Jumperless Aux Battery Bypass

[Rhinebeck01]

Confused.

The fused bypass, barring no other changes to factory wiring on dual battery JLs, connects the two batteries in parallel at all times. Without the fused bypass those batteries are in parallel at nearly all times but cold cranks and ESS events(?)

But once you've disconnected the ESS negative cable that is connected to the Main battery negative terminal, in other words broken the electrical connection from the ESS battery's negative post to the Main battery's negative post, you've isolated the ESS battery. I would think then that any connection to the ESS battery's positive terminal only (a.k.a. the fused jumper connected to N1) would serve no purpose.

Aux negative is disconnected . Fused bypass jumper in use .. Aux battery is bypassed.

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[Tagoren06]

@Tagoren06

Wonder if your High Amp Fuse Array has a blown N3.... possibly blown when you did your battery swap.

I am curious about this as well, would be nice to know if it is this simple. I tried looking for other fuses that were blown maybe I just did not see this N3 fuse then. Yea I wish I could explain it, as I have read all the forums to try and fix this myself and got those results. might sound like I may not have the TSB as well, something I will have to have them take a look at.

Thank You

 

[Fudster]

Aux negative is disconnected . Fused bypass jumper in use .. Aux battery is bypassed.

Oh, I think I got it now! I was getting bogged down on the neg cable coming off Aux floating in space....

Bottom line, dual battery JL calls for electrical current on N1, which doesn't get it from Aux battery now because Aux battery is isolated, but, thanks to jumper, get its electrical current from N2, a.k.a. main battery, whose circuit is completed via main battery's negative post connection to body ground.

Thanks!!!

 

[PsychoTrucker81]

just this week I replaced the main battery and did the aux negative disconnect/F42 pull. Every time I start it, I get the Start/Stop unavailable message. This has gone on for multiple start cycles and 300 miles of driving…any ideas?

 

[Rhinebeck01]

just this week I replaced the main battery and did the aux negative disconnect/F42 pull. Every time I start it, I get the Start/Stop unavailable message. This has gone on for multiple start cycles and 300 miles of driving…any ideas?

@PsychoTrucker81

Is your N3 is blown ??

Read here..
https://www.jlwranglerforums.com/forum/threads/ess-diagnostic-help.101107/post-2094760

 

[PsychoTrucker81]

@PsychoTrucker81

Is your N3 is blown ??

Read here..
https://www.jlwranglerforums.com/forum/threads/ess-diagnostic-help.101107/post-2094760

I’ll have to check it tomorrow…everything else is working normal except for that, but I’m out of ideas lol. About ready to put an Aux battery in and be done with it if it continues doing it.

 

[Jebiruph]

just this week I replaced the main battery and did the aux negative disconnect/F42 pull. Every time I start it, I get the Start/Stop unavailable message. This has gone on for multiple start cycles and 300 miles of driving…any ideas?

There are several reasons for the Start/Stop unavailable message, is there more information available on the Start/Stop screen?

 

[PsychoTrucker81]

There are several reasons for the Start/Stop unavailable message, is there more information available on the Start/Stop screen?

There isn’t.

 

[PsychoTrucker81]

Everything on the fuse block checks out…just hooked everything back up as stock and unfortunately going to have no choice but get a aux battery to turn this stupid light off. God I miss old cars lol

 

[mdkautzman]

Everything on the fuse block checks out…just hooked everything back up as stock and unfortunately going to have no choice but get a aux battery to turn this stupid light off. God I miss old cars lol

What year was your Jeep again? I had no issues with this on my 2020 Gladiator but haven't gone down the road yet on my 2021 Wrangler. I did notice the battery negative wiring is different on a 21 to a 20 slightly.

 

[PsychoTrucker81]

What year was your Jeep again? I had no issues with this on my 2020 Gladiator but haven't gone down the road yet on my 2021 Wrangler. I did notice the battery negative wiring is different on a 21 to a 20 slightly.

It’s a 2018 Unlimited Sport 3.6.

 

[mdkautzman]

It’s a 2018 Unlimited Sport 3.6.

That's right. And you said the upgrade was completed correct.
Sorry it didn't work. This damn second battery is just something we shouldn't have to be messing with.

 

[PsychoTrucker81]

That's right. And you said the upgrade was completed correct.
Sorry it didn't work. This damn second battery is just something we shouldn't have to be messing with.

I’m not sure if the TSB was done, but from what I’ve read, if it wasn’t, once I pulled the aux ground and F42, I’d have no power, correct?

 

[Jebiruph]

Don't conflate the Stop/Start unavailable message with an actual detected failure with the ESS system. The Stop/Start unavailable message can mean the the battery sensor is reporting that the main battery is not sufficiently charged or an external factor is not conducive a Stop/Start event at this time.

If an actual failure related to the Stop/Start system is detected or there is an engine issue that would prohibit a Stop/Start event, the Stop/Start error light is turned on and the Stop/Start system is disabled.

 

[PsychoTrucker81]

Don't conflate the Stop/Start unavailable message with an actual detected failure with the ESS system. The Stop/Start unavailable message can mean the the battery sensor is reporting that the main battery is not sufficiently charged or an external factor is not conducive a Stop/Start event at this time.

If an actual failure related to the Stop/Start system is detected or there is an engine issue that would prohibit a Stop/Start event, the Stop/Start error light is turned on and the Stop/Start system is disabled.

I put it back to stock and it is back to normal. Had to replace the main battery and didn’t want to spend $125 on an aux battery for the start stop we don’t use, but is what it is. No errors for now…hopefully the aux is healthy enough that it doesn’t drain down the new battery until I get a new aux this week. I’d just deal with the light and not care, but it bothers the old lady lol.

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