Battery Voltage Problem?

[ffward]

My 2020 Gladiator would not start yesterday. The voltage on the Jeep's info screen said 11.4 volts, yet my muti meter read 12.5. I used my small jump starter and the jeep started right up and the info screen read 14.4. After driving for about an hour, I got home and tuned it off. I checked the voltage on the multimeter and it read 12.5, and this time the info screen voltage read 12.5, and it started right up. It sat overnight, and now it is doing the same thing where the multimeter reads 12.5, but the info screen reads 11.4, and it will not start. Started it with my jump starter and both the multimeter and info screen read 14.4 again. Any ideas, suggestions on what could be going on? Thanks.

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[mert34]

are you checking the main battery or the aux battery when you are putting your meter on it?

 

[Hootbro]

One battery is dragging the other down. Balance of probability, I would say it is the aux battery.

That being said, it is good practice to change both the aux and main battery for new ones at the same time.

 

[ShadowsPapa]

are you checking the main battery or the aux battery when you are putting your meter on it?

Unless he digs into the N3 fuse and isolates things, he's checking the voltage of the pair. They are connected in parallel when it's sitting there, and then again after it is running.

Any ideas, suggestions on what could be going on? Thanks.

There are a dozen threads on this very thing - I've got a thread that's over a dozen pages discussing battery voltages, charging, testing, and more.

You, however, have a weird issue where it sounds like the IBS is not reporting the correct battery voltage. The IBS is the intelligent battery sensor that sits on the negative terminal of the main or crank battery.

When charging the battery pair on these, ALWAYS connect to the chassis ground with the charger or the top of the IBS - never directly to the negative battery terminal.

Try charging each battery independently - disconnect the aux battery negative cable from the cable bunch at the main battery negative post.
Also remove the IBS from the crank or main battery - this is the one time you violate the rule of charging only through the IBS.
Charger positive to the positive leads on the crank battery, negative charger lead to the black cable that goes to the negative of the aux battery down below.
Charge the aux using an AGM capable charger - let it go through ALL phases.

Then move the charger negative to the main battery negative.
Let it go through all charging phases.
As long as the IBS was removed for at least 10 to 15 minutes, and both batteries have been charged, put it all back together.
You have just charged each battery to full state of charge and reset the IBS - by leaving the IBS disconnected with no power, it resets.
See what happens. Otherwise with that big discrepancy in the cluster voltage compared to a decent meter - I believe it needs to be looked at.

A 2020 is getting to the point the batteries are getting long in tooth - especially the cheap small aux battery used in these. But the difference in voltages between your meter and the cluster isn't good, either.

 

[Andy29847]

You can't get much info from testing a battery with a multimeter unless you disconnect the batteries from the car and check each battery separately. Even then, all you can determine is the charge state.

The Jeep battery system is complicated. I'm experiencing some problems with my Jeep and it is in the shop. I get a message, "Start Stop not working/Battery is charging." The service manager called me today and said they tested both batteries good. They believe that the IBS is defective and they are working in that direction.

Lots of good info here: https://www.jeepgladiatorforum.com/...tage-truck-off-and-at-rest.56213/post-1050365

 

[ShadowsPapa]

You can't get much info from testing a battery with a multimeter unless you disconnect the batteries from the car and check each battery separately.

While true - when they are connected in parallel you are checking the voltage of the pair.
That's true of any pair of batteries. If one is a higher voltage than the other, say one is 12.6 and the other is 12.2 then the higher voltage battery will "charge" or push to the lower voltage battery and they'll even out at a voltage in between. So he's checking the voltage of the pair.
If the aux battery is low, the main will "charge" the aux battery taking the voltage of the main battery down until an equilibrium is reached. If the one battery has a "short" then it will eventually kill both batteries.

If your meter says 12.5 the cluster had better read at least 12.3. I have never seen a difference over about .2 volt - and why would there be?

If it was my truck - I would fully charge both batteries - independently, reset the IBS, and before putting it all back together, see if either loses the charge, and just as importantly, do they both actually reach the full voltage of 12.7 to 12.8 volts.

 

[Andy29847]

While true - when they are connected in parallel you are checking the voltage of the pair.
That's true of any pair of batteries. If one is a higher voltage than the other, say one is 12.6 and the other is 12.2 then the higher voltage battery will "charge" or push to the lower voltage battery and they'll even out at a voltage in between. So he's checking the voltage of the pair.
If the aux battery is low, the main will "charge" the aux battery taking the voltage of the main battery down until an equilibrium is reached. If the one battery has a "short" then it will eventually kill both batteries.

If your meter says 12.5 the cluster had better read at least 12.3. I have never seen a difference over about .2 volt - and why would there be?

If it was my truck - I would fully charge both batteries - independently, reset the IBS, and before putting it all back together, see if either loses the charge, and just as importantly, do they both actually reach the full voltage of 12.7 to 12.8 volts.

A fully charged battery with no load can read 12.8v. The OPs batteries are still connected to the Jeep. The voltage measured will depend on the state of the battery and the load.

 

[ShadowsPapa]

A fully charged battery with no load can read 12.8v. The OPs batteries are still connected to the Jeep. The voltage measured will depend on the state of the battery and the load.

Yes, that's a given. My point was the DIFFERENCE from his reading compared to the cluster. That's just plain wrong.

Further, if both are truly fully charged, there's a minimal draw on these and my batteries in my 2020 read 12.7 shortly after charging by driving once I did the full charge of each and reset the IBS.
It didn't take a long time for them to drop to 12.6 due to the parasitic draw of the truck's electronics.
His read 12.5 which isn't bad and indicates decent voltage at rest (not full, but then the draw of the truck would take it down a bit overnight)
I'm not concerned about 12.5 - especially since that's with the truck's electronics on it. If it wasn't connected, it would be higher, likely 12.6 or so.

His reading the voltage with a meter isn't the problem - it's fine to do that. And he's getting a good voltage on the surface of things. I'd not be that concerned with 12.5 while still connected.

My problem with his setup is -

* the cluster reading is funky indicating a PROBLEM. A reading 1.1 volts below a reading at the battery with a meter? Wow, that's really bad. There's a problem just for that fact.

* the fact it wouldn't start indicates a battery incapable of handling a load. They need to be fully charged with an AGM capable charger and go from there. Voltage reading doesn't matter - it's not starting the truck.
Now it could be that the truck THINKS the voltage is too low so won't initiate the start sequence - so it could be the batteries aren't the real issue, or they could still be. But if the truck's systems believe that 11.4 volts, then it won't start no matter how good the batteries are.
Fix that first. It could be the thing is not starting simply because of what it thinks is there or not there.

The dealer can't even load test the batteries unless they have a certain state of charge. So before they can be properly tested, they need to be charged.

You can read 12.5, which is decent and above the point where ESS should work.

Sorry, but I've done automotive electric and charging systems for decades - I'm confident in where I'm at with this.

 

[Andy29847]

I'm not concerned about 12.5 - especially since that's with the truck's electronics on it. If it wasn't connected, it would be higher, likely 12.6 or so.

His reading the voltage with a meter isn't the problem - it's fine to do that. And he's getting a good voltage on the surface of things. I'd not be that concerned with 12.5 while still connected.

* the cluster reading is funky indicating a PROBLEM. A reading 1.1 volts below a reading at the battery with a meter? Wow, that's really bad. There's a problem just for that fact.



Sorry, but I've done automotive electric and charging systems for decades - I'm confident in where I'm at with this.

I am not disagreeing with what you are saying, I was just trying to clarify the "when and where" factors.

Normally, if a vehicle has good battery voltage and will not crank, then I would start looking at connections and cranking components.

The Jeep battery configuration is new to me and I don't fully understand it. Considering that, the low reading at the instrument cluster doesn't mean much to me unless it is saying the big battery is bad. I'm not sure how the circuit between the 2 batteries is configured. I have read many times that the little battery could kill the big one. I don't know if the reverse is true.

The failing of the multimeter test is that it does not measure the ability to carry load.

 

[ffward]

Yes, that's a given. My point was the DIFFERENCE from his reading compared to the cluster. That's just plain wrong.

Further, if both are truly fully charged, there's a minimal draw on these and my batteries in my 2020 read 12.7 shortly after charging by driving once I did the full charge of each and reset the IBS.
It didn't take a long time for them to drop to 12.6 due to the parasitic draw of the truck's electronics.
His read 12.5 which isn't bad and indicates decent voltage at rest (not full, but then the draw of the truck would take it down a bit overnight)
I'm not concerned about 12.5 - especially since that's with the truck's electronics on it. If it wasn't connected, it would be higher, likely 12.6 or so.

His reading the voltage with a meter isn't the problem - it's fine to do that. And he's getting a good voltage on the surface of things. I'd not be that concerned with 12.5 while still connected.

My problem with his setup is -

* the cluster reading is funky indicating a PROBLEM. A reading 1.1 volts below a reading at the battery with a meter? Wow, that's really bad. There's a problem just for that fact.

* the fact it wouldn't start indicates a battery incapable of handling a load. They need to be fully charged with an AGM capable charger and go from there. Voltage reading doesn't matter - it's not starting the truck.
Now it could be that the truck THINKS the voltage is too low so won't initiate the start sequence - so it could be the batteries aren't the real issue, or they could still be. But if the truck's systems believe that 11.4 volts, then it won't start no matter how good the batteries are.
Fix that first. It could be the thing is not starting simply because of what it thinks is there or not there.

The dealer can't even load test the batteries unless they have a certain state of charge. So before they can be properly tested, they need to be charged.

You can read 12.5, which is decent and above the point where ESS should work.

Sorry, but I've done automotive electric and charging systems for decades - I'm confident in where I'm at with this.

I am thinking it may be the battery voltage sensor that is on the negative post maybe? I'm guessing that maybe it is sending the wrong voltage reading to the computer and like you said, the computer isn't even trying to start it. I did disconnect the battery cables from the main battery and it is reading 12.6. It's getting dark here now and I can't do anything with the aux battery tonight.

 

[ffward]

And I guess my biggest concern is why the voltage reading on the battery is not the same as what the jeep "thinks it is".

 

[Tommyd]

Unless he digs into the N3 fuse and isolates things, he's checking the voltage of the pair. They are connected in parallel when it's sitting there, and then again after it is running.


There are a dozen threads on this very thing - I've got a thread that's over a dozen pages discussing battery voltages, charging, testing, and more.

You, however, have a weird issue where it sounds like the IBS is not reporting the correct battery voltage. The IBS is the intelligent battery sensor that sits on the negative terminal of the main or crank battery.

When charging the battery pair on these, ALWAYS connect to the chassis ground with the charger or the top of the IBS - never directly to the negative battery terminal.

Try charging each battery independently - disconnect the aux battery negative cable from the cable bunch at the main battery negative post.
Also remove the IBS from the crank or main battery - this is the one time you violate the rule of charging only through the IBS.
Charger positive to the positive leads on the crank battery, negative charger lead to the black cable that goes to the negative of the aux battery down below.
Charge the aux using an AGM capable charger - let it go through ALL phases.

Then move the charger negative to the main battery negative.
Let it go through all charging phases.
As long as the IBS was removed for at least 10 to 15 minutes, and both batteries have been charged, put it all back together.
You have just charged each battery to full state of charge and reset the IBS - by leaving the IBS disconnected with no power, it resets.
See what happens. Otherwise with that big discrepancy in the cluster voltage compared to a decent meter - I believe it needs to be looked at.

A 2020 is getting to the point the batteries are getting long in tooth - especially the cheap small aux battery used in these. But the difference in voltages between your meter and the cluster isn't good, either.

Does a dead battery get covered under extended warranty?

 

[Mr._Bill]

Does a dead battery get covered under extended warranty?

Batteries are only covered under the 3/36 factory warranty.

 

[jebiruph]

And I guess my biggest concern is why the voltage reading on the battery is not the same as what the jeep "thinks it is".

The batteries should be connected in parallel when you are checking the voltage, but the differing voltage readings indicate they are not. Check for loose battery cables, especially on the negative battery terminal. It doesn't seem like a blown N3 fuse, but maybe a software glitch. I would disconnect both batteries to do a power reset. How are you connecting the cables when you jumpstart?

 

[Andy29847]

This diagram (that I found by search) seems to answer all the start questions except what signals the stop/start, i.e., triggers the PDC relay. The PCR is normally closed netting both batteries hooked together in parallel. The PCR opens when signaled by the truck system that the truck has stopped. Does this mean that when you crank the vehicle in the morning that only the main battery is connected?

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