JL JUMPSTART

OP
OP
allieboy

allieboy

Banned
Banned
First Name
Bob
Joined
Jan 17, 2019
Messages
218
Reaction score
184
Location
Phoenix
Vehicle(s)
2019 Sahara
It will theoretically work, the variables are how much power is in the powerbank and how drained is the main battery.
Can a jumper like yours be purchased? If not...what materials like guage of wire do you use? You are a ROCK STAR!
Advertisement

 

Majestic

Well-Known Member
Joined
Dec 27, 2017
Messages
659
Reaction score
626
Location
NC
Vehicle(s)
2013 JKUR, 2019 JLUR
@Rahneld

The link in your post takes you to a post I made in July 2018. Can tell you that since then, I and other's here, have learned so much more about the Main and Aux batteries and how they play together lets say.

As for me, I think at this point in time / now .... I have a pretty good or at least a much better understanding of the aforementioned. I know I am lets say up to speed on jump starting the JL and more.

I encourage you and other's interested in learning more on this talking point, to do a forum search in regard to all posts made by forum member @Jebiruph . You read all of the posts he has made over the last say 6 months..... and you will have a better understanding to say the least of the two batteries in a 3.6L JL. @Jebiruph has posted pics, diagrams, explanations and more.... much more. DO take the time to to do lots of research.

@Jebiruph, also provided me with / sent me, one of his jumpers, which I have been testing with over the last few months. I know @WranglerMan was also sent a jumper and he too has been testing.

In closing, there is so much I have learned and I'm still learning more each day. There are so many unknowns with this battery(s) thing.

I know I am better prepared now then I was when I had my battery depletion and no start situation. For sure I am much better prepared now then I was.

.
I think what’s sad here is that there is so much to learn and there really shouldn’t be. Car batteries have worked the same way for almost 100 years and suddenly we need to reverse engineer the ignition system just to teach ourselves how to jump start a dead battery.
 

Rahneld

Banned
Banned
First Name
Ronald
Joined
Jan 26, 2019
Messages
1,114
Reaction score
671
Location
Boston
Vehicle(s)
JL Wrangler
@Majestic I appreciate your sentiments.

I especially (and others) don't have complete understanding of how this system works.

There may, for example, be solid reasons why FCA *seemed* to design the system to be dependent upon a battery (ESS) that operates an optional system (ESS) (discussed below.) I agree with what I think is your premise that maybe FCA should be more open about what exactly is happening here, when, and why.

I'm sure time will reveal this, just as people really in the know here relative to others, like @Jebiruph and @Rhinebeck01, know more today than 6 months ago.

Instead, FCA *seems* to be not only avoiding, but skirting around the fact that the JL's "jump start" may really be a "quickie minimal charge first, then jump start," because of how the JLs batteries and electronics were devised, with owner's manual speak like :

"Start the engine in the vehicle that has the booster battery, let the engine idle a few minutes, and then start the engine in the vehicle with the discharged battery."

Let the (booster) engine idle. Hmm...ok, maybe if the booster vehicle was itself just cranked...to have its alternator replenish energy lost from the battery during the crank......but does this logic also apply to a tow truck with heavy duty power whose engine (and alternator) has been on since 4AM (and I think "yes")?

Maybe the following language is more honest/accurate. Again I am not certain:

let the JLs batteries charge for a few minutes
.

====

To my understanding, (maybe wrong) the device that signals the starter (the starter relay) is, at the time this relay's invoked, solely dependent on the ESS battery having juice, (as the 2 batteries are isolated during such an event)...even if the starter works directly off the main battery at that battery isolation point as well. (Specialists: flame this, with apologies, if wrong.)

That the 2 batteries are normally connected in parallel at other times is only as good as the ESS battery can accept a charge, be it mostly from the alternator during engine run, or the main battery when parked: even possibly depleting the main battery (when parked) in its in vain attempt to rescue an ESS battery that has permanently failed---wasting rather than accepting main battery power, and in need of replacement.

Like @Jebiruph said, the ESS battery seems like "Gilligan:" well intentioned but at times inept (reference to 60's TV Show Gilligan's Island.)

My ignorance is boundless here, and yet a part of me wishes (I think?) the system, upon cold crank and determination of ESS battery failure, to fall back on the main battery: which @Jebiruph's N2<->N1 jumper, or the pricey dual battery kit seems to do. In fairness, my ignorance may prevent me from accurately reporting here, or even if understanding the principles at play, fail to make me appreciate why this wasn't built into the design.

I get the dual battery kit for those who fill their JLs with power intensive equipment and/or offroad: pulling juice when the alternator isn't putting it back. It appears as pricey as well designed.

....but for me: not as a means to simply make a daily driver more fault tolerant.

~~~~~~~~~
 

Rahneld

Banned
Banned
First Name
Ronald
Joined
Jan 26, 2019
Messages
1,114
Reaction score
671
Location
Boston
Vehicle(s)
JL Wrangler
To bring this thread full circle back to the OP's initial question, which interests me too, might the JL (at least the 3.6L engine one) have its engine cold cranked by two power packs?

...one to charge the batteries to a minimal level, and a second, maybe more deep cycle in design, to aid with the cranking of the engine?

: - )

It seems the stuff jokes are made of. How many battery packs (X group of people) does it take to crank a 3.6L JL (screw in a light bulb?)
 

Rahneld

Banned
Banned
First Name
Ronald
Joined
Jan 26, 2019
Messages
1,114
Reaction score
671
Location
Boston
Vehicle(s)
JL Wrangler
Parting thoughts for now.

It seems to me (I may be wrong) that the ESS battery should have been designed to solely operate the optional ESS system and nothing else (like the mission critical starter relay it seems to power in isolation at crank.)

Further, I would have liked to see a factory setup where if, while parked, the main battery was getting depleted below a threshold of power by the ESS battery's needs (say a defective ESS battery that won't accept, but won't stop taking a charge from the main battery) that the main battery cuts off power to the ESS battery.

And that engine crank and vehicle function (and jump starting) not be compromised by ESS battery problems, @Jebiruph's N1<->N2 jumper workaround or a dual battery system notwithstanding.

Worst case, to my mind should have been that if the ESS battery is dead/faulty, that ESS doesn't engage at vehicle stops and diagnostics reveal this, not that the 3.6L doesn't cold crank.

I don't know all there is to know about this system, or as much as specialists on the board in this, but would you design an aircraft to not be flight worthy simply if one of the bathroom toilets became clogged?
 

bobUK

Member
First Name
Rob
Joined
Mar 18, 2019
Messages
10
Reaction score
2
Location
UK
Vehicle(s)
Merc
I Came across this thread and thought this may help, my car is a Merc so could be different from Wrangler. On the Merc the small aux battery is for stop/start only, everything else is driven by the main starter battery, I believe your battery problems are caused by the computer controlled smart alternator which looks at the SOC of the battery via a sensor attached to the negative rail of the main starter battery under the Hood. If the ECU sees the main battery is low ( may not crank the engine ) stop start will not be engaged. The ECU will not allow the main battery to be charged beyond 80% by the engine, the other 20% can only be filled by regeneration, if there is little regen on the journey the main starter battery will remain near to 80% full which is not too far off flat.

To test this buy this from Ebay ( https://www.ebay.co.uk/itm/Vehicle-...r-Checker-2-8-1-6-1-2inch-Black/223104900451? ), test the charge rate with sensor connected then disconnect sensor drive car for a few days and see if the battery problems have been resolved, if they have this proves it`s the smart charge system which can only be resolved by plenty of regen or disconnection, if disconnected you loose stop/start but will always have a fully charged battery, regards.
 

NathanG

Well-Known Member
First Name
Nathan
Joined
May 25, 2018
Messages
285
Reaction score
327
Location
Tucson AZ
Vehicle(s)
2018 JLU Rubicon
Vehicle Showcase
1
If you have an issue with your aux battery ( a fragile weak POS that fails if it is overtaxed by accessory loads with the car off) no amount of trickle charging will bring it back. If your main battery is dead than a normal jump might work. If you have a charged main battery and a faulty aux battery you can use a battery boost connected to ground and terminal N1 under the fuse cover.

I fried my aux battery somehow using a ARB compressor for a few moments with the ignition off powered by the aux switches and trying to start the car with it running. After that it wouldn't restart. Trickle charging both batteries together or separately didn't work. Only the booster worked on N1.

There could also be a fried fuse block causing problems. Or the intelligent battery sensor system.

Even after all this I am not complaining. It is a new system we will just have to learn and figure it out, like electronic ignition vs points. Or fuel injection vs carbs. Its part of the adventure!
 

Jebiruph

Well-Known Member
First Name
Jerry
Joined
Feb 18, 2018
Messages
1,450
Reaction score
1,802
Location
Iowa
Vehicle(s)
2018 JLU, 2019 KL, 2020 JT
I Came across this thread and thought this may help, my car is a Merc so could be different from Wrangler. On the Merc the small aux battery is for stop/start only, everything else is driven by the main starter battery, I believe your battery problems are caused by the computer controlled smart alternator which looks at the SOC of the battery via a sensor attached to the negative rail of the main starter battery under the Hood. If the ECU sees the main battery is low ( may not crank the engine ) stop start will not be engaged. The ECU will not allow the main battery to be charged beyond 80% by the engine, the other 20% can only be filled by regeneration, if there is little regen on the journey the main starter battery will remain near to 80% full which is not too far off flat.

To test this buy this from Ebay ( https://www.ebay.co.uk/itm/Vehicle-...r-Checker-2-8-1-6-1-2inch-Black/223104900451? ), test the charge rate with sensor connected then disconnect sensor drive car for a few days and see if the battery problems have been resolved, if they have this proves it`s the smart charge system which can only be resolved by plenty of regen or disconnection, if disconnected you loose stop/start but will always have a fully charged battery, regards.
No regeneration on the 3.6L ESS.
 

Onyx Dragon

Well-Known Member
Joined
Mar 11, 2019
Messages
269
Reaction score
248
Location
Virginia
Vehicle(s)
2018 JLU, 1999 Xj, 2001 Trans Am
Vehicle Showcase
3
@allieboy

Why should I search for YOU ? Takes seconds for you, the OP, to search for yourself.
Because if you have the answer, or can provide it, you should. Otherwise, why bother posting? Open the thread, start to read, see what it's about, and then leave. Otherwise it's just a useless post.
 

American Adventurist

Well-Known Member
First Name
Dave
Joined
Jun 16, 2018
Messages
559
Reaction score
515
Location
West Florida
Vehicle(s)
2018 StingGray JLUR
I think what’s sad here is that there is so much to learn and there really shouldn’t be. Car batteries have worked the same way for almost 100 years and suddenly we need to reverse engineer the ignition system just to teach ourselves how to jump start a dead battery.
Amen.
 

midwestmaob

New Member
Joined
Sep 14, 2019
Messages
3
Reaction score
0
Location
Chicago
Vehicle(s)
2019 Moab
Not here to stir the pot or start a debate, just report my experience jumping my JL that I accidentally drained to shit over a few days, (long story by drove myself to a surgery and must have left it in drive, allowing ess to run both batteries down.

At this point I didn’t think to open the manual, just tried jumping my using a portable jump battery from Costco, that I’ve used successfully on many other cars with no problem. No such luck, the portable drained to nothing before enough juice to start. Figuring my portable was shot and me running hot, I waited for the security guys at the hospital to jump with their much more substantial portable pack and still no dice.
Got home, read this forum and then went back the next day with another vehicle and it finally started after a 40 minute wait (tried at 20 and nothing)..Christmas tree of lights on dash but no cranking.

Just posting this because I figured after 20 minutes of jumping before trying to start, that I figured something else was wrong with the Jeep. At 40 -45 it finally turned over.

After it did start, I had an engine light for about 24 hours, that finally went out. I assume low voltage and then adjusted. Realized after the fact that I could have checked from dash info.—Again smart af, but not as brilliant as the design IMO.

Only intent here is to help the someone in the middle of a wtf when 2019 Jeep JL won’t jump start.
 

Rahneld

Banned
Banned
First Name
Ronald
Joined
Jan 26, 2019
Messages
1,114
Reaction score
671
Location
Boston
Vehicle(s)
JL Wrangler
Not here to stir the pot or start a debate, just report my experience jumping my JL that I accidentally drained to shit over a few days, (long story by drove myself to a surgery and must have left it in drive, allowing ess to run both batteries down....
@midwestmaob I'm sorry not only for your bad automotive results but the surgery that may have taken your mind off the rig while you drove yourself to the appointment.

I hope both you and your rig are okay.

A while back I wrote a long article on what I felt were the likely reasons that a jumpstart from a booster usually fails or takes too long on a 3.6L JL and what to do about it.

I'll try to rehash but keep things short[er].

My friend, if you have a 3.6L JL, that jump start event you are trying, by connecting your booster to the terminals of the main battery is really a wasted attempt to charge the ESS battery enough to allow the rig to crank, all while also charging the main battery--dead though it may be--an unneccessary step to get going that steals power from the booster to also charge the main battery, which need not have charge to get going.

You see when the rig isn't on, both batteries are connected in parallel so connecting to either battery's terminals is a connection effectively to both batteries terminals.

Before the 3.6L JL will attempt a crank, the ESS battery must, all on its own, have a basic charge--and interesting enough, you don't even have to have the main battery connected to crank the rig provided the ESS battery is charged. This has already been tested, and interestingly enough, the converse (the main battery only) won't work. I won't get into why except to say it was designed that way for a reason I don't approve of.

Here's what you need to do to **possibly** get the booster to not only work, but fast.

  • Connect the positive of the booster to terminal N1 on the high amp fuses in the PDC. The PDC is the power distribution center, located close to the fire wall on the passenger's side under the hood. Take its cover off on on the driver's side of the unit, in a row, from front to back is a series of terminals, N1 being closest to you the front of the vehcile . And BTW, touch only N1 (don't touch N2). N1 leads directly to the ESS positive terminal. This is simply easier than digging out the ESS battery to get to its positive terminal: the ultimate goal.
  • Connect the negative of the booster to the negative terminals that lead to the main battery's negative post, only having first disconnected those negative wires temporarily from the main battery's negative post first.

What you've done here is make the ESS battery and your booster as one, connected in parallel, as well as take the main battery out of the picture.

Hopefully this tricks the rig into thinking the ESS battery has juice, or at least it dedicates all the booster's charge to charging the ESS battery.

Try cranking ASAP. If it works you can connect back the leads to the main (be careful!) battery and disconnect the booster. The alternator will take over from here. You can ride around to charge your rig, or at least take it someplace (your service center/home) with gear to properly charge things back up.

I hope this helps. If you have questions on the hows and why of this hit my back with a reply. : - ) I realize it involves keep some (metric) tools on your rig.

Cheers.
 
Last edited:

Rahneld

Banned
Banned
First Name
Ronald
Joined
Jan 26, 2019
Messages
1,114
Reaction score
671
Location
Boston
Vehicle(s)
JL Wrangler
I don't want to leave people with the impression that the main battery isn't used in (cold or ESS) starting the rig--it is if connected and in possession of ample power--it just need not be used.

(In fact the ESS system is designed to preserve the main battery during ESS events just for this purpose...BUT)

The best research of the forum suggests that after the 3.6L checks that the ESS battery, all on its own. has adequate power prior to crank, (and that the crank won't be attempted by the rig if it doesn't,) that the ESS and main batteries are then reconnected in parallel prior to, and to effect the crank, where, if present, (it need not be) the main battery will presumptively (because its bigger) bear the larger responsibility for powering the cranking motor to crank the engine.

(In the 3.6L the two batteries are always in parallel but for ESS events and when prior to a cold crank, the ESS battery is tested in isolation for adequate power.)

But the ESS battery, fully charged, is capable of doing this crank on its own, and with the alternator, after a successful crank, being able to power the 3.6L with no main battery connected.

In cases of two dead (but capable of being charged) batteries, we want to allocate our booster's limited power most efficiently (i.e. directly at the ESS battery in isolation) to get going, and allow the alternator to take over the power needs and the dual battery recharging needs of the rig after a successful crank, to charge both batteries, or at least get you to a location less isolated (home/service center) to have a more substantial power source, over a longer period of time, sit on the main battery's terminals, with the battery wires connected as per factory setup, to charge both batteries.

The above 't technique doesn't guarantee successful crank with a booster. That's a product of the booster's rating, and the presumption that the rig is dead because the ESS battery is dead, but capable of taking charge. What it does is increase the odds of a successful crank, in, by the way, a faster period of time than waiting for the standard jump start from, say, a tow truck, to sit on the main batteries terminals and charge both batteries.

I see no reason why the tow truck jump start can't also connect to N1 and the floating in mid air negative cables of the main battery (as per the prior post) to get going faster, albeit at the expense of the alternator charging the batteries of a cranked 3.6L rather than the jump start waiting period effecting same.

Cheers.
 
Last edited:
Advertisement

Superchips TrailDash 3
 
Advertisement
Top