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Can I jumpstart by positive to positive. Negative to negative?

kapk22

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I have read several threads and still don’t know the answer.

We got the main battery up to 80 % and cannot figure out how to charge the small ess battery.


Will it damage anything if I just hook the cables up positive to positive, negative to negative?
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kapk22

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Hi Kasey:

At least in the 3.6L JL, and probably others with the dual battery design you've described, the two batteries are connected in parallel at all times but an instant at cold crank and during ESS events.

This electrical fact means that any jumper cables you put on either battery's both terminals charges both batteries. For argument sake you could hook your jumper cables to the terminals of just the main battery, just the ESS aux battery, the positive of the main and the negative of the ESS, or the positive of the ESS and the negative of the main and arrive at the same dual charging scenario. That said, hooking up to the main battery's terminals is probably best but your won't damage anything simply because you did this.

If you would like to know how to just charge the ESS battery write back.

Also, what's 80%? What was the voltage, how did you test,. and how do you know you where testing just the main battery and not both?
Thank you. I ended up disconnecting and charging the main battery. Hooked all back up and it started. Now I have a check engine light and “service airbag”.
 
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kapk22

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Ok...so it sounds like, now that you've charged the main battery in isolation and reconnected it to the ESS battery in parallel as per factory, that voltage will flow from the better charged main battery to the ESS battery, while the batteries sit connected in parallel when the vehicle is at rest, no differently than two water columns of different height (a surrogate here for voltage) being connected near their bottoms and each coming to the same height.
So, I should be good??

What about the check engine light?

I drove it across town and it’s parked now. I may run back out and see if she starts okay.
 
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Kasey:

Let's, rather than talking "good," which I can't say, rather, let's talk about what's actually happening.

As we speak it is reasonable to assume that both batteries got some charge from your trip, and that some of the main battery's power is going into the ESS battery right now while the vehicle is at rest, with no alternator charging either batteries, and those batteries hooked up in parallel, just as they were when you were driving around.

How much? It depends upon how low your ESS battery is. And if your ESS battery has issues, a whole different set of factors can be at play.

Next time you crank your vehicle, if you cannot, try a second time. If you can, and the vehicle's dash lights up the ESS off light or the check engine light, your ESS battery or other components may require service at the dealer.

What kind of charger and tester where you using? It's not uncommon for 3.6L owners to put a trickle charger on the terminals of their main battery while the vehicle is at rest to charge both batteries. Of course, access to A/C power to run the trickle charger, like what might be availalbe on a home driveway, may not be accessible in a public garage. I don't know where you normally park.
Well, it’s a 2.0. Not sure if that makes a difference.

It was over at my fathers house when this happened. I’m not sure what kind of charger it was. However, it did show the percentage.
 

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kapk22

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So, I just ran out and was able to start the Jeep. The message that comes up on the screen is:

“Stop start service unavailable, service stop start system”

It’s my understanding that this is simply telling me the smaller battery is not adequately charged. No surprise there. However, I have the start stop function disabled (via tazer mini). I am wondering if the system will eventually get back to normal full charge after driving it for a while.
 
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A couple of thoughts.

As alluded to prior, consider purchasing a trickle charger from a reputable company like Noco.

Connect it to the terminals of the main battery, plug it in electrically at the other end and let it sit overnight.

That may help rid you of those warning lights.

Also know that turning off ESS via any method, does not turn off your dependency on the ESS battery. While I cannot swear for the 2.0L engine design (others can), in the 3.6L JL this battery's voltage is tested prior to cold crank. If it's low, ESS won't be allowed to engage once the vehicle is cold cranked and other conditions for ESS to occur, like a warm engine, have been established.

Alternatively, if the the ESS battery is dead, you may not be able to cold crank, at least on the first attempt. In later model 2018 or more recent 3.6L JLs, a second cold crank will be attempted off the main battery. If it is successful the dash will show an ESS off light until issues with the ESS battery are fixed, and all future cold cranks will be off of the main battery until this issue is resolved. I am assuming that similar logic exists for the 2.0L engine vehicle.

If it were me I'd try the trickle charging. If this doesn't address the issue I'd have the dealer look at the vehicle.

If you are committed to not running ESS there are excellent articles on the forum I can refer you to that will show you how to remove the ESS battery from your vehicle by rerouting its cables to the main battery. This option eliminates issues with a parasitic ESS battery, assuming that's your problem.
Very Good/helpful information. Thank You Sir!!

She did start fine this morning and still has the check engine light, along with the other light above the fuel level. I will hook it up to a good trickle charger tonight.
 

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You need to replace the auxiliary battery.
 

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A couple of thoughts.

As alluded to prior, consider purchasing a trickle charger from a reputable company like Noco.

Connect it to the terminals of the main battery, plug it in electrically at the other end and let it sit overnight.

That may help rid you of those warning lights.

Also know that turning off ESS via any method, does not turn off your dependency on the ESS battery. While I cannot swear for the 2.0L engine design (others can), in the 3.6L JL this battery's voltage is tested prior to cold crank. If it's low, ESS won't be allowed to engage once the vehicle is cold cranked and other conditions for ESS to occur, like a warm engine, have been established.

Alternatively, if the the ESS battery is dead, you may not be able to cold crank, at least on the first attempt. In later model 2018 or more recent 3.6L JLs, a second cold crank will be attempted off the main battery. If it is successful the dash will show an ESS off light until issues with the ESS battery are fixed, and all future cold cranks will be off of the main battery until this issue is resolved. I am assuming that similar logic exists for the 2.0L engine vehicle.

If it were me I'd try the trickle charging. If this doesn't address the issue I'd have the dealer look at the vehicle.

If you are committed to not running ESS there are excellent articles on the forum I can refer you to that will show you how to remove the ESS battery from your vehicle by rerouting its cables to the main battery. This option eliminates issues with a parasitic ESS battery, assuming that's your problem.
This is a charger I have access to at work. Would this be sufficient to hook up for the next 8 hours or so?

A2A53F81-2ACD-4F5B-8DBE-372E80D474BA.jpeg
 
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kapk22

kapk22

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They are junk. The fact that your warning light is still on is enough.
I just don’t want to have to go through the pain of removing that stupid thing if I don’t have to.

If trickle charging will work, it will save me the hassle and money.

I only charged the main large battery yesterday. So, if I hook the charger up to the connected system all day, presumably it would tell me if that aux battery is toast… is what I am understanding anyway
 
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Hi Kasey:

I do not see its maximum 10 amp output as one likely to fry your batteries. For regular top of charging though I'd recommend a trickle charger.

You see the latter, unlike a "bad comic," knows when to stop.

So we are both on the same page sir, you are hooking this up to the terminals of your main battery which is now connected as per factory to your ESS battery correct? It's not like before where you applied your charged solely to the main battery, correct?
This is correct. Thank You 😃
 
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Running the batteries down once assigns blame in a place most likely to not be correct. It could be, but all members like @mwilk012 and I can go by is that you describe and historical events known to happen with the vehicle.

The ESS battery has a lousy reliability reputation. I'd say if charging can't get you back to normal that you heed @mwilk012's advice and swap out this battery, ideally via a dealer who has the ability to rule out other possible issues, like stray voltage, etc.

Good luck.
Okay. Thank You again for the help.
 

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My JL is 20 months old, started getting “ESS not available, battery charging”. Took to dealer and both batteries were bad and replaced. As others have said, you small battery is probably bad (and you main battery might be going bad).
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