3.6L ESS Aux Battery Bypass

[William Hays]

What you describe would be a bad day. My post may have been misleading. The only cable I disconnect is the AUX Battery negative. In my career I worked with Standby Battery Systems that weighed over 3 tons. I am definitely concerned about battery fires. Have witnessed first hand what can happen with a fallen tool across the full battery stack output. Seen the handle of a 3/8 ratchet glow red and then disappear in about 1.5 seconds. Looking for a rubber end cap of proper size to slide over the end of the AUX negative lead for a added layer of protection while disconnected.

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[Jebiruph]

What you describe would be a bad day. My post may have been misleading. The only cable I disconnect is the AUX Battery negative. In my career I worked with Standby Battery Systems that weighed over 3 tons. I am definitely concerned about battery fires. Have witnessed first hand what can happen with a fallen tool across the full battery stack output. Seen the handle of a 3/8 ratchet glow red and then disappear in about 1.5 seconds. Looking for a rubber end cap of proper size to slide over the end of the AUX negative lead for a added layer of protection while disconnected.

Your post wasn't misleading, mine needs explaining. Some mechanics are not familiar with the two battery system. They will remove the negative terminal of the Main battery and assume the system is de-energized. Then they remove the Main battery positive terminal, assuming it is de-energized, and allow it to touch grounded metal. This causes a short circuit and on an unmodified system, blows a fuse. Your modification bypasses the fuses in this circumstance. With the Aux battery negative removed, it's not an issue, but if the Aux negative is reconnected, an uninformed mechanic might cause a problem. I would make sure the Aux negative cable could not be casually reinstalled. Does that make sense?

 

[Solidaxle]

If I put a battery charger on the main battery positive and negative will that be charging both batteries?
Thank you

 

[William Hays]

Your post wasn't misleading, mine needs explaining. Some mechanics are not familiar with the two battery system. They will remove the negative terminal of the Main battery and assume the system is de-energized. Then they remove the Main battery positive terminal, assuming it is de-energized, and allow it to touch grounded metal. This causes a short circuit and on an unmodified system, blows a fuse. Your modification bypasses the fuses in this circumstance. With the Aux battery negative removed, it's not an issue, but if the Aux negative is reconnected, an uninformed mechanic might cause a problem. I would make sure the Aux negative cable could not be casually reinstalled. Does that make sense?

You make an excellent point!
I am a prime example. 62 year old 3rd generation Jeep owner that has been driving them ever since I could reach the pedals. I have owned my JLR for less than three weeks. Was not aware of this electrical nightmare. Two days after purchase, I was installing my new Warn Zeon 10S winch. With my background, step one was to lift the battery cable. The day wore on, and after fighting with tightening those inside bumper bolts on the factory steel bumper, I was getting tired. Started to route the DC cables up and behind the fender liner and decided it would be easier if I cut the wheels all the way to the right. Forgetting that I had removed the battery cables, I climbed in and started the vehicle. WTF!!! Spent all night on the internet doing research and finally ending up here.
This is my first brand new Jeep and I am not use to having other people work on them. Looks like that will have to change. By the time I get the rubber end cap, electrical tape, and zip ties installed over the end of the AUX Battery negative cable, it will be clear it is disconnected for a reason.

P.S.
I still own a no rust California body and frame 85 CJ7. Attached is the build sheet.

 

[William Hays]

If I put a battery charger on the main battery positive and negative will that be charging both batteries?
Thank you

The short answer is yes, it will charge both batteries.

 

[Jeepsterfreak]

Jeep added a page to the 2019 owner’s manual that illustrated how to properly disconnect the negative terminals of both batteries. Not sure if this is applicable to the 2.0 BSG or only the 3.6.

 

[Jebiruph]

Jeep added a page to the 2019 owner’s manual that illustrated how to properly disconnect the negative terminals of both batteries. Not sure if this is applicable to the 2.0 BSG or only the 3.6.

Good find. It looks like they are making an effort to provide useful information. I don't agree with their recommendation though. I would leave the IBS connected to the battery to maintain battery history information since the IBS does not use significant power. Instead, disconnect both cables at the negative terminal.

Better yet, leave one of the batteries connected and one disconnected. If the connected battery goes dead, you should be able to start from the disconnected battery. Either battery can be disconnected with one nut, replace the regular nut with a wing nut and you have a quick and easy way put the jeep batteries in storage mode.

 

[allieboy]

Good find. It looks like they are making an effort to provide useful information. I don't agree with their recommendation though. I would leave the IBS connected to the battery to maintain battery history information since the IBS does not use significant power. Instead, disconnect both cables at the negative terminal.

Better yet, leave one of the batteries connected and one disconnected. If the connected battery goes dead, you should be able to start from the disconnected battery. Either battery can be disconnected with one nut, replace the regular nut with a wing nut and you have a quick and easy way put the jeep batteries in storage mode.

Will aux batt be charged with ground disconnected? Where can I get that jumper???

 

[Jebiruph]

The aux battery will not charge unless both the positive and negative are connected to the charger. The fuse holder and the crimp on ring connectors should be available at any auto parts store, you'll just have to attach the connectors to the fuse holder wires.

 

[Rimfire]

i am not even sure how i stumbled on to this thread but holy cow its one of the best on this entire board. fantastic information @Jebiruph ! will definitely be keeping a jumper in the dash in the event the aux battery has issues.

 

[hotttdogggg]

Both. First statement is a comment. Second statement is a question.

Wahhhhhhahahahahahahaha

 

[Jebiruph]

As an experiment, I made a batch of jumpers, but decided I didn't want to mess with the logistics of selling them. I passed that batch off to someone who is selling them here. https://www.ebay.com/itm/3-6L-ESS-A...884007?hash=item5922cbffe7:g:SKQAAOSwkR9chyYZ

 

[jhack]

As an experiment, I made a batch of jumpers, but decided I didn't want to mess with the logistics of selling them. I passed that batch of to someone who is selling them here. https://www.ebay.com/itm/3-6L-ESS-A...884007?hash=item5922cbffe7:g:SKQAAOSwkR9chyYZ

Awesome!!! Just put my order in for one. Thanks for posting this.

 

[c2m2h3]

Jebiruph, I have read the entire thread and the spin offs......VERY INFORMATIVE AND THANK YOU !

Can you go through a detailed explanation (for the non mechanically inclined) on how to fabricate your jumper.....what gauge wire has been determined to be best, the fuse size and what rated terminals ? and where do I buy this stuff from ?

Chris

 

[four low]

Jebiruph, I have read the entire thread and the spin offs......VERY INFORMATIVE AND THANK YOU !

Can you go through a detailed explanation (for the non mechanically inclined) on how to fabricate your jumper.....what gauge wire has been determined to be best, the fuse size and what rated terminals ? and where do I buy this stuff from ?

Chris

If you read all the posts, aren't "mechanically inclined", why wouldn't you simply buy a Jumper from the link above, instead of pestering the guy who has already covered this information ?

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