS off at the dash or buy aftermarket tech to do so with running with this bypass.

The vehicle was designed to run ESS using the Aux battery to help the post ESS event engine crank: that ESS event depleting battery power while the engine was off and no alternator was backfilling batteries with power.

For a long time we thought appliances were run off the Aux battery during ESS events. Last November some tech gurus revised that https://www.jeepgladiatorforum.com/...eries-really-isolated-during-ess-stops.87524/ but still concluded ESS events best run on the dual AGM battery JL or JT with 2 batteries.

I hope that helps.

 

[X35]

I guess I will be hitting the disable switch each time then. Or buy the thing that disables it. I am not really seeing the point of the auxiliary battery if it all works without it.

My recommendation :

https://www.smartstopstart.com/jeep-dodge-chrysler-products.html

 

[Doctor Wu]

What are all the misleading videos on YouTube then saying it works? Very confusing to a common man such as myself.

 

[X35]

What are all the misleading videos on YouTube then saying it works? Very confusing to a common man such as myself.

Well, you can’t trust YouTube or any other AI bullshit

 

[THAW]

So then the purpose of doing what I did is too just eliminate the need to replace the auxiliary ever again?

Yes, precisely.

 

[4x4 Mule]

I have had a plug in ess disabler on both my ‘22 Grand Cherokee and ‘24 Ram 1500 since new - no issues yet with auxiliary battery’s … I also plan on putting one on my ‘41 Willys as soon as it arrives

 

[andrei]

My recommendation :

https://www.smartstopstart.com/jeep-dodge-chrysler-products.html

Amazon sells cheaper variants

 

[X35]

Amazon sells cheaper variants

Obviously, however, a man should always purchase the best that he can afford. I’ve had no issues with mine and it looks stock among the other wires and modules under the steering column

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