Drained Battery, Any jumpstart tips??

[brazos]

Be aware that the dual battery/Aux battery jump start related threads refer only to the 3.6 ESS system, not the 2.0. It's the same for the jumper and negative cable disconnect, it's for the 3.6, not the 2.0. From what I've read, the 2.0 does not have an Aux battery and the 48v battery will never be connected in parallel to the main 12v battery. You may still benefit from reading the battery thread I posted because it covers some very basic electrical concepts, just remember your 2.0 battery system is different.

Thanks. I’m thinking this may accompany me on all future backcountry explorations.

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[allenn]

When you say what a joke please explain, I for one have installed the fused jumper from N1 to N2 and then disconnected the ESS negative and ran several weeks like that with no issues so it effectively took the ESS battery out of the loop and all worked fine so I would think if you used the jumper and removed the ESS negative it would have been easy to jump as you are only pushing the charge to one battery

Not the jumper itself the fact that I actually had to make a jumper and Unhook the battery cable. The hack worked great. Problem was I had no jumper or tools with me and had to get on here to figure out what to do. If I wasn’t on this forum I would probably had to get a tow for a dead battery which is crazy to me. The original wiring is dumb in my opinion.

 

[allenn]

You are the first person that I've seen actually use the jumper and negative cable disconnect to get started. How did it go and what was the eventual fix to the starting issue?

It worked great. It took about 30 minutes for it to get a good enough charge to crank. The first time after I got it cranked I let it run for about 10 minutes and I took the jumper cables off and it went back dead. So then it took about another 30 minutes to get it crancked and when I got it cranked this time I hooked the negative ess cable back up and let it run with the jumper cables on for about 20 minutes and had no issues. I’m thinking maybe something in the winch was pulling power. I unhooked the winch cables and haven’t had a issue since so I’m really not sure. Sometimes I go a few weeks without cranking it but have never had a issue before and haven’t had one since.

 

[Rahneld]

As long as the dead batteries are not defective, you can jumpstart the 3.6L ESS just like a normal car, as you found. The amount of time needed for the jumpstart depends how depleted the batteries are. I have a post explaining the two battery system here. https://www.jlwranglerforums.com/forum/threads/3-6l-ess-battery-basics.20794/

Jerry: factually, I completely agree.

Maybe I'm splitting hairs but to me, a jumpstart, at least one in the conventional sense of the word, (i.e. one just like a "normal car") hooks up a ready, willing and capable battery, in parallel to a battery lacking in power to crank an engine, and nearly as soon as this hook up occurs, the dead vehicle can attempt a crank.

Here--as if I need to tell you, who's forgotten more about this than I know, barring your jumper hack, if the ESS battery is dead as well as the main one--and because the two batteries are almost always in parallel including when the JL is shut down, this would seem the more likely occurrence--the dead one draining the good one......

….time must pass for the donor battery to charge the ESS battery, as the latter will be momentarily isolated from the main battery and donor one, to, on its own, signal the main battery (and donor) to effect a crank.

Perhaps this hook up, wait, and crank is why people have referred to this as chump start--and the likely reason small portable chargers--skewed to delivery lots of power quickly, often fail to crank the 3.6L JL, having depleted much of their current first charging the ESS battery.

I'd love to see someone hook a power pack up directly to the ESS battery, isolating the main one, in a dead 3.6L, and see if that works near immediately. In theory I think it should, but if you want to crank again without the donor battery, keeping the 3.6L running for about 30 minutes, to let the alternator charge the ESS battery, as the described wait time of another poster above, might be indicated to charge the ESS battery.

...and if that ESS battery is hooked up as per factory, on the 3.6L, in parallel to a main battery that isn't charged, all that ESS charging will likely end up in the main battery.




: - )

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[Rahneld]

.....Mine is a 2.0....

Hey Joe....that's why I led with my "is this a 3.6 L JL question..." : - )

My talk centers around the 3.6L ..... : - )

 

[Rahneld]

Not the jumper itself the fact that I actually had to make a jumper and Unhook the battery cable. The hack worked great. Problem was I had no jumper or tools with me and had to get on here to figure out what to do. If I wasn’t on this forum I would probably had to get a tow for a dead battery which is crazy to me. The original wiring is dumb in my opinion.

We've had discussions about pre-making this and putting wing nuts on the N1 and N2 terminals to make connecting it when the fit hits the shan easier. Let me know if you'd like me to see if I can did up the links.

If you go the wing nut route, NO wing nut's wings may touch another wing nut's wings. : - )

 

[Rahneld]

It worked great. It took about 30 minutes for it to get a good enough charge to crank. The first time after I got it cranked I let it run for about 10 minutes and I took the jumper cables off and it went back dead. So then it took about another 30 minutes to get it crancked and when I got it cranked this time I hooked the negative ess cable back up and let it run with the jumper cables on for about 20 minutes and had no issues. I’m thinking maybe something in the winch was pulling power. I unhooked the winch cables and haven’t had a issue since so I’m really not sure. Sometimes I go a few weeks without cranking it but have never had a issue before and haven’t had one since.

Familiar with Jerry's @Jebiruph's hack, I'm not sure if the "jumper and negative cable disconnect" means your donor battery directly connected to the ESS battery, in parallel, isolating the main one.

In that case I'd expect the 3.6L to crank almost immediately after the hookup, as the dead ESS battery is connected to a good donor in parallel, but like you mentioned, it will need to charge, either from an idling engine or from your donor battery before the crank is made.

 

[WranglerMan]

If you put the jumper on between N1 and N2 and remove the ESS negative once started you should be able to remove the jumper cables and run down the road without any issues, the thing about these new vehicles and it’s not just the Jeep JL it a lot of other makers as well they all have things designed into them that give us all our creature comforts and with this comes sacrifice

 

[allenn]

If you put the jumper on between N1 and N2 and remove the ESS negative once started you should be able to remove the jumper cables and run down the road without any issues, the thing about these new vehicles and it’s not just the Jeep JL it a lot of other makers as well they all have things designed into them that give us all our creature comforts and with this comes sacrifice

I removed the jumper pretty much immediately from n1 and n2 after start up and left the jumper cables hooked up With donor vehicle and Jeep running about 10 minutes and the negative cable to ess battery was still unhooked and soon and removed jumper cables Jeep died.
Did the whole process again got it cranked removed jumper from n1 and n2 this time I hooked the negative ess cable back up
Left donor vehicle and Jeep running probably close to 20 minutes before pulling off jumper cables and Jeep never did die the second time. I don’t know if the ess negative had anything to do with it or just the fact I left the jumper cables on longer the second time to get more charge.

 

[jeepdabest]

You are the first person that I've seen actually use the jumper and negative cable disconnect to get started. How did it go and what was the eventual fix to the starting issue?

Is it easier to jumpstart the small battery instead?

 

[jlsahara]

Well, a day later and the car wouldn’t start this morning. When I jumped it yesterday I let it run for 30 mins and did a couple trips with no issue. Let it sit overnight and this morning it didn’t start. Had to jump it again for my 5 hour trip back to AZ.

I’m trying to think what I have done differently this weekend and only thing I can think of is that my wife left her spare Jeep key in the car so I’m not sure if the car was sensing it and always on? Not sure what else could have drained the battery.

 

[Rahneld]

Is it easier to jumpstart the small battery instead?

It is not "hard" to isolate the small (i.e. ESS) battery on the 3.6L JL, although a bit more to do than conventionally putting your donor battery leads on the positive and negative terminals of the main battery. There's links here on how to do this (care of @Jebiruph).

What it is though is faster in wait times. As the ESS battery and donor battery are connected in parallel in the scenario you describe, I'd expect that you can attempt to crank the JL right after hooking up the donor battery directly to the ESS battery.

The thing of it is though that the ESS battery, assuming it's not defective and can take a charge, will need to charge, and that charging can come in one of two ways.

• You can sit with the donor battery charging it before cranking, or
• You can crank your 3.6L JL and drive it for this charging duration, letting the alternator effect the charge.

What you can't do is crank the 3.6L, disconnect the donor battery, quickly shut down the 3.6L, and expect it to crank all on its own next time.

Final thoughts. Charging the ESS battery also occurs when you hook up the donor battery leads to the main battery as per the manual, but that donor battery is charging both batteries (as both batteries are connected in parallel when a 3.6L sits with its ignition off, and most other times.) In this charge method, two factors slow things:

• Charging two batteries takes longer, and
• The ESS battery needs to have enough power on its own before the 3.6L will crank. And this is because at crank, using the conventional jump start connection points to the main battery only, the 3.6L isolates the two batteries and the ESS battery solely signals the starter to crank, which gets its electric from both batteries.

Why is this system so funky?....Its adapted from how the 3.6L is taken out of an ESS event, and makes sense in that scenario where ESS never happens in the first place if the ESS battery is low, or the ESS event ends before the operator takes their foot off the brake if the ESS battery becomes low during the ESS event.

Notice that the term 3.6L JL appears many times during this post. That's because electric in other JL models (e.g. 2.0 4 cylinder) (can) behave differently.

 

[Rahneld]

Well, a day later and the car wouldn’t start this morning. When I jumped it yesterday I let it run for 30 mins and did a couple trips with no issue. Let it sit overnight and this morning it didn’t start. Had to jump it again for my 5 hour trip back to AZ.

I’m trying to think what I have done differently this weekend and only thing I can think of is that my wife left her spare Jeep key in the car so I’m not sure if the car was sensing it and always on? Not sure what else could have drained the battery.

I'd classify your problem to sit in one of two (or both) basic problem spaces:

• Something is pulling power from your 3.6L JL when it's start button is in the OFF position--or you think it's in the OFF position, or
• One or both of your batteries has problems.

..again, it could be both.

Best have the dealer look at it. They can test each battery independently as well as see if there's something drawing on the batteries** when the ignition is in the OFF position.

** notice the plural: batteries. At rest, the 3.6L has its batteries connected in parallel--in fact 99.99% of the time this is the case but for ESS events and engine cranks. This means that connecting an electrical appliance in the 3.6L JL to either battery drains both.

Broken record: this logic is for the 3.6L JL. It doesn't apply to the 2.0 4 cylinder turbo, and it very well may not apply to the Diesel or PHEV JLs when introduced.

 

[WranglerMan]

I would take your JL to the dealer and have a load test done on each battery

 

[jlsahara]

I'd classify your problem to sit in one of two (or both) basic problem spaces:

• Something is pulling power from your 3.6L JL when it's start button is in the OFF position--or you think it's in the OFF position, or
• One or both of your batteries has problems.

..again, it could be both.

Best have the dealer look at it. They can test each battery independently as well as see if there's something drawing on the batteries** when the ignition is in the OFF position.

** notice the plural: batteries. At rest, the 3.6L has its batteries connected in parallel--in fact 99.99% of the time this is the case but for ESS events and engine cranks. This means that connecting an electrical appliance in the 3.6L JL to either battery drains both.

Broken record: this logic is for the 3.6L JL. It doesn't apply to the 2.0 4 cylinder turbo, and it very well may not apply to the Diesel or PHEV JLs when introduced.

I would take your JL to the dealer and have a load test done on each battery

I'm at the dealer, first initial test shows both batteries are gone.

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