Aux Battery Died, Weird Results When Doing Fuse 42 / Aux Battery Disconnection

[Charles 236]

The aux negative ground goes from the main down to the aux. By moving it to the fender your just adding another grounding path to the factory location. No harm no foul.

Actually, moving the aux ground off of the IBS (Intelligent Battery Sensor) takes the charge level of the auxiliary battery out of the PCMs charging strategy. The PCM not seeing the charge level of both batteries together affects the charging of both batteries, since they are in a parallel circuit. Both charge together, discharge together, except for the very brief time when the Engine Stop Start system is restarting the engine. This is when the PCR relay separates the batteries, allowing the vehicle electrical system to be isolated from voltage spikes caused by the restart.

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[hjdca]

Note: I had a similar issue. This is what happened to me. My aux buttons stopped working and even if I charged my batteries, the aux buttons would stop working overnight. I changed out the aux battery and I still had the problem. I returned the aux battery and got another one and I still had the problem. I tested my 1 year old Odyssey main battery and it tested out OK. I changed the IBS sensor and I still had the problem. Finally, the guy at NAPA told me that to really test the Odyssey battery, it has to go back to Odyssey, so, we took it out and sent it back. It turns out that Odyssey said their battery was bad, and I got a new one. Problem solved. I bet it is your main battery.

 

[foxwalkhq]

Disconnect both batteries and measure the voltage level of each one. Anything reading below 12.2 is suspect. Separately charge each battery and see what happens. Fully charged should give a reading of 12.8 volts.

It's very likely the Main battery is the problem. The two batteries are paralleled together all the time. To determine which one is the problem, the grounds have to be disconnected and each battery checked separately.

So just today I had to go to the post office and it wouldn't start. The voltage read ~10.5.

The good news is that new jump starter is actually a beast. I hooked it up, truck started no problem.

Can I check both batteries without having to get down to the aux battery since it's below the fuse box. I don't wanna take that apart.

If so which cable on the positive goes to the aux battery?

Coz there's the thing where I saw a bunch of posts about the black cable that's supposed to be the aux ground, and then coz mine's a 22 it was the other one. I'm assuming I remove the positive and the negative cables from the main battery (the ones going to the aux) and then I test the main battery, and then test the aux battery by touching multimeter poles to the positive and negative cables.

 

[Mr._Bill]

So just today I had to go to the post office and it wouldn't start. The voltage read ~10.5.

The good news is that new jump starter is actually a beast. I hooked it up, truck started no problem.

Can I check both batteries without having to get down to the aux battery since it's below the fuse box. I don't wanna take that apart.

If so which cable on the positive goes to the aux battery?

Coz there's the thing where I saw a bunch of posts about the black cable that's supposed to be the aux ground, and then coz mine's a 22 it was the other one. I'm assuming I remove the positive and the negative cables from the main battery (the ones going to the aux) and then I test the main battery, and then test the aux battery by touching multimeter poles to the positive and negative cables.

The easiest way is to remove the negative cables from the main battery. Check the main battery using the positive and negative posts. Check the aux battery using the positive post and the disconnected negative cables.

 

[foxwalkhq]

The easiest way is to remove the negative cables from the main battery. Check the main battery using the positive and negative posts. Check the aux battery using the positive post and the disconnected negative cables.

But to charge the aux battery wouldn't I have to remove the positive cable from the main battery?

 

[ShadowsPapa]

But to charge the aux battery wouldn't I have to remove the positive cable from the main battery?

No. That's because the positive of the crank battery is connected to the aux battery through the PCR.

By connecting to the ground cable that goes directly down to the aux battery, you have electrically isolated it and can charge it without disconnecting anything else.


This is how I checked and charged my 2020's aux battery - however, you have a 2022 so you need to take the OTHER ground cable off the IBS and clamp your charger to it as in 2021 they changed which of these two cables goes to the aux battery ground terminal.

For a 2022 and later, you need to remove both negative cables and take them apart and clamp to the larger of the two cable ends. So you have to remove both nuts, take the two apart from each other and use the cable with the larger end - which goes to the aux negative.

 

[ShadowsPapa]

Note: I had a similar issue. This is what happened to me. My aux buttons stopped working and even if I charged my batteries, the aux buttons would stop working overnight. I changed out the aux battery and I still had the problem. I returned the aux battery and got another one and I still had the problem. I tested my 1 year old Odyssey main battery and it tested out OK. I changed the IBS sensor and I still had the problem. Finally, the guy at NAPA told me that to really test the Odyssey battery, it has to go back to Odyssey, so, we took it out and sent it back. It turns out that Odyssey said their battery was bad, and I got a new one. Problem solved. I bet it is your main battery.

It's as likely the crank/main as the other.
The IBS so rarely ever goes bad - in fact, it's self-testing and FCA and even those who make the IBS's say unless there's a code, it's good, just reset it by disconnecting it a few minutes.
Jeep says - IBS is not to be replaced unless there's a specific code.

Actually, moving the aux ground off of the IBS (Intelligent Battery Sensor) takes the charge level of the auxiliary battery out of the PCMs charging strategy. The PCM not seeing the charge level of both batteries together affects the charging of both batteries, since they are in a parallel circuit. Both charge together, discharge together, except for the very brief time when the Engine Stop Start system is restarting the engine. This is when the PCR relay separates the batteries, allowing the vehicle electrical system to be isolated from voltage spikes caused by the restart.

Moving the also makes little sense due to extra connections and cables between the various grounds. They'll do whatever, but the fact is - it's a placebo for the ground.
Running a positive cable up from the aux to the main removes the PCR so it can't self-test but as we've seen, if it decides the voltages don't make sense, the ESS will stop after a few ESS cycles.
Wiring the positive directly of course puts the two closer electrically, but negates all of the other research and engineering - and safety factors.
Yes, when a starter solenoid disengages, there's a fair spike, reverse, going back up the line.

Frankly, I'd leave the ground where it is, it's the best possible place, electrically speaking.

Fun when non-electricians play electrician.

 

[foxwalkhq]

No. That's because the positive of the crank battery is connected to the aux battery through the PCR.

By connecting to the ground cable that goes directly down to the aux battery, you have electrically isolated it and can charge it without disconnecting anything else.


This is how I checked and charged my 2020's aux battery - however, you have a 2022 so you need to take the OTHER ground cable off the IBS and clamp your charger to it as in 2021 they changed which of these two cables goes to the aux battery ground terminal.

For a 2022 and later, you need to remove both negative cables and take them apart and clamp to the larger of the two cable ends. So you have to remove both nuts, take the two apart from each other and use the cable with the larger end - which goes to the aux negative.

Thanks for this. It is quite odd, I wonder what their reasoning was for changing it. Maybe to desuade people from disabling the aux battery? It seems weird to hook the smaller cable up to the smaller bolt.

What is the PCR?

I'm gonna work on this today. I will check both batteries and charge them both.

What should the aux battery read when it's charged?

Update: Or not. It's raining.

 

[ShadowsPapa]

Thanks for this. It is quite odd, I wonder what their reasoning was for changing it. Maybe to desuade people from disabling the aux battery? It seems weird to hook the smaller cable up to the smaller bolt.

What is the PCR?

I'm gonna work on this today. I will check both batteries and charge them both.

What should the aux battery read when it's charged?

Update: Or not. It's raining.

Well, send some of that rain my way, please. Neighbor's well is still dry so he's still hauling water each week.

Anyway, yeah, it's weird that they made that change.
PCR is power control relay - you don't need to worry about that because it will be closed when the truck is sitting and you are charging batteries. So you can ignore that bit.

 

[Mr._Bill]

But to charge the aux battery wouldn't I have to remove the positive cable from the main battery?

No, it's not necessary. The positive cables are tied together. The charging current only flows through the battery that has the negative cable connected to the charger.

 

[foxwalkhq]

No, it's not necessary. The positive cables are tied together. The charging current only flows through the battery that has the negative cable connected to the charger.

One thing I'm still confused about. How will I know which battery is the problem?

If the aux battery is draining the main battery, the main battery will be low but the aux battery will be charged?

But how do I know if it's the main battery? The main battery would drain the aux?

Once I charge them both how do I know what the problem is? The same thing is going to happen again because it's already happened 3 times.

I can't see the voltage of each without disconnecting them from each other and testing separately.

How will I know which one I need to replace?

 

[Mr._Bill]

One thing I'm still confused about. How will I know which battery is the problem?

If the aux battery is draining the main battery, the main battery will be low but the aux battery will be charged?

But how do I know if it's the main battery? The main battery would drain the aux?

Once I charge them both how do I know what the problem is? The same thing is going to happen again because it's already happened 3 times.

I can't see the voltage of each without disconnecting them from each other and testing separately.

How will I know which one I need to replace?

Disconnect them from each other. Charge each one, let it sit for a while, then check the voltage. Fully charged should read 12.8 volts.

My charger shows when charging is complete. If the battery is bad, it will show a failure message if it is unable to charge it.

 

[biodiesel]

We fired up the Gladiator EcoDiesel yesterday after it sat for two weeks. It was about a 38*F cold start, but it had no issues starting using the remote start. The BatteryMINDer arrived on Saturday, so I'll hook it up to the battery sometime this week.

I don't know if it matters in terms of battery life, but we turn off the Start/Stop System every time we get into the Jeep.

 

[foxwalkhq]

Disconnect them from each other. Charge each one, let it sit for a while, then check the voltage. Fully charged should read 12.8 volts.

My charger shows when charging is complete. If the battery is bad, it will show a failure message if it is unable to charge it.

Looks like it's definitely the main battery. I didn't even have to leave it for a while.

My charger shows blue when it's not charging, and green when it's charging and has a function to force charging. It also has a red error light that can come on.

I checked both batteries separately with a multimeter. Aux battery is was at 12.x volts.. and successfully would charge.

The main battery was at 0-1 volts and would not go up beyond that.. I hooked up the charger to charge it but the light stayed blue as if it wasn't connected to anything.

I went to force charge it and the light turned green and charged for maybe 5-10 seconds and light went back to blue as if it's not connected to anything.

So seems like main battery is definitely dead. I'll have to replace it. Can I trust auto parts stores to know how to change the Gladiator battery with the dual system?

Seems like that is the easiest way since install is usually free and so it's no muss no fuss.

Also I work from home and get everything delivered so there are long periods that I do not drive the vehicle..

How often should I drive it in order to not kill the battery?

 

[sharpsicle]

Looks like it's definitely the main battery. I didn't even have to leave it for a while.

My charger shows blue when it's not charging, and green when it's charging and has a function to force charging. It also has a red error light that can come on.

I checked both batteries separately with a multimeter. Aux battery is was at 12.x volts.. and successfully would charge.

The main battery was at 0-1 volts and would not go up beyond that.. I hooked up the charger to charge it but the light stayed blue as if it wasn't connected to anything.

I went to force charge it and the light turned green and charged for maybe 5-10 seconds and light went back to blue as if it's not connected to anything.

So seems like main battery is definitely dead. I'll have to replace it. Can I trust auto parts stores to know how to change the Gladiator battery with the dual system?

Seems like that is the easiest way since install is usually free and so it's no muss no fuss.

Also I work from home and get everything delivered so there are long periods that I do not drive the vehicle..

How often should I drive it in order to not kill the battery?

There's really no special process for changing the main battery. As always, the person doing it should ensure the positive clamp doesn't touch anything during the process (I usually wrap it in something like a rag and tie it out of the way), but that's really it. The big thing to remember is to reset the IBS after it's changed out.

As for maintaining the battery during periods of inactivity, I would recommend a battery tender. It will do a better job of keeping the batteries in good shape than random short drives.

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