Why 3.6L Jumpstarts are the way that they are

  1. Rahneld

    Rahneld Well-Known Member

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    #1 Apr 16, 2019
    Last edited: Apr 26, 2019
    4/26/19 Since writing this thread, @Jebiruph has done some testing that suggests the changes below, written in this color.


    Plenty of excellent threads have been written about how to jumpstart the 3.6L JL. How things get hooked up, in terms of what cables to place where, and in what order are no different than jump starting pretty much any other ICE (internal combustion engine) vehicle. Even allowing the booster vehicle to run a few minutes is the same. But what is going on behind the scenes during that waiting period, I believe, is different than in most other ICE vehicles and this thread's focus. If I've got it wrong, do correct.

    A fair number of you know this and another group just wants to know the procedure, not what's happening. This post is for those who want to know how and why. It's long, but there's nothing I feel I can drop from it.

    Before explanations you'll have to except some facts. And before hearing those facts you'll have to understand some basic electric concepts many of you may already know:

    Concepts

    What's a relay? It's an electronic switch. "Oh, like the one on my wall that operates the lights?" No. That's a manual switch. It controls electronics--true-- but you manually exerted the effort with your fingers to change its state. Relays are all over the place, especially in vehicles. They come in handy when two electric devices work in tandem, but run on different electrical systems, sometimes at different voltages, or even alternating versus direct current. Example, when utility A/C power drops at home, a switch tells the generator to turn on, and crank off its D/C battery. There's more to relays, like N.O. and N.C ones (normally open/normally closed) but beyond need to understand here.

    What's a parallel connection between batteries? Its when all the negative terminals of two or more batteries are connected together to form one negative, and the same happens separately for all the positive terminals. Voltage remains fixed, amperage is increased. That's the layperson's explanation.

    Electric Facts in the 3.6L JL

    • There are two batteries, a smaller one tucked away: the ESS (Engine Start/Stop) or Aux battery if you prefer, and a main one. This is well and better discussed in other posts.
    • These batteries are always hooked up in parallel (99.9% of the time) except when:
      • The ESS system is engaged. In this case your main battery rests and your ESS battery runs things like the radio and lights.
      • The engine needs to crank, be it a cold start in your driveway, or when taking your foot of the brake as the traffic light turns green, or the 3.6L takes you out an ESS event because the ESS battery is running low, and in either of these latter two cases (foot off brake or low ESS battery), the 3.6L takes you out of an ESS event.
    • At the point where the engine needs to turn over, regardless of whether you push the start button, or take your foot off the brake at a just made green traffic light, during an ESS event, or the ESS battery becomes discharged during an ESS event and the 3.6L automatically takes you out of the ESS event or you remote start the 3.6L JL with your accessory remote start on your key fob:
      • The 3.6L breaks the (parallel) link between the two batteries.
      • A test of the ESS battery's current is effected. If inadequate, the start process fails.
      • The ESS battery becomes solely responsible for energizing a starter relay, which tells the starter to work.
      • The two batteries are reconnected back into parallel, and then....
      • The starter is energized by both batteries (because they're back in parallel) to crank the engine.

    But why?

    • The main battery is saved during an ESS event to bear the primary responsibility for turning the energy drawing starter. Once the engine cranks, the batteries are recharged from the alternator, powered itself from the engine. This is why an ESS event may end early if the ESS battery becomes too discharged: it still needs enough power to energize the starter relay.

    The implications

    • You could replace your main battery with one producing 12V and capable of delivering 7 trillion amps, coming right off the steam turbines of a nuclear power plant, but with no ESS battery power, you get no crank. Conversely, remove the main battery, and your 3.6L should work provided the ESS battery has enough power to energize the starter relay AND crank the starter.

    The hack

    @Jebiruph has posted and explained a great method whereby the batteries always remain connected in parallel. It's only 2 **possible** concerns for me is that if you allow ESS to engage with this hack, power is drawn from both batteries during an ESS event, leaving the main battery less capable of powering the starter. It is a theoretic concern of a technique Jerry researched, tried, tested, reported, and we benefit from. Second, the 3.6L ***may*** be allowed to enter into ESS mode, even if the ESS battery is low, possibly getting a false higher reading because of its permanent parallel connection to the main battery with this hack.

    (Other Chrysler rigs with ESS and one battery do this without problems, and I can't see this hack hurting the 3.6L, although your dealer may not love it. I want to make it clear, IMHO Jerry deserves cudos, not critiques.)

    Edit: I don't think I properly and expressly conveyed the beauty of Jerry's hack, which is this. With it, the batteries are always connected in parallel, 100% of the time (not 99.99% of the time) and no longer is the starter relay dependent on the ESS battery alone having enough energy to make it run. Either/both batteries are capable of doing this with his hack.



    The jump start at last

    That's just it. You're not just jump starting. Hook those cables up as usual and wait a few minutes, and what's happening is that you are charging both batteries, most importantly here the ESS battery. True, the same is happening during the waiting period in a one battery vehicle jump start but it's not really that your allowing the donor vehicle's battery to charge here. Rather you're allowing the ESS battery in the 3.6L JL to build up current. Parked on your driveway those batteries are in parallel. So the charge to your main battery is flowing to your ESS. And that's important because in a moment you're going to press that start button, the 3.6 JL is going to isolate those batteries under your hood (and as result of following the manual and connecting the jump start leads to the main 3.6L battery, the donor battery from the ESS battery) , and the ESS battery on its own, as discussed above, will be responsible for energizing the starter relay.

    This may explain why your off the shelf portable chargers don't work (well) here. They tend to be designed to offer lots of current in a short period of time to energize the starter, not charge the batteries (drawing out current from these power packs) and THEN energizing the starter.

    Final Thoughts

    Can you just directly connect the jumpers to the ESS battery and get going quicker short of digging that sucker out (it's quite well buried under the hood)? I don't know. @Jebiruph might.

    Peace. : - )

    ~~~~~~~~~~~~~~~~
     
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  2. multicam

    multicam Well-Known Member

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    #2 Apr 16, 2019
    Last edited: Apr 16, 2019
    True pioneers, you and @Jebiruph and @Rhinebeck01 (remind me if I’m missing anyone)! History will remember your work, and generations of JL owners will reference it in dark times.
     
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    Rahneld

    Rahneld Well-Known Member

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    Thanks, nonsense. All the credit goes to @Jebiruph, next to @Rhinebeck01.

    At best, because I'm stupid, I'm good at duming it down for me and the rest of us novices.
     
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  4. melendez69

    melendez69 Well-Known Member

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    It's a great read in language & small words I can understand (and I thank you for it). But you do the electricity stuff, and leave the spelling to the rest of us. ;)
     
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  5. Jebiruph

    Jebiruph Well-Known Member

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    Here's my diagrams of the starting system relays, the second one shows which battery powers what. As soon as the batteries are reconnected, both batteries power everything, so can you explain with the diagrams how it works?

    starting relays 1.PNG starting relays 2.PNG
     
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  6. OP
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    Rahneld

    Rahneld Well-Known Member

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    Thanks Jerry. @Jebiruph These diagrams are great and reflect the hard work you did and then communicated with the rest of us.

    At best, all I'm capable of doing in terms of adding value is making it an easier read for the rest of us, and maybe draw some conclusions from it in similar easy speak.

    If I reflect the mindset of some who benefited from my post, I will humbly admit, upon reading these weeks ago, that the only thing labelled "IBS" that I knew of was Irritable Bowel Syndrome.

    That's on me, not you, and inspired me to better do my research to better understand (your) electrical schematics, and how things like IBS stand for Intelligent Battery System.

    Also, sometimes schematics like the above don't explain well the order in which things happen. Again, that's not on you. You're the man! : - )

    Peace. : - )

    ~~~~~~~~~~~~~~~~~
     
  7. Stickerhead

    Stickerhead Well-Known Member

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    So can we just go back to a single battery if we do not use the ESS without any repercussions?
     
  8. OP
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    Rahneld

    Rahneld Well-Known Member

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    Even if you permanently insure ESS to never engage, be it because you religiously press the ESS button "on" (i.e. disabling ESS) after each cold crank, or buy technology (e.g. JL Tazer) to do it for you,

    by no means are you any less wedded to your ESS battery.

    You still need, it,
    unless--and I may be wrong here, you employ @Jebiruph's well documented hack that jumpers terminals N1 and N2 on the right side of the Power Distribution System (PDS), closest to the front of the 3.6L JL, where the PDS is itself located closest to the firewall and on the passenger's side of the vehicle.

    I urge you, if you go this route, to follow Jerry's steps and connect the two points with a fuse.

    To rehash the important stuff:

    ESS system on or off, and if off: whether your doing, or the 3.6L JL's (e.g. because you didn't meet one of the criteria with the brake pressed and the rig cranked: like lack of warm engine....):

    • When you attempt to crank that engine by remote start or pressing the start button with your foot on the brake, (or an ESS event ends) the ESS battery is isolated and must have sufficient power to energize the starter relay to "tell" the starter to work.
    • True--the batteries are rejoined in parallel just after the starter relay fires, and prior to the starter doing its work, but no ESS battery, no relay communication, no starter work and no engine crank.
    • As Jerry's hack hooks the batteries up in parallel 100% of the time, even when the JL, as from the factory, [attempts to] sever that parallel connection for the starter relay to communicate, his hack ***may*** be how you can get away without a ESS battery, or at least a non-working one, because the main battery can energize the starter relay.

    But why, and how did this come to be?

    Fellow forum members, I'm going to make up a hypothetical conversation on how this system ***may** have been designed as if we were a fly on the wall at engineering meetings at FCA about 3.6L JL gas mileage. I could be entirely wrong. The dialogue is here to make a point that hopefully leads to better understanding.

    FCA Engineer 1: We need to improve the JL's mileage!

    FCA Engineer 2: An ESS system may take the edge off those requirements.

    FCA Engineer 3: That's great but the JL has no minivan like ESS requirements. For example, when stopped at a traffic light with the engine off and many of our users outfitting their rigs with energy intensive accessories, it might be a bad idea to run the ESS off of one battery like in other vehicles. That battery's going to drain, and then when it comes time to crank the engine when the traffic light turns green, little energy will be left in that battery to energize the starter.

    FCA Engineer 4: OK, no problem....so we don't engage ESS if the battery is low, and if ESS is engaged, and if the battery drops too low, we turn off ESS before the user takes their foot off the brake, crank the engine and get the alternator to recharge the battery.

    FCA Engineer 1: Ok, we all know that such drains on a battery aren't good for its life. Let me take this to the bean counters.

    Next day:

    FCA Engineer 1: OK everyone, the bean counters are worried we are going to be swapping out batteries under warranty and causing bad blood when out of warranty ones die faster with this design. That's going to cost us either way. We're on the right track here but we need to make some tweaks.

    FCA Engineer 2: OK, let's introduce a second small battery. It keeps everything going during an ESS event so the big battery can crank the engine. Same rules: If the ESS battery is low, we don't engage ESS. If it gets low during an ESS event we start the engine with the big battery.

    FCA Engineer 3: Great, but when you transferred all electronics over to the ESS battery during an ESS event you created two distinct power systems: 1) those things which runs on ESS and 2) all else. How are you going to get them to talk to get the starter to work?

    FCA Engineer 2: How do we ever get two distinct electrical systems to talk?

    FCA Engineer 1, 2, 3, and 4 in unison: With a relay!!!

    And everyone left the meeting happy. The ESS battery would start the process of turning over the 3.6JL after an ESS event, in fact while the engineers we're at it, to save costs, they made this apply for a cold crank as well.

    So pleased with their work they said, "what do we have to worry about?" If the ESS battery dies or is low, ESS will never engage. If it all but dies during an ESS event when the two batteries are seperated, because we're monitoring that ESS battery during the ESS event, in its last dying breath we'll get it to engage the starter relay, which takes milliamps (i.e. nothing) to fire, and we'll take the 3.6 JL out of ESS with the big battery and engine and alternator.

    One Junior Engineer, who rose through the ranks with a monkey wrench in his hand, not a degree, said, "yeah, but you've devised a system whereby if the ESS battery dies, the 3.6L won't cold crank!"

    The Senior Engineers laughed. The bean counters were happy that only a small battery might need replacement: something the Engineers felt wouldn't happen anyway. In hindsight, and I've given Ted Kunikis plenty of my words on this, the computer should have been programmed to say:

    If cold crank, both batteries power the starter relay.
     
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  9. LincolnSixAlpha

    LincolnSixAlpha Well-Known Member

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    Nice Write-up... However, I've been successfully defeating my ESS for months now, happy as a clam, with my TaserJL mini. What I'd love to do is rip out that ESS battery and any associated electronic nonsense and just get back to basics. I've not done any research into this as of yet because.... well.. motivation, rather lack thereof. That said, I would like a simple setup, 12V system with one battery that I can throw a booster starter on without fear of it not working properly.
     
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    Rahneld

    Rahneld Well-Known Member

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    Hey Brian:

    Since you and it seems poster @Stickerhead would both like to rip out your ESS batteries--and I don't blame you, I bet you're not alone--I'm going to address this again with two approaches. This is on me, and probably because explanations like mine above were (and I think had to be) long winded.

    The first, simpler approach is to just rename the "ESS/Aux battery." The second approach is a brief revisit as to the "whys" of the matter.

    The first simpler approach

    Here ye here ye, I call to order the naming committee for the 3.6L JL. I motion that we change the name of the "ESS/Aux" battery to the following:

    "The battery that gets your rig started every time you cold start it****, and echem, on a latter note, the battery that also happens to run ESS if you haven't disabled it and the conditions are good for the JL engaging it."

    **** @Jebiruph's hack, I believe, notwithstanding:

    https://www.jlwranglerforums.com/forum/threads/3-6l-ess-aux-battery-bypass.17293/

    Now Brian (and others) you wouldn't rip out a battery that gets your rig started would you? ; - )

    The slightly less simpler second approach

    When you cold crank, the ESS battery was designed from the factory to solely be responsible for telling the starter, through the starter relay, to crank the engine. If your ESS battery dies when you park, you're not cranking without a jump start. Nothing changes about that based on the ESS system's engaging or ability to engage or whether you disengaged it: manual or with technology like the JL Tazer or SmartStopStart. Only Jerry's link above, I believe, can change that.

    The heart of the matter

    You want a simpler jump start scenario especially since you don't intend on using ESS. Okay. You have two options.

    1) Implement Jerry's hack linked above so cold starts tap both batteries for all aspects of the crank. (Out the factory both batteries power the starter but on the ESS battery powers the starter relay.) This will make you less likely to not cold crank because both batteries will always operate everything in parallel. I see no downside to it except, maybe, if you choose to allow ESS to engage with it. And whys on that...I can provide links upon request.

    2) Implement Jerry's jump start hack here:

    https://www.jlwranglerforums.com/fo...y-consolidated-information.25377/#post-602294

    Which I believe will temporarily, and for good reason, bypass hack #1, so power can be concentrated on that battery with "the incredibly long new name we just gave it" formerly known as the ESS/Aux battery.


    A quick explanation of #2

    Option #2 isolates the battery that gets your rig started every time you cold start it, and echem, on a latter note, the battery that also happens to run ESS if you haven't disabled it and the conditions are good for the JL engaging it (a.k.a. the ESS battery---see what I did there, I used my definition so it will catch on).

    This allows it to charge much faster than not removing cables and putting your power pack leads on the main battery, which will charge both batteries, slower, and might not leave enough power in the power pack to crank the engine.

    Peace : - )

    ~~~~~~~~~~~~~~~~~~~~

    (I don't want to change the name of the ESS battery except when understanding the concepts.)
     
  11. Stickerhead

    Stickerhead Well-Known Member

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    Jerry’s bypass just connects them at all times. Can the ESS battery be completely removed, a nice good main battery be installed and the ESS permanently be disabled? If the ESS battery is only used during ESS stops, I don’t see any reason it can not be removed as long as the ESS is no longer in service. This would be a normal battery setup. If am never going to use the ESS function.
     
  12. chessiehokie

    chessiehokie Member

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    Might this entire two-battery setup have been put in place as a precursor to the eventual adaptation of eTorque/BSG on the 3.6L? It seems that would establish the basic circuitry that eTorque will use to support ESS, thereby simplifying the manufacturing changeover. My understanding is that the smaller ESS battery is removed from the eTorque implementation on the RAM 1500 3.6L with eTorque as well as the 2.0L Turbo with eTorque, with the 48 volt battery responsible for cranking while the 12 volt standard battery continues to power accessories, etc.
     
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    Rahneld

    Rahneld Well-Known Member

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    I think so. I haven't tried it. I'm not even sure you'd need to go out an by a bigger main battery as you're not (as per above) going to be allowing the ESS system to engage. If you've got no ESS battery then it's not as if your main battery is going to be parasitically drained by a bad ESS battery connected in parallel.

    Definitely try it nearby. Have extra fuses on hand for Jerry's hack. I cannot guarantee you that it wouldn't make lights flash on the dash or that you may even encounter something I hadn't considered.

    But aside for the potential for parasitic drain from the main battery to the ESS battery, particular when the 3.6L JL is parked, why get rid of it with Jerry's hack?
     

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