Aux Battery By-Pass

[SonofaSeabee]

Hello forum, I read through the 45 page thread in regards to Aux battery by-pass, lots of info. Figured I would just post my own thread, not clog up previous thread, to get a quick answer. I am going to do the by-pass sometime today, just need reassurement from others that I am following the procedure from those that have done it. I already have the SmartStopStart in the Jeep to automatically press the button to turn off stop/start. Attached is two photos, with yellow arrows, of the two things to remove. Am I correct with disconnecting, which looks to me, to be the smaller gauge negative cable, at the main battery, which would be the aux battery negative cable, and taping the end of that up and tucking away? Second, pulling the red 10A fuse with yellow arrow pointing to it?
I have read that the best procedure order is:
1. Pull fuse first
2. Disconnect/tape/tuck away aux battery negative second
Thoughts from forum? Thanks!

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[jludave]

Am I correct with disconnecting, which looks to me, to be the smaller gauge negative cable, at the main battery, which would be the aux battery negative cable, and taping the end of that up and tucking away?

It should be the thinner/smaller of the 2 cables.

Second, pulling the red 10A fuse with yellow arrow pointing to it?

You want to pull fuse F42. Look at the inside of the fuse box cover. That should show where that fuse is. Off the top of my head, your arrow appears to be pointing to the correct fuse.

I have read that the best procedure order is:
1. Pull fuse first
2. Disconnect/tape/tuck away aux battery negative second
Thoughts from forum?

Correct.

 

[SonofaSeabee]

By the looks of my photo, it looks like both negative cables need removed, in order to get the aux negative off, because aux negative is under main negative due to wider blade? Do I reconnect the main negative where it was taken off from, or move over to where aux negative was? Does the aux negative wide blade create some sort of bridge from main negative to aux negative?

 

[jludave]

By the looks of my photo, it looks like both negative cables need removed, in order to get the aux negative off, because aux negative is under main negative due to wider blade?

You will need to test which is actually the AUX negative. Some have found in later model years, that the aux cable was not the thinner/skinnier of the 2. Go back and look through the full Jumper less AUX Bypass thread - https://www.jlwranglerforums.com/forum/threads/jumperless-aux-battery-bypass.95945/

Do I reconnect the main negative where it was taken off from, or move over to where aux negative was?

Put the main back where it was.

Does the aux negative wide blade create some sort of bridge from main negative to aux negative?

Yes. Under normal conditions, without the bypass, both batteries are connected.

 

[jludave]

@SonofaSeabee

Look here:

https://www.jlwranglerforums.com/forum/threads/ess-battery-cable-change.86624/

 

[SonofaSeabee]

By-Pass done. 20 minute test drive showed no ill effects, no warnings or messages. Should be good to go. Literally 5 mins job.

 

[dchemphill1]

It appears you have the correct items labeled. So pull and disconnect. BTW this just takes the AUX out of play. The ESS will still function with the main battery if you don't push the button on the dash everytime or use jscan or another device to stop the function.

 

[AndySpill]

I hold the opinion that you should turn ESS off. Whether you do it each time with a button push or you acquire aftermarket tech to do it automatically for you makes no difference here.

If you forget to turn ESS off it isn't the end of the world. Essentially you'll be running ESS like every other vehicle out that there has it: with one battery.

But your JL was designed for it to work with two batteries, sparing the main battery to effect the bulk of the cranking load (both batteries, if present, energize the crank) or entire load of the crank if you've yanked the ESS battery, and the perfect storm of a cold night, an old main battery, a long traffic light, and too many energy hungry appliances running during an ESS event may rob the main battery of adequate power to crank the engine before the vehicle early terminates the ESS event due to low voltage in what it thinks, none the wiser, is the ESS battery, but is actually, thanks to the Fuse 42 pull, your main battery.

Pulling fuse 42 first is neither wrong nor required. The only time current runs through that circuit, which when it does opens a normally closed relay: the Power Control Relay (PCR) that separates the batteries is during an instant prior to cold crank and during ESS events. With your engine off, whether you yank the battery cable or fuse first is of no consequence as long as both are effected prior to your next cold crank.

 

[DaltonGang]

@SonofaSeabee . Don't listen To those scared to take a leap of faith, and do what many others have done. You did the right thing. Welcome to gaining back some reliability.

 

[Whiskeybiskit]

Did this, this past Friday. Second time changing the main battery because of the aux battery, which I feel is the only reason the main battery dies sooner than it should. Disconnected the negative cable and pulled fuse 42, no issues since then. I have had the smart startstop bypass for a few years now too, my ess is never on. Not paying for two batteries again.

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