Both batteries replaced at 22k mi

[SmoothOperation156]

Hi all,

I have a '21 JLUR I purchased less than 6 months ago and took it to the dealer for an oil change and a couple of items I wanted to have checked out under warranty One of the rear tail lights holding moisture, and my stop/start system never engaging with the service stop/start sometimes appearing on that page. I know stop/start is a controversial topic but I'd like to have all of the features I paid for and I figured I'd have the dealer take a look at it.

Tail light was an easy fix, they replaced it for free. Probably a micro-fracture in the housing somewhere.

I know the auxiliary battery on these JL's has had some issues so was expecting them to replace just the auxillary battery after running their battery tests. HOWEVER, they actually replaced BOTH batteries under warranty, after they BOTH failed their battery tests. I hadn't noticed any electronic issues or power issues related to the main battery so was suprised they decided to replace both batteries.

Again, all under warranty so at no cost to me. Just wanted to forward this along to any other JL owners who have any issues with their auxiliary battery, I don't know if replacing both of the batteries is a common fix or if I was a special case, but just found it interesting enough to share.

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[Reinen]

Hi all,

I have a '21 JLUR I purchased less than 6 months ago and took it to the dealer for an oil change and a couple of items I wanted to have checked out under warranty One of the rear tail lights holding moisture, and my stop/start system never engaging with the service stop/start sometimes appearing on that page. I know stop/start is a controversial topic but I'd like to have all of the features I paid for and I figured I'd have the dealer take a look at it.

Tail light was an easy fix, they replaced it for free. Probably a micro-fracture in the housing somewhere.

I know the auxiliary battery on these JL's has had some issues so was expecting them to replace just the auxillary battery after running their battery tests. HOWEVER, they actually replaced BOTH batteries under warranty, after they BOTH failed their battery tests. I hadn't noticed any electronic issues or power issues related to the main battery so was suprised they decided to replace both batteries.

Again, all under warranty so at no cost to me. Just wanted to forward this along to any other JL owners who have any issues with their auxiliary battery, I don't know if replacing both of the batteries is a common fix or if I was a special case, but just found it interesting enough to share.

A common occurrence, especially if the Jeep isn't a DD and sits parked a lot. 2yrs is when batteries start go when they don't get recharged daily and are not on a trickle charger.

Main & Aux are nearly always linked so they should always be changed at the same time to maximize their lifespans. Many dealers will try to replace only one (or are forced to because one battery is almost bad but not quite bad enough to qualify under warrantee). So it's good that you got them both under free replacement.

 

[SmoothOperation156]

A common occurrence, especially if the Jeep isn't a DD and sits parked a lot. 2yrs is when batteries start go when they don't get recharged daily and are not on a trickle charger.

Main & Aux are nearly always linked so they should always be changed at the same time to maximize their lifespans. Many dealers will try to replace only one (or are forced to because one battery is almost bad but not quite bad enough to qualify under warrantee). So it's good that you got them both under free replacement.

It’s a DD, Ive had it for 4 months and have put almost 6k miles on it. Issue could’ve been present before I took ownership of it and was missed by the previous dealer who sold it to me.

That’s good to hear that it was good they replaced both batteries!

 

[jludave]

Main & Aux are nearly always linked

Not nearly always, just always.

 

[Reinen]

Not nearly always, just always.

Not always. They are isolated during cold starts and warm starts.

 

[Rhinebeck01]

Not always. They are isolated during cold starts and warm starts.

They are hooked up in parallel. One battery will impact the other.

 

[entropy]

Hi all,

I have a '21 JLUR I purchased less than 6 months ago and took it to the dealer for an oil change and a couple of items I wanted to have checked out under warranty One of the rear tail lights holding moisture, and my stop/start system never engaging with the service stop/start sometimes appearing on that page. I know stop/start is a controversial topic but I'd like to have all of the features I paid for and I figured I'd have the dealer take a look at it.

Tail light was an easy fix, they replaced it for free. Probably a micro-fracture in the housing somewhere.

I know the auxiliary battery on these JL's has had some issues so was expecting them to replace just the auxillary battery after running their battery tests. HOWEVER, they actually replaced BOTH batteries under warranty, after they BOTH failed their battery tests. I hadn't noticed any electronic issues or power issues related to the main battery so was suprised they decided to replace both batteries.

Again, all under warranty so at no cost to me. Just wanted to forward this along to any other JL owners who have any issues with their auxiliary battery, I don't know if replacing both of the batteries is a common fix or if I was a special case, but just found it interesting enough to share.

Replacing both is the proper procedure. It is nice they did that for you, they don't always. When my stock aux died they only replaced the aux. It was a nightmare.... a few months later the main died AND took the new aux with it.... So I went aftermarket and disconnected the aux from the main, no problems since.

Whenever the auto stop start system has issues it is usually battery related. I would 100% recommend anyone to bypass the aux battery. It is super easy DIY job that takes 5 minutes. Just remember that tiny battery gets a lot of used by the ESS system and it is constantly chugging your main...

 

[SmoothOperation156]

Replacing both is the proper procedure. It is nice they did that for you, they don't always. When my stock aux died they only replaced the aux. It was a nightmare.... a few months later the main died AND took the new aux with it.... So I went aftermarket and disconnected the aux from the main, no problems since.

Whenever the auto stop start system has issues it is usually battery related. I would 100% recommend anyone to bypass the aux battery. It is super easy DIY job that takes 5 minutes. Just remember that tiny battery gets a lot of used by the ESS system and it is constantly chugging your main...

What else is used by the aux battery besides ESS?

 

[SmoothOperation156]

What else is used by the aux battery besides ESS?

Misunderstood that the bypass then just uses main battery to power everything the aux battery would've

 

[Reinen]

They are hooked up in parallel. One battery will impact the other.

Most of the time, yes. But not during engine starts. Starting the engine without imposing a brownout to the electronics is the entire reason why the Aux battery exists.

In a cold start the batteries are isolated and the Main starts the engine while the Aux supports the basic electronics.
In a warm start (ESS) the batteries are isolated and the Aux starts the engine while the main supports the electronics, HVAC, Radio and everything else that may be in use.

At all other times (including when parked) the batteries are linked so they can be recharged and share the burden of the JL's parked parasitic draw.

 

[jludave]

At all other times (including when parked) the batteries are linked so they can be recharged and share the burden of the JL's parked parasitic draw.

Yes, I think this is the point we are trying to get across. Generally when referring to the main and aux we can think of them as a combined pair. When one goes, the other is not far behind.

 

[Reinen]

Yes, I think this is the point we are trying to get across. Generally when referring to the main and aux we can think of them as a combined pair. When one goes, the other is not far behind.

Exactly why I tell everyone to replace both at the same time. The old will always over stress the new and reduce its lifespan.

But at the same time its important to know why it exists. Otherwise people won't understand what they're giving up and risking by the Aux delete.

 

[Fuel Fire Desire]

I just replaced mine at 5 years/ 58k mi after random weird electrical issues and a no start. Though, I had been getting warning signs for years. Probably 3 years ago I started getting ESS not available/ batt charging. So at about 20-25k mi and two years is when I really should have done it too.

I’ve never owned a vehicle that went through batteries as fast as a JL.

 

[Rhinebeck01]

Most of the time, yes. But not during engine starts. Starting the engine without imposing a brownout to the electronics is the entire reason why the Aux battery exists.

In a cold start the batteries are isolated and the Main starts the engine while the Aux supports the basic electronics.
In a warm start (ESS) the batteries are isolated and the Aux starts the engine while the main supports the electronics, HVAC, Radio and everything else that may be in use.

At all other times (including when parked) the batteries are linked so they can be recharged and share the burden of the JL's parked parasitic draw.

I do know how the JL/JT dual battery works..... 8-)

I'm not talking in regard to ESS and how that works.... I'm talking 2 batteries hooked together in parallel. My post zeroed i n on 2 batteries and not ESS.

With that said..... The dual batteries are hooked up in parallel and one battery will impact... does impact the other.

You can isolate one from the other, yada yada but they are hooked up in parallel and indeed they impact each other....

 

[SmoothOperation156]

I would 100% recommend anyone to bypass the aux battery. It is super easy DIY job that takes 5 minutes. Just remember that tiny battery gets a lot of used by the ESS system and it is constantly chugging your main...

Is it the same procedure for the 2.0 as the 3.6? If so is there a link or anything for instructions on what to do for the bypass? I’ve seen take out a fuse and disconnect the neg from Aux battery but want to make sure I’d be doing this correctly.

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