ESS Battery Cable Change

[lakebuster]

OK the larger cable going to negative post once removed was reading 2V from Fluke, tested smaller cable and it read 13V, connected to negative terminal still showed 13V and no power past battery into Jeep. No lights, No start, Nothing.
Can someone help me out please!

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[BDinTX]

Hi David,
Try disconnecting both your main battery and aux battery grounds so you have no power and test the fuses in your high current fuse array. You might have popped one of those attempting to eliminate the Aux battery.

Copied from an earlier post of @Jebiruph

Also, put a couple of pics in of what and how you're measuring 2v.
I didn't realize we had something under the hood that would beep like that. Did you add anything aftermarket?

 

[lakebuster]

Hi David,
Try disconnecting both your main battery and aux battery grounds so you have no power and test the fuses in your high current fuse array. You might have popped one of those attempting to eliminate the Aux battery.

Copied from an earlier post of @Jebiruph

Also, put a couple of pics in of what and how you're measuring 2v.
I didn't realize we had something under the hood that would beep like that. Did you add anything aftermarket?

OK thanks will do!

 

[BDinTX]

Also focus your troubleshooting efforts in one thread please

 

[lakebuster]

Hi David,
Try disconnecting both your main battery and aux battery grounds so you have no power and test the fuses in your high current fuse array. You might have popped one of those attempting to eliminate the Aux battery.

Copied from an earlier post of @Jebiruph

Also, put a couple of pics in of what and how you're measuring 2v.
I didn't realize we had something under the hood that would beep like that. Did you add anything aftermarket?

Only aftermarket items is a AF1 braking system and a charger while being pulled by MH. Both of there fuses are pulled
Connecting to Fluke on large ground now shows 0 volts, connecting to small ground shows 13V

 

[Fudster]

Only aftermarket items is a AF1 braking system and a charger while being pulled by MH. Both of there fuses are pulled
Connecting to Fluke on large ground now shows 0 volts, connecting to small ground shows 13V

Hi David:

I think I know from the Jumperless Bypass thread that your goal is to remove the ESS battery from your JLs electrical schema. If that's not your goal please correct me.

That said, you have taken your meter and put one end on the positive terminal of the main battery (which is connected to the positive terminal of the ESS battery).

Then, the other end of your meter got connected in one picture to the cable who's distal end is connected to the negative terminal of the ESS battery, and your meter read that battery's voltage.

Then you moved the negative side of your meter to the cable whose other end is connected to the body ground and good some residual voltage.

Ok. This is kind of what I'd expect.

The black cable you got the voltage on. Wrap that cable end up and isolate it. Then, the other cable, which connects at its distal end to the body ground, reconnect that to the negative terminal of the main battery.

These two actions, along with pulling Fuse 42 should take the ESS battery out of the electrical schema of the vehicle, restore the main battery into the electrical schema of the vehicle, and prevent the relay that can separate the two batteries (much as you now only have one battery) from ever being separated.

When you do this you still have no good luck?

 

[lakebuster]

Well I found the problem, even though large ground cable read zero connecting meter to positive it read 13 V when I connected it to the battery sitting on top of the IBS. Now to clean up wiring and it is a wrap.
Thanks for everyone’s help!

 

[lakebuster]

Also the beeping noise, today it happened again. Thought something was wrong and found it.
It is the CO detector it is doing its Job!

 

[TeamToad]

Just to clarify, you're referring to the terminal styles, right? The thinner cable, regardless of the terminal used, still goes to the aux?

The easy way to be sure is to measure Ohms between each cable and the body.

After you've disconnected both ground cables, the main cable will have 0 Ohms, and the aux cable will have infinity (open circuit).

On my 2023 JLURD the aux cable has a large yellow and black warning label on it.

 

[Canucklesammich]

The easy way to be sure is to measure Ohms between each cable and the body.

After you've disconnected both ground cables, the main cable will have 0 Ohms, and the aux cable will have infinity (open circuit).

On my 2023 JLURD the aux cable has a large yellow and black warning label on it.

Cool, thx for the info. I was apprehensive about disconnecting both, didn't know if this would reset the radio, etc; but ya gotta do what ya gotta do.

 

[OBD]

At some point (MY21?) a change was made to the ESS negative battery cables, swapping the cable ends between the aux battery cable and the body ground cable. This makes it easier to disconnect both batteries from body ground, but makes it more difficult to disconnect just the aux battery.

Here's the main battery negative terminal with the battery sensor attached and the cables disconnected.
Cable A old connects to the body ground, new connects to the aux battery negative.
Cable B old connects to the aux battery negative, new connects to the body ground.

With the old cables, disconnecting cable B disconnects just the aux battery negative. With the new cables, this should disconnect both batteries from the body ground.

With the new cables, removing both cables and reconnecting cable B (body ground) should disconnect just the aux battery.

Here is my 21 with what I believe is the new cable set up.Thanks for this post.I have been confused as hell.I couldn't understand why the large ground cable was supposedly going to the small battery.

 

[OBD]

Here is my 21 with what I believe is the new cable set up.Thanks for this post.I have been confused as hell.I couldn't understand why the large ground cable was supposedly going to the small battery.

Here is my modified adapter.I drilled and tapped a hole in the top for a larger bolt for the larger ground cable.The adapter is deep enough, but I did tap it with fine threads.

 

[BDinTX]

Here is my modified adapter.I drilled and tapped a hole in the top for a larger bolt for the larger ground cable.The adapter is deep enough, but I did tap it with fine threads.

Nicely done!
Using your post as inspiration I just did similar.

If anyone that wants to try it you’ll need these:
https://www.amazon.com/dp/B09V59NX9C?psc=1&smid=A1OUHRIC0G8FCS&ref_=chk_typ_quicklook_imgToDp

This is how I did it:
1) in a vise and cut the male end off with a hacksaw.
2) file the remaining nearly flat (doesn’t need to be perfect)
3) place the remaining nub in a washer and drill through the FEMALE side with a 5/64 bit. It should self center but try to be accurate.
4) flip it female side down, drill out the hole you just made with 7/64 then 9/64 bits.
5) run an M6x1.0 tap through from the female side

I cut a bolt down that I had, you have 3/8” of threaded hole to use. After the washer I needed 14mm of bolt.

 

[Go Hogs!]

Here is my modified adapter.I drilled and tapped a hole in the top for a larger bolt for the larger ground cable.The adapter is deep enough, but I did tap it with fine threads.

Is it necessary to make an adapter for this connection? I have seen several that put the connector on without any modification despite the size difference.

 

[BDinTX]

Is it necessary to make an adapter for this connection? I have seen several that put the connector on without any modification despite the size difference.

Take a look at the first post in this thread. Some time in 2021 they changed the two ground cables, that is what requires these adapters.

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