Jumperless Aux Battery Bypass

[Heimkehr]

I’ve determined that my Odyssey (which turns 4 in three weeks) is ready for pasture. After a full charge + condition via my whiz-bang 20a 6 cycle Odyssey charger it quickly drops to 12.5v.

My OEM H6 battery departed this Vale of Tears at 4 years old, almost to the day. It spun the engine over just fine the evening prior, but was then dead as a doornail the next morning. The lack of any early warning was mildly annoying, but these things happen.

12.5V is an acceptable resting voltage, but that figure is also the floor. If a freshly charged battery drops very quickly to that number, as you mention, I too would consider it due for replacement.

Having used high-zoot Odyssey batteries in previous vehicles, I'd have expected the brand to provide more than a 48 month service life. It does seem the JL-generation Jeeps are just harder on batteries.

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[NeilP]

I’ve determined that my Odyssey (which turns 4 in three weeks) is ready for pasture. After a full charge + condition via my whiz-bang 20a 6 cycle Odyssey charger it quickly drops to 12.5v.

Wow, that seems like a short life for an Odyssey. I've not used one in my Jeep (yet) but I installed a pair of them in my 2000 F250 diesel in 2004. 10 years later they were still performing but I felt that it was probably time for another new set. Again, 10 years later when I sold the old girl, they were still getting the job done.

When the OEM Jeep battery dies, I will go with the Odyssey again.

 

[Deleted User 38384]

Exactly. The F42 fuse gives power to the PCR to get the signal from the computer to check the voltage on the aux battery only. By removing the fuse it just sees the main battery. Downside is you have to make sure you disable ESS or you will be starting the Jeep from a stop event with the main battery. Also remember if you have a bad aux battery it will drain off your main battery. Personal opinion I disconnected the aux negative for less of an issue to worry about.

The only part that I don't get from what Jeep chose to do with this setup, is that they chose a normal main battery and then chose to add an auxiliary battery which caused all these problems. If they just went for a larger ESS battery from the start, there would have been no need for the auxiliary battery.

I mean my wife's Subaru Forester has a ESS system and it only has one battery.

 

[AndySpill]

The only part that I don't get from what Jeep chose to do with this setup, is that they chose a normal main battery and then chose to add an auxiliary battery which caused all these problems. If they just went for a larger ESS battery from the start, there would have been no need for the auxiliary battery.

I mean my wife's Subaru Forester has a ESS system and it only has one battery.

There's less than completely confirmed reports Greg that the Aux battery proved to be an afterthought response to QA testing of an original one battery ESS solution where voltage drops during ESS events had a negative effect on the vehicle's entertainment system.

Given the location of the Aux battery I could be convinced this story true; that and reports of static on the entertainment system from owners running ESS events on factory dual AGM battery JLs with just the Aux battery bypassed, just running the main battery.

If true, why Stellantis didn't push back on their entertainment system vendor to provide a component less voltage sensitive, like just about every other vehicle running ESS with one battery stock, will remain a question for the ages.

 

[OldGuyNewJeep]

Wow, that seems like a short life for an Odyssey. I've not used one in my Jeep (yet) but I installed a pair of them in my 2000 F250 diesel in 2004. 10 years later they were still performing but I felt that it was probably time for another new set. Again, 10 years later when I sold the old girl, they were still getting the job done.

When the OEM Jeep battery dies, I will go with the Odyssey again.

I know, and I specifically paid a premium for the 94R-850 (fits in Rubicons that have tow package) thinking I’d get “extra” time with it. I also splurged for their (no longer available) Odyssey 20a 6 stage charger. I diligently charged it monthly.

Edit to add a thought I just had: I can see with my multimeter that when these things “wake up” they pull a lot of power for a minute or two. (e.g. open a door) My garage is directly below where I sit in my family room, key always in my pocket. I have proximity locks. My point being that the parasitic draw from probably near constant wake ups can’t be good for these batteries.

 

[Tyler-98-W68]

When you say "alot" of current, how much current to do you mean? Because On both my 4xe's I monitored them "waking up" and at most it was a 4.75a current for about 2 minutes and then they went back to sleep, and they did not wake up often (and this was with my keys pretty close by)

 

[OldGuyNewJeep]

When you say "alot" of current, how much current to do you mean? Because On both my 4xe's I monitored them "waking up" and at most it was a 4.75a current for about 2 minutes and then they went back to sleep, and they did not wake up often (and this was with my keys pretty close by)

Yes, same. 4-5a for almost two minutes.

 

[Gangplank]

I was getting the "Aux Switches not available" and "Start Stop Unavailable" and I think it also said "service ESS system" so I had a new Group 94/H7 battery put in this weekend.

I did the Aux Battery Bypass this weekend. Removed the smaller of the two cables from the negative terminal, taped it up and zip tied it back, and removed fuse 42. I also put the battery on my charger to ensure it is 100 fully charged.

Started it up yesterday after doing the above - the Aux Switches unavailable message went away, but it still says "Start Stop Unavailable."

Anyone have any ideas what's going on.

Picture attached

 

[andy29847]

Started it up yesterday after doing the above - the Aux Switches unavailable message went away, but it still says "Start Stop Unavailable."

Anyone have any ideas what's going on.

Picture attached

I'd use the Jeep as you would normally for a couple of days to see if the message turns off. If you still have the message, I would reset the IBS (unplug it for 15 seconds).

 

[aeonixx1001]

I'd use the Jeep as you would normally for a couple of days to see if the message turns off. If you still have the message, I would reset the IBS (unplug it for 15 seconds).

Push the ESS button as if you are disabling it. The light should stay on forever now, Unless you push the button again..The light will stay on every time you start it, dont have to push, just the first time.

 

[OldGuyNewJeep]

Push the ESS button as if you are disabling it. The light should stay on forever now, Unless you push the button again..The light will stay on every time you start it, dont have to push, just the first time.

Wut. No. Unless you have a SmartStopaStart, Tazer, or similar device you have to push that button in every cold start. SSS is the way to go, in my opinion.

As for the idiot light, that should not be on if bypass was done correctly. Try unplugging battery for 15 mins and then put back to see if it clears. Before that, make sure it’s fully charged.

 

[Ratbert]

Push the ESS button as if you are disabling it. The light should stay on forever now, Unless you push the button again..The light will stay on every time you start it, dont have to push, just the first time.

Were you trying to be funny or something?

 

[Gangplank]

I'd use the Jeep as you would normally for a couple of days to see if the message turns off. If you still have the message, I would reset the IBS (unplug it for 15 seconds).

Well ok. Wife reported back that the ESS started working again today.

All good. Now since her commute is less than 5 min. We probably need to remember to drive it at least 30 minutes on a few weekends a month or hook it up to the charger.

 

[Ratbert]

Well ok. Wife reported back that the ESS started working again today.

All good. Now since her commute is less than 5 min. We probably need to remember to drive it at least 30 minutes on a few weekends a month or hook it up to the charger.

Absolutely. Her engine doesn't fully warm up, moisture doesn't burn off, battery doesn't fully charge, more stress on her emission systems, etc. Definitely take it out to stretch its legs weekly.

 

[gxceb0t]

OK, so now my 22 JLU battery is dead. What is the recommended battery to replace it with? I'd like something that fits without modification. Then I would pull the fuse and leave the aux battery disconnected from the negative terminal and I am good?

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