3.6L ESS Aux Battery Bypass

[RERAIL]

If you haven't seen it yet, I use this thread https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/ to provide the highlights of my battery related threads.

Greatly appreciate all the work that went into this thread. Built the jumper wire. Bought the Genius battery boost and printed all of the info. It now lives in the Jeep.

KS

Sponsored

 

[JPSTR]

Great info here, thank you all! My JL recently went dead sitting in my garage for a week. It would jump on main or aux battery (after removing aux battery cable from main battery and try to jump aux battery directly). I put a trickle charger on the batteries connected together, and separate, never got a green light from any connection option, but it must have taken some juice as I was finally able to jump start after several days. Took it to the dealer, they replaced the aux battery. I asked how I should connect the trickle charger as a preventative measure going forward (I don’t drive it consistently). Dealership tech said to disconnect aux battery and trickle charge aux directly, no need to trickle main battery since there is no parasitic drain if aux battery is disconnected from main and has full charge. Do you agree? How do you trickle charge your JL? Thanks!

 

[Jebiruph]

Great info here, thank you all! My JL recently went dead sitting in my garage for a week. It would jump on main or aux battery (after removing aux battery cable from main battery and try to jump aux battery directly). I put a trickle charger on the batteries connected together, and separate, never got a green light from any connection option, but it must have taken some juice as I was finally able to jump start after several days. Took it to the dealer, they replaced the aux battery. I asked how I should connect the trickle charger as a preventative measure going forward (I don’t drive it consistently). Dealership tech said to disconnect aux battery and trickle charge aux directly, no need to trickle main battery since there is no parasitic drain if aux battery is disconnected from main and has full charge. Do you agree? How do you trickle charge your JL? Thanks!

It takes awhile to charge a dead battery. I had a seldom driven pickup that always took a day to charge with a 15 amp charger when it went dead. I don't think trickle charging two dead batteries taking several days is unreasonable.

You do not need to disconnect the batteries to maintain them with a trickle charger. Unless something is malfunctioning, connecting the charger to the main battery terminals is all you need to do and has worked for several members here.

If you disconnect the aux battery, there is no need to charge it because nothing is draining it. The system electronics still connected to the main battery will drain it over time, so you would want the trickle charger connected to it. In my opinion, do to the apparent fragile nature of the aux battery, there may be some benefit to disconnecting it when stored, but you should be fine leaving it connected and charging both batteries from the main battery terminals.

 

[JPSTR]

It takes awhile to charge a dead battery. I had a seldom driven pickup that always took a day to charge with a 15 amp charger when it went dead. I don't think trickle charging two dead batteries taking several days is unreasonable.

You do not need to disconnect the batteries to maintain them with a trickle charger. Unless something is malfunctioning, connecting the charger to the main battery terminals is all you need to do and has worked for several members here.

If you disconnect the aux battery, there is no need to charge it because nothing is draining it. The system electronics still connected to the main battery will drain it over time, so you would want the trickle charger connected to it. In my opinion, do to the apparent fragile nature of the aux battery, there may be some benefit to disconnecting it when stored, but you should be fine leaving it connected and charging both batteries from the main battery terminals.

Great! Thank you for your reply and advice... great job with this thread!!!!

 

[cbrenthus]

I've seen quite a few posts related to failed Aux batteries causing flaky or dead electronics, stalling and failing to start/auto restart. I've come up with a simple way to temporarily bypass a bad Aux battery (also blown PCR fuse or bad PCR) and get back on the road. Warning - this post contains a lot of informed assumptions, so post your related experiences to help validate or invalidate any information I've provided.

Here's a picture of my bypass kit. The jumper is used to connect the N1 terminal to the N2 terminal. I wanted to be able to install the jumper securely, but still be able to quickly disconnect it. A fused jumper seemed to be the best and cheapest way to go. Removing the fuse is a simple way to disconnect the jumper and it protects against overloading the wire. I don't know how much current will pass through the wire, so I used the largest I could find.

Here's how I tested the bypass. I disconnected the Aux battery at N1 and the ground wire at the Main battery negative terminal to simulate a bad aux battery. The voltmeter confirms the disconnect with low voltage at N1.

Here's a shot of the dead instrument panel due to the disconnected Aux battery.

Here's the jumper installed between N1 and N2, voltmeter shows the Main battery voltage at N1.

Here's the live instrument panel.

Here's the instrument panel after starting, only error indicated is open hood.

For those interested, following are some diagrams to illustrate how I understand it works. (See this thread for additional information on the dual battery system https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-diagram.14401/)

Here's the battery voltages on a working system, the PCR is connecting the batteries in parallel, both batteries providing power to everything. Normal operation is verified with 0 volts between N1 and N2.

Here's the effect of a failed Aux battery, no power to critical electronics. This should be verifiable by a voltage difference between N1 and N2.

Bypassing is accomplished by jumping N1 to N2. This diagram illustrates the jumper getting power back to the critical electronics.

(updated 04/13/2019)
Additional 3.6L ESS system information is available here.
3.6L ESS Dual Battery Consolidated Information
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.2

Thank you for posting this but I tried yesterday and had a few issues and questions -

1. The nut for the terminal on N1 is captured on the wire terminal. It looks like in your picture you used a new nut - what is the spec of the nut needed?
2. From the diagrams, it looks like all you need to do is disconnect the Aux negative at the main battery negative to disconnect the Aux. If this is true, then you can install the jumper under both N1 and N2 terminals with the Aux positive connected, and don't need a new nut.
3. Just a mention - make sure the disconnect both the negative from the Aux and the negative from the main - I was getting sparks at the N1 and N2 terminals until I disconnected the aux ground (which makes sense, although my wrench wasn't touching anything else where it would ground out)

 

[Jebiruph]

Thank you for posting this but I tried yesterday and had a few issues and questions -

1. The nut for the terminal on N1 is captured on the wire terminal. It looks like in your picture you used a new nut - what is the spec of the nut needed?
2. From the diagrams, it looks like all you need to do is disconnect the Aux negative at the main battery negative to disconnect the Aux. If this is true, then you can install the jumper under both N1 and N2 terminals with the Aux positive connected, and don't need a new nut.
3. Just a mention - make sure the disconnect both the negative from the Aux and the negative from the main - I was getting sparks at the N1 and N2 terminals until I disconnected the aux ground (which makes sense, although my wrench wasn't touching anything else where it would ground out)

1. N1 nut is M6 1.0
2. I wouldn't touch the existing wiring, I would get a new nut (I prefer a wing nut) and install the jumper on top of existing cables.
3. If you are getting sparks between N1 and N2, there is a problem. N1 and N2 are electrically connected through the high capacity fuses and the PCR, unless you are auto stopped. The sparks indicate they were not connected already. If you are trouble shooting a problem, you found it. You may have a bad high capacity fuse or a bad PCR.

 

[cbrenthus]

1. N1 nut is M6 1.0

Thank you!

2. I wouldn't touch the existing wiring, I would get a new nut (I prefer a wing nut) and install the jumper on top of existing cables.

So you're saying to leave both cables connected and install the jumper? That's what I was thinking - it looks like disconnecting the aux battery negative terminal at the main battery negative is all that is needed to disconnect the aux so that it is no longer used (and then installing the jumper)

3. If you are getting sparks between N1 and N2, there is a problem. N1 and N2 are electrically connected through the high capacity fuses and the PCR, unless you are auto stopped. The sparks indicate they were not connected already. If you are trouble shooting a problem, you found it. You may have a bad high capacity fuse or a bad PCR.

No, I wasn't getting sparks between N1 and N2 - there was no voltage between them as should be the case. I just got a few sparks from a wrench solely touching the nut on those terminals. Maybe I touched something else with the wrench and grounded it, or I'm also wondering if even my body touched the jeep's body enough to allow some current to flow. But everything is normal*

*With the exception of my voltage always showing 14.0-14.2 - that is what I'm trying to troubleshoot by disconnecting the aux. I don't use ESS and I'm afraid the aux battery is starting to go bad. My new Pacifica (with the exact same engine and dual battery BS) drops to 12.x quite often.

What I really hate about this dual battery system, other than the fact that a bad aux will drain the main when the vehicle is off by being in parallel, is that a bad aux will also cause the system to constantly charge, therefore overcharging and ruining the main battery. Unless I'm missing something in the diagrams and the system is able to prevent the main from overcharging.

 

[cbrenthus]

For the last couple of weeks I'm just running with the aux batt ground disconnected from the main batt terminal and the ESS relay coil disconnected. Now that I'm happy with these results, I'm figuring out if I want to pull the aux batt completly or keep it in for a emergency jump start pack.

I like this approach - which is the relay for the ESS? Are you getting any lights on your dash?

 

[patternman]

@Jebiruph the link you inserted at the bottom of post #1 doesnt link to what the text indicates.
When i click it takes me to a thread unrelated to the consolidated info thread.

 

[Jebiruph]

@Jebiruph the link you inserted at the bottom of post #1 doesnt link to what the text indicates.
When i click it takes me to a thread unrelated to the consolidated info thread.

Thanks, fixed.

 

[c2m2h3]

I to have been following the thread. Jerry is THE MAN !!! I fully plan to buy/make a Jumper as designed above by Jerry.....I DO NOT plan to use ESS and with a Flash Cal/Pro Cal, I intend to permanently disable it.
I like the post above by cbrenthus, quoting redracer, about how to disconnect the negative and essentially disable the system. Not sure if this eliminates the Aux battery completely or not ??

Q - Does this include still using the Jumper Wire ?
Q - Can someone spell out the process with what is disconnected and what does that do for the system ?.....Also, IF you need a jump (using a portable jump pack), how do you go about that with all these wires disconnected and Jebiruph's Jumper Wire attached ?

I apologize up front if this has been covered or should be simple to figure out....I'd rather ask then make a mistake an fry the system !

 

[Jebiruph]

I to have been following the thread. Jerry is THE MAN !!! I fully plan to buy/make a Jumper as designed above by Jerry.....I DO NOT plan to use ESS and with a Flash Cal/Pro Cal, I intend to permanently disable it.
I like the post above by cbrenthus, quoting redracer, about how to disconnect the negative and essentially disable the system. Not sure if this eliminates the Aux battery completely or not ??

Q - Does this include still using the Jumper Wire ?
Q - Can someone spell out the process with what is disconnected and what does that do for the system ?.....Also, IF you need a jump (using a portable jump pack), how do you go about that with all these wires disconnected and Jebiruph's Jumper Wire attached ?

I apologize up front if this has been covered or should be simple to figure out....I'd rather ask then make a mistake an fry the system !

Can I quote you on this "Jerry is THE MAN !!!"?
If you unplug the PCR (ESS relay coil). you do not need the jumper, but you may decide using a jumper is easier. With that unplugged or the jumper installed, you can disconnect the aux battery ground and from then on it should function like a normal single battery system, including jump starting. There are lots of pics and instructions here. https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

 

[WranglerMan]

I carry the fused jumper in my glove box and have wing nuts to install I also put my JL on a Deltran Tender Plus once a month for 24-36 hrs, it’s usually a solid green in less than 18 hrs but I leave.
Normally coming off the tender my batteries are in the 13.2 range so when starting the EVIC display shows 12.7 as the alternator is not putting out that much but within 24-36 of sitting it normally shows 13.5 but if I take it on a long drive it will slowly creep down toward 12.8-13, I keep ESS bypassed all the time and doubt I will ever use it.

@Jebiruph i have a question and that would be I have looked at t(e research you have done and as curious if the ESS battery does could one just run with the jumper installed all the time with the ESS negative disconnected, this would be having ESS disabled by what ever method one chooses

 

[patternman]

If you unplug the PCR (ESS relay coil). you do not need the jumper, but you may decide using a jumper is easier. With that unplugged or the jumper installed, you can disconnect the aux battery ground and from then on it should function like a normal single battery system, including jump starting. There are lots of pics and instructions here. https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

In this configuration , does the aux battery charge?

 

[Jebiruph]

Thank you!

So you're saying to leave both cables connected and install the jumper? That's what I was thinking - it looks like disconnecting the aux battery negative terminal at the main battery negative is all that is needed to disconnect the aux so that it is no longer used (and then installing the jumper)



No, I wasn't getting sparks between N1 and N2 - there was no voltage between them as should be the case. I just got a few sparks from a wrench solely touching the nut on those terminals. Maybe I touched something else with the wrench and grounded it, or I'm also wondering if even my body touched the jeep's body enough to allow some current to flow. But everything is normal*

*With the exception of my voltage always showing 14.0-14.2 - that is what I'm trying to troubleshoot by disconnecting the aux. I don't use ESS and I'm afraid the aux battery is starting to go bad. My new Pacifica (with the exact same engine and dual battery BS) drops to 12.x quite often.

What I really hate about this dual battery system, other than the fact that a bad aux will drain the main when the vehicle is off by being in parallel, is that a bad aux will also cause the system to constantly charge, therefore overcharging and ruining the main battery. Unless I'm missing something in the diagrams and the system is able to prevent the main from overcharging.

I've not heard of the sparks before.

There appears to be nothing to prevent one bad battery from ruining the other. I was surprised myself that this was the case. One way to avoid this is with the jumper installed, you can disconnect the aux battery ground cable and leave it as an emergency backup, reconnecting when needed.

As far as your voltage, mine has always run high since I started monitoring it over a year ago. I checked today and it was 14.6V. I think it's the short trips and the system over compensates. If your concerned about the aux battery, a quick and simple load test is to use it to start with the main battery disconnected.

Sponsored