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Drained Battery, Any jumpstart tips??

Rahneld

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I'm at the dealer, first initial test shows both batteries are gone.
Gone as in dead, or gone as in unable to even hold a charge?

If the first case, in the 3.6L JL, one should expect nothing less. 99.9% of the time the two batteries are connected in parallel.** If one of the batteries is defective and dead, it may tax the other battery for "juice," in a fruitless attempt for charge that drains the good battery.

** When are they NOT connected:
  • For an instant during an engine crank: cold or ESS: where the ESS battery, on its own, signals the starter to draw current from both it and the main battery after the two batteries are reconnect in parallel. (Read: the starter is energized from either/both batteries.)
  • During an ESS event.
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jlsahara

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Gone as in dead, or gone as in unable to even hold a charge?

If the first case, in the 3.6L JL, one should expect nothing less. 99.9% of the time the two batteries are connected in parallel.** If one of the batteries is defective and dead, it may tax the other battery for "juice," in a fruitless attempt for charge that drains the good battery.

** When are they NOT connected:
  • For an instant during an engine crank: cold or ESS: where the ESS battery, on its own, signals the starter to draw current from both it and the main battery after the two batteries are reconnect in parallel. (Read: the starter is energized from either/both batteries.)
  • During an ESS event.
Batteries couldn’t hold a charge. Replaced both.

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WranglerMan

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I'm at the dealer, first initial test shows both batteries are gone.
Batteries do go bad and several here have had them replaced but I’m more curious as to the cause, do you have any add ons like winch, off-road lights etc.... that would cause a parasitic draw
 

jlsahara

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Batteries do go bad and several here have had them replaced but I’m more curious as to the cause, do you have any add ons like winch, off-road lights etc.... that would cause a parasitic draw
Nothing aftermarket is connected to my AUX or battery. No lights or winch. I do have a Tazer left connected but it was on 11.08 (I think that’s it) and only used the tire size and DRL features on it.

I have no clue. Had the vehicle 13 months.
 

WranglerMan

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Nothing aftermarket is connected to my AUX or battery. No lights or winch. I do have a Tazer left connected but it was on 11.08 (I think that’s it) and only used the tire size and DRL features on it.

I have no clue. Had the vehicle 13 months.
My main battery went out after 7 months but has been fine since, I normally put it on a battery tender once a month when it’s parked for several days, I connect at night and by morning it’s done
 

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Rahneld

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Nothing aftermarket is connected to my AUX or battery. No lights or winch. I do have a Tazer left connected but it was on 11.08 (I think that’s it) and only used the tire size and DRL features on it.

I have no clue. Had the vehicle 13 months.
Oscar, I don't mean to split hairs sir, but unless you have a special setup, if your riding a 3.6L, 99.9% of the time your two batteries are connected in parallel....

...point being anything you have hooked up to one battery, by definition, you have hooked up to the other.

The only times on the 3.6L where the batteries are isolated are for a brief instant when the rig cranks, and during ESS events. : - )

I don't mean to be a stickler. Happy trails!
 

jlsahara

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Oscar, I don't mean to split hairs sir, but unless you have a special setup, if your riding a 3.6L, 99.9% of the time your two batteries are connected in parallel....

...point being anything you have hooked up to one battery, by definition, you have hooked up to the other.

The only times on the 3.6L where the batteries are isolated are for a brief instant when the rig cranks, and during ESS events. : - )

I don't mean to be a stickler. Happy trails!
I get that for the previous posts. I was just trying to isolate what drained the battery(s). I can't think of anything other than the ones given were defective from the factory.
 

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My Jeep did not start this afternoon. It would turn on and try to crank, but then stop/fail. I was able to jump it like (from my wife's car) with a jumper cable. Fired right up no problem without waiting a few minutes. Am I correct that my main battery is starting to fail?
 

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I jump started this morning the old fashion way, car to car. I did let it sit for several minute hooked up before trying. Worked fine. Was my fault. Left lights on over night.
 

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My Jeep did not start this afternoon. It would turn on and try to crank, but then stop/fail. I was able to jump it like (from my wife's car) with a jumper cable. Fired right up no problem without waiting a few minutes. Am I correct that my main battery is starting to fail?
Before I answer this, would you mind telling us what engine type of JL you own (3.6L, 2.0L Turbo)?
 

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My Jeep did not start this afternoon. It would turn on and try to crank, but then stop/fail. I was able to jump it like (from my wife's car) with a jumper cable. Fired right up no problem without waiting a few minutes. Am I correct that my main battery is starting to fail?
Namib: if you own a 3.6L JL my answer is that you cannot draw conclusions above which, if either, or maybe both batteries are giving you problems short of letting a tech test each one independently.

I say this for the following reasons:
  • On the 3.6L the main and ESS/Aux batteries are connected in parallel 99% of the time (including when the rig is parked.) In fact the only time they aren't connected as such is during ESS events, when the main battery is isolated and allowed to rest, and for an instant at startup when the 3.6L tests that the Aux battery, all on its own, has sufficient power, before a crank of the engine is attempted. If it doesn't, a crank is not attempted.
  • Best research by forum members on this subject matter finds that even if somehow your main battery was swapped with a "utility power plant" and the ESS/Aux battery were lacking power, the 3.6L won't attempt a crank.
  • The fact that the batteries are connected in parallel at rest, with no alternator to charge them from a running engine means either, if lacking power, could be a parasite on the other and drain it, seeking in vain to charge itself, and in so doing, resulting in both batteries being stripped of power.
  • If you disconnected the main battery and your ESS/Aux battery had ample power, cranking and running the JL will not be a problem. The converse, as per the above is NOT true.
  • At crank, provided the ESS/Aux battery has sufficient power (again, I'm talking the 3.6L) both batteries are hooked up in parallel prior to the engine crank and both can participate in providing power to crank the engine.
  • The fact that your JL cranked immediately after you hooked cables up to presumably the main battery suggests the ESS/Aux battery already had power (3.6L only).
  • In fact this wait period that FCA suggests you effect is for the purposes of charging the ESS/Aux battery enough to pass the threshold of power in it allowing the rig to proceed with the engine cranking process.
  • I can't speak to the 2.0L. It may act similarly. I simply don't know.
 

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3.6
 

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Namib: if you own a 3.6L JL my answer is that you cannot draw conclusions above which, if either, or maybe both batteries are giving you problems short of letting a tech test each one independently.

I say this for the following reasons:
  • On the 3.6L the main and ESS/Aux batteries are connected in parallel 99% of the time (including when the rig is parked.) In fact the only time they aren't connected as such is during ESS events, when the main battery is isolated and allowed to rest, and for an instant at startup when the 3.6L tests that the Aux battery, all on its own, has sufficient power, before a crank of the engine is attempted. If it doesn't, a crank is not attempted.
  • Best research by forum members on this subject matter finds that even if somehow your main battery was swapped with a "utility power plant" and the ESS/Aux battery were lacking power, the 3.6L won't attempt a crank.
  • The fact that the batteries are connected in parallel at rest, with no alternator to charge them from a running engine means either, if lacking power, could be a parasite on the other and drain it, seeking in vain to charge itself, and in so doing, resulting in both batteries being stripped of power.
  • If you disconnected the main battery and your ESS/Aux battery had ample power, cranking and running the JL will not be a problem. The converse, as per the above is NOT true.
  • At crank, provided the ESS/Aux battery has sufficient power (again, I'm talking the 3.6L) both batteries are hooked up in parallel prior to the engine crank and both can participate in providing power to crank the engine.
  • The fact that your JL cranked immediately after you hooked cables up to presumably the main battery suggests the ESS/Aux battery already had power (3.6L only).
  • In fact this wait period that FCA suggests you effect is for the purposes of charging the ESS/Aux battery enough to pass the threshold of power in it allowing the rig to proceed with the engine cranking process.
  • I can't speak to the 2.0L. It may act similarly. I simply don't know.
Just as a follow up. Replacing the main battery did fix the issue...
 

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Batteries couldn’t hold a charge. Replaced both.

4D2CA839-9A2C-4DD9-B298-DCB4DB81C7E0.jpeg

The BIGGEST QUESTION I have here is....will this happen again.

Very important.

This will determine whether the batteries are just bad (one may have help caused the other to fail)....OR....there is a electrical issue (parasitic drain) somewhere in the JL
 

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@RadicalMatt

The JL will not start if the ESS/Aux battery is depleted. This is the case even if the JL's main battery is fully charged.

I do not believe the JL responds to "Jump Starting" like many other vehicles would.

The JL needs to see the ESS/Aux battery actually charged to a certain level before it will start. As I mentioned the JL will not start even if main battery is charged if your ESS/Aux battery is depleted past a certain point.

So, if you take a regular battery charger or a trickle charger, attach to the JL and give it ample time to charge, both the Main and ESS battery will come up to a full charge in time. Once the ESS is charged enough the JL should start.

See, when you use your Jump Start Kit, the JL is never seeing the ESS/Aux battery charged and thus it will not start.

In closing.... Using a regular battery charger or trickle charger, charge the same old way as with other vehicles. Use pos and neg main battery connections points to hook the charger to. Do this and both batteries will charge. Allow ample time for charging and again, both the Main and Aux battery will charge. When the ESS battery itself, is charged enough you should see the JL start.

Note: You can separate out the ESS/Aux battery for charging....but reality is you want both batteries fully charged since you depleted both of them as you mentioned.

You can lets call it break out and charge just the ESS/Aux battery by connecting your battery charger or battery trickle charger to ground and the N5 terminal (N5 is ESS batteries pos) and charge just the ESS battery but again, you really want both batteries properly charged.

For the record, I believe the above info I have given you is spot on. I have come up with this info after lots of research. Let us know how you make out. By the way, if you have blown a high amp fuse (one that resides in PDC) you may still find the JL not starting after you charge the batteries.

.
Having the same issue and read all through the thread and realized I can't find the N5 post. So here I sit with trickle charger connected. This is not something I would recommend for taking way out in the woods, and the scary part is I already have.

For those of us without the Chilton manual, where is this mystery N5 post? Any chance of a photo?

Next, if Jeep is reading this:
1. PLEASE PUT IT IN THE MANUAL THAT STANDARD JUMP STARTING DOES NOT WORK.
2. Please fix the issue. Why do you build a vehicle with two batteries that can't sit more than a week? I am on the road often for three or more days at a time. My other two vehicles like this can sit months without sitting on a trickle charger. When the vehicle is not in use the ESS battery (or whichever you decide to use to start) should be isolated so it holds voltage. That way my manual key still works to get in.
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