Aux Battery Delete

[Mguy]

The earlier post in this thread saying it makes sense to keep / you should keep the JL's Auxiliary battery in place as an early warning system in regard to a JL/JT's batteries, was laughable at best..

..... It's not worth the time and effort to make any sense of that thought process.

On my 2018 JL, I have been running with just the Main and with the Aux battery bypassed since 2019.
I've driven over 90,000 miles with that set-up. I do believe I probably was the 1st to do the bypass on a JL. My mentor in doing this was @Jebiruph. Thanks again, Jerry!

Running with just the Main on a JL/JT is no different then running with just the Main on an old TJ or JK or any vehicle with one battery... but you @jludave know that as I do.

Reality is, running with just the Main simplifies the 12v system on a JL/JT immensely... Along with that simplification, there is thus, far less change of battery issues / less chance of getting stranded...

Unfortunately, the thought process is hard wired into the human brain. If one is good, two is better. Even with a ton of contrary evidence (human experience) constant repetition of truth doesn't seem to break through.

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[Deleted Member RoadNomad]

I am totally amazed why some on this site poopoo the Aux battery delete/fuse removal. What's even worse is they make negative comments then don't back them up with any facts or examples.

I have run my 2018 for well over a year without any issues. When I bought the jeep first thing I noticed was the start/stop was flakey plus I would get Aux switching not available also.

I immediately tested both batteries and found they were both on their way out so, I isolated the Aux battery by removing the ground cable going that connects it, removed the F42 fuse and added the Autostart/Stop bypass module. I ran it for a week or so with the ESS enabled and on the single battery just to see how it worked and it functioned normally, then I pushed the button to disable.

I have not had the first problem and no electrical gremlins.
Now if I choose to I can still use the ESS feature, I don't because it's a waste of time, saves no fuel, puts more load on the single battery and just wears out the starter.

Just because the automaker and EPA comes up with some hair brain schemes to save fuel and reduce polution doesn't mean its whats best for the vehicle or the owner. The more automakers complicate these vehicles the less reliable they become. (an the more money for the dealership) Simplify, your life will be much better!

 

[SonofaSeabee]

I am totally amazed why some on this site poopoo the Aux battery delete/fuse removal. What's even worse is they make negative comments then don't back them up with any facts or examples.

I have run my 2018 for well over a year without any issues. When I bought the jeep first thing I noticed was the start/stop was flakey plus I would get Aux switching not available also.

I immediately tested both batteries and found they were both on their way out so, I isolated the Aux battery by removing the ground cable going that connects it, removed the F42 fuse and added the Autostart/Stop bypass module. I ran it for a week or so with the ESS enabled and on the single battery just to see how it worked and it functioned normally, then I pushed the button to disable.

I have not had the first problem and no electrical gremlins.
Now if I choose to I can still use the ESS feature, I don't because it's a waste of time, saves no fuel, puts more load on the single battery and just wears out the starter.

Just because the automaker and EPA comes up with some hair brain schemes to save fuel and reduce polution doesn't mean its whats best for the vehicle or the owner. The more automakers complicate these vehicles the less reliable they become. (an the more money for the dealership) Simplify, your life will be much better!

Well said, Sir.

 

[Reinen]

Like what? Please explain how bypassing the aux battery and running with a single battery in the JL Wrangler is any different than running with a single battery in any other vehicle.

You keep talking about first sign of failure being the critical failure of the battery. This is usually NOT the case. My father was a certified master mechanic who owned a repair shop for over 50 years before he recently retired. I worked with/for him many a time. We've seen plenty of vehicles that required a new battery before the battery was completely dead and left the vehicle stranded.

My wife had a 2017 Grand Cherokee. When the battery started going, she received a warning on her dash. I don't recall exactly what the warning was/said, but she definitely had proper advance warning.

Okay....

1. Reduces cold start CCA by 20-35%. As the battery wears it will reach the point where it is unable to start the engine sooner. It's most likely to fail in severe cold which can be a very bad time to be unable to start the engine.
2. Spoofs the BCM. It's programmed for dual batteries. Yes, eTorque and 4XE have dual batteries. The Aux is the eTorque/4XE battery instead of a 2nd AGM. It's less able to avoid a critical failure due to depleted batteries.
3. Introduces the possibility that the starter will brown out and glitch the electronics during a warm start (ESS), leaving you stranded in the middle of traffic. The BCM does not account for this and help you avoid it. Again, this occurs near the end of the battery lifecycle. The JL is not a mechanical vehicle, it cannot function without cleanly powered electronics.
   1. This is greatly exasperated if higher draw electrical modifications are in use. Headlights, aux lighting, amplifiers, DC-to-DC chargers, etc. All rather common aftermarket add-ons on a Jeep.
4. The different size batteries in parallel isn't ideal but it's a much smaller issue than people make it out to be. It is better to have two batteries the same size, same manufacturer but that is only because it's more likely that they will have similar resting voltages. However the resting voltages of two new different size/manufacturer batteries won't be that far off and it only reduces battery lifespan by maybe 5% or so until they balance out. It's 100x worse to mix a new battery with an old battery, like many people with chronic battery issues have done.

So bottom line is that it significantly increases the likelihood of a critical engine start failure as the first sign of trouble and for what benefit? There really aren't any beyond not having to think about how a dual battery system works. It eliminates the small lifecycle reduction of the smaller battery but at the cost of significantly less CCA. That's more than a wash and into a negative.

Are there any other actual benefits to the Aux battery delete that I'm not seeing?

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