2018 ESS battery charge?

[brow]

Hi all,
From doing some searching here and online is it correct to assume that if I charge the main battery, it will also charge the ESS battery?
I have a feeling our ESS battery may be toast. We do get regular errors appear on the dash that the ESS system is not available, which I alway thought was great cause I usually turn it off anyways.
This morning jeep would not start, battery low I'm assuming.
Charged it up, now it starts.

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[mwilk012]

Replace both batteries.

 

[brow]

Replace both batteries.

Probably time for that as well, it's a 2018 with 155,000 kms original batteries. (and it's just starting to get cold up north)

 

[Reinen]

Probably time for that as well, it's a 2018 with 155,000 kms original batteries. (and it's just starting to get cold up north)

That is an extremely long lifespan for OEM batteries.
Thank them and replace both at the same time.

 

[Ratbert]

As others have said: replace both. The way they're wired results in one bad battery taking the other out with it.

 

[melman8r]

I just had to replace both on my '20 JLR

 

[Papa5]

You might consider bypassing the ess battery by disconnecting the negative cable and pulling fuse 42. Replace main battery with larger H7 and never worry about the ess battery again. I did it 2 years ago and have not had a problem since.

 

[garykk]

And, when replacing the batteries, make sure they are both fully charged.

 

[AndySpill]

Hi all,
From doing some searching here and online is it correct to assume that if I charge the main battery, it will also charge the ESS battery?

Yes; provided the ESS battery is not shot and capable of accepting a charge. This is because 99.99% of the time the two batteries are connected in parallel (positive post of main battery cabled to positive post of ESS/Aux battery, negative to negative). The only time they are separated is for an instant at cold crank (hold that thought, I'm going to circle back on it) and ESS events.

Two batteries connected in parallel (which should have same chemistry, in this case AGM, absorbent glass mat: a type of lead acid battery, and voltage) is like two columns of water connected at their base, and filling (charging one battery) one water column with water and watching both water columns rise as "water seeks its own level."

I have a feeling our ESS battery may be toast. We do get regular errors appear on the dash that the ESS system is not available, which I alway thought was great cause I usually turn it off anyways.

Your language sounds like you are wrongly conflated turning off the ESS system with disconnecting the ESS/Aux battery. They are two completely distinct things. Not that I recommend it but you can run ESS events with one battery, or disable ESS with two batteries.

That said, seeing as you are no fan of ESS events, you may wish to disconnect the ESS/Aux battery and prevent it from ever being isolated, such as in cold cranks (i.e. engine cranks as a result of you pressing the start button, not the warm cranks after an ESS event concludes.)

The easiest way to do this is to identify the two black cables that connect to the main battery's negative post. One of those cables has as its other end the body ground on the passenger's front fender under the hood. Leave that cable connected. It is the other cable that should be disconnect, and whose end wrapped in insulation. Additionally, in the Power Distribution Center (PDC), that black box near the top of the engine bay on the passenger's side, should have Fuse 42 pulled. Doing so will prevent the Power Control Relay (PCR) from ever being energized, with no error messages, and in so doing, preventing the batteries from being separated.

Now, the pre cold crank test of the ESS battery will get routed to all batteries, not just the ESS battery, of which you have only one battery connected: the main.

Do make sure you turn ESS off as well, either by button push or after market tech. It is less than advised to run ESS events on the main battery, much that just about every other ICE vehicle on the market running ESS events does so with one battery, as you could, during an ESS event, drain the main battery down to a level where post ESS event engine cranking could become more difficult. It's not likely but a cold night, an all but shot main battery, too many after market appliances running during an ESS events and a long traffic light might early terminate an ESS event when the main battery voltage drops, just as that battery proves too weak to crank the engine.

Normally, that ESS/Aux battery is what runs appliances during an ESS event, sparing the main battery to effect the post ESS event engine crank.

This morning jeep would not start, battery low I'm assuming.
Charged it up, now it starts.

A word about this. On early model 2018s without the dealer TSB 18-092-19 flash, and a dead ESS battery will prevent the vehicle from cranking. The main battery could be a "nuclear power plant," an engine crank won't even be attempted. Newer 2018s and beyond with dual AGM battery setups will fail on the first crank but on subsequent attempts try to crank off the main battery.

I would very much recommend replacing your main battery. The nature of the parallel connection I described in such that a bad battery can take out other batteries connected to it in parallel, and it sounds like your ESS battery is ready for battery heaven.

 

[brow]

Yes; provided the ESS battery is not shot and capable of accepting a charge. This is because 99.99% of the time the two batteries are connected in parallel (positive post of main battery cabled to positive post of ESS/Aux battery, negative to negative). The only time they are separated is for an instant at cold crank (hold that thought, I'm going to circle back on it) and ESS events.

Hi AndySpill, thanks so much for a great write up!
And thank you all for your responses!

 

[brow]

You might consider bypassing the ess battery by disconnecting the negative cable and pulling fuse 42. Replace main battery with larger H7 and never worry about the ess battery again. I did it 2 years ago and have not had a problem since.

Like this, AndySpill suggested as well. Do I need to push the ESS button in cab everytime I start the vehicle still? Or does pulling the fuse eliminate that?
And would I get any type of warning or fault lights at all by pulling the fuse?

Thanks!

 

[Papa5]

Still need to push the button

 

[Ratbert]

Still need to push the button

Or get a Tazer / one of the other devices that will keep it off / disable it.

 

[brow]

Still need to push the button

Bought the H7 and taped up the aux battery negative cable. Thanks all for this awesome solution!

Now just in theory (since I have other drivers in the house) what happens if the don't push the ESS button? I've trained myself to do it over the years, but hey teens will be teens....

Thanks again!

 

[Papa5]

ESS works as usual. Just off the main battery. Did you pull fuse 42?

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