Battery Voltage Problem?

[ffward]

When I disconnected the main battery last night the main battery read 12.7. This morning the disconnected main battery still read 12.7. The info screen voltage with the main battery still disconnected read 9.5. Connected the main battery, without starting it, and the main battery now read 11.4 and the info read 11.4. Disconnected the main battery, it read 12.7 again and info read 9.5 again. Did this four times in a row and the readings were always 11.4 main, 11.4 info when main battery connected, 12.7 main, 9.5 info when main battery disconnected. Will try to get to the aux battery later this week to check its actual voltage. But it seems to me that the main is good, the aux is bad, and when they are connected it is pulling down the main voltage and the info screen is reading the "average" of the two???

Sponsored

 

[Mr._Bill]

When I disconnected the main battery last night the main battery read 12.7. This morning the disconnected main battery still read 12.7. The info screen voltage with the main battery still disconnected read 9.5. Connected the main battery, without starting it, and the main battery now read 11.4 and the info read 11.4. Disconnected the main battery, it read 12.7 again and info read 9.5 again. Did this four times in a row and the readings were always 11.4 main, 11.4 info when main battery connected, 12.7 main, 9.5 info when main battery disconnected. Will try to get to the aux battery later this week to check its actual voltage. But it seems to me that the main is good, the aux is bad, and when they are connected it is pulling down the main voltage and the info screen is reading the "average" of the two???

That is correct. You could try charging the Aux battery and see if it helps. Connect the charger to the positive terminal plate while it is disconnected from the main battery, and to the negative terminal. If you measure at these points with your meter, it should read what you see on the info screen with the main battery disconnected, which is the voltage of the Aux battery.

Typically, both batteries need replaced when they are about three years old. It is best to replace them both at the same time. If they are not that old, it is okay just to replace the bad one. Try giving both batteries a full charge and see if it helps any before replacing either one.

 

[Hootbro]

But it seems to me that the main is good, the aux is bad, and when they are connected it is pulling down the main voltage and the info screen is reading the "average" of the two??? [INITIAL][/INITIAL]

Your whole voltage reading experiment of checking the voltages separated and connected is about one would expect of a parallel circuit. As you have deduced, the aux is dragging everything down.

This is not the place to go cheap and only replace the AUX. Replace both at the same time and make sure to stick to a AGM series battery.

 

[jebiruph]

When I disconnected the main battery last night the main battery read 12.7. This morning the disconnected main battery still read 12.7. The info screen voltage with the main battery still disconnected read 9.5. Connected the main battery, without starting it, and the main battery now read 11.4 and the info read 11.4. Disconnected the main battery, it read 12.7 again and info read 9.5 again. Did this four times in a row and the readings were always 11.4 main, 11.4 info when main battery connected, 12.7 main, 9.5 info when main battery disconnected. Will try to get to the aux battery later this week to check its actual voltage. But it seems to me that the main is good, the aux is bad, and when they are connected it is pulling down the main voltage and the info screen is reading the "average" of the two???

Did your symptoms change? Your first post seemed to indicate that with the main battery connected, the dash voltage was different than the main battery voltage. Now with the main battery connected they both read the same as they should. Whatever the initial problem was seems to have cleared up.

By leaving only the aux battery connected over night, it alone was powering the system electronics which is not what it was intended to do and could explain it's low voltage. I would get both batteries charged and tested, then decide what to do from there.

 

[jebiruph]

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?

Both batteries are used for a cold start, but there is a brief separation of the batteries prior to the cold start to test the condition of the unmonitored aux battery. And the disclaimer on the diagram also applies to this information.

 

[ShadowsPapa]

When I disconnected the main battery last night the main battery read 12.7. This morning the disconnected main battery still read 12.7. The info screen voltage with the main battery still disconnected read 9.5. Connected the main battery, without starting it, and the main battery now read 11.4 and the info read 11.4. Disconnected the main battery, it read 12.7 again and info read 9.5 again. Did this four times in a row and the readings were always 11.4 main, 11.4 info when main battery connected, 12.7 main, 9.5 info when main battery disconnected. Will try to get to the aux battery later this week to check its actual voltage. But it seems to me that the main is good, the aux is bad, and when they are connected it is pulling down the main voltage and the info screen is reading the "average" of the two???

Where/how are you disconnecting the main battery to check the voltage?
If you are pulling the whole thing off the post of the main, yes, you have isolated the two. And like they've suggested already, that left the aux battery connected, draining it as it was the only source handling the parasitic draw of the electronics.

You can check the voltage of the aux battery by leaving the cables off of the main battery and connecting the meter to the positive of the main and the negative cables you removed leaving the main battery negative post bare.

Using the picture below - prevent A and B from touching each other -
You can charge the main by connecting to C and A
You can check the voltage of the aux battery - and charge the aux battery, by using B and C

Follow the orange path to see how the batteries are normally connected.
Exceptions - during an ESS STOP event - engine off because ESS stopped it, and, when you start the truck there's a momentary disconnect at the PCR, otherwise that is a NC - normally closed - relay.

See how with the negative cables off the main/crank battery, you can still check the voltage and charge the aux battery without actually getting to it.
Positive path to the aux battery is from positive cable at crank battery, through bus at N2, through N3 fuse, down through the closed PCR to the + of the aux battery.
That is how I charged mine and checked the voltage. I never even saw the aux battery.
I connected my AGM charger to the negative cable I took off the crank battery and to the positive cable still on the crank battery. The PCR easily handles charging currents - it does every time you start the truck, it will sure handle the battery charger.

 

[ShadowsPapa]

Connect the charger to the positive terminal plate while it is disconnected from the main battery, and to the negative terminal.

Doesn't have to be disconnected from the crank battery. Only the negative cables need to be removed from the crank battery.
I never once removed my positive cables.
As long as you remove the negative cables as I have pictured above, and do not allow them to touch the negative post of the crank battery, then you are only charging the aux battery and only checking voltage on the aux battery even with the positive cables still connected.
No reason electrically speaking to remove positive.

 

[Gren71]

I recently changed both of my batteries and found that the reading on the dash would stay in the area of 12.5. Even with new batteries.

Then I found a setting in the Jscan app

Intelligent Battery Sensor settings -> IBS minimum voltage Limit -> Set that to 14.

Now I rarely drop below 13 and im usually around 13.6- 14

I havnet messed with any of the other settings since I dont fully understand them.

 

[ShadowsPapa]

I recently changed both of my batteries and found that the reading on the dash would stay in the area of 12.5. Even with new batteries.

Then I found a setting in the Jscan app

Intelligent Battery Sensor settings -> IBS minimum voltage Limit -> Set that to 14.

Now I rarely drop below 13 and im usually around 13.6- 14

I havnet messed with any of the other settings since I dont fully understand them.

I assume you had the IBS fully disconnected for at least 10-15 minutes when you put in the new batteries, and before putting them in, you fully charged each battery then installed them and reset the IBS?

LOL - what you most likely did was tell the IBS to always go to sleep - that's what tells is to shut down.
It's normally set to 10. That means if the battery voltage gets so low it shuts things down.
Now it is going to shut down when you shut the truck off so it won't be able to monitor draw when the truck is off.
Those are things that should never be changed.

You may end up over-charging the batteries or over-heating them messing with the IBS settings.

 

[Gren71]

I assume you had the IBS fully disconnected for at least 10-15 minutes when you put in the new batteries, and before putting them in, you fully charged each battery then installed them and reset the IBS?

LOL - what you most likely did was tell the IBS to always go to sleep - that's what tells is to shut down.
It's normally set to 10. That means if the battery voltage gets so low it shuts things down.
Now it is going to shut down when you shut the truck off so it won't be able to monitor draw when the truck is off.
Those are things that should never be changed.

You may end up over-charging the batteries or over-heating them messing with the IBS settings.

meh, at least I dont get the low battery warning any more on the curt echo while towing. It was set to 12 before I changed it though.

 

[Mr._Bill]

Doesn't have to be disconnected from the crank battery. Only the negative cables need to be removed from the crank battery.
I never once removed my positive cables.
As long as you remove the negative cables as I have pictured above, and do not allow them to touch the negative post of the crank battery, then you are only charging the aux battery and only checking voltage on the aux battery even with the positive cables still connected.
No reason electrically speaking to remove positive.

Either way works to isolate the batteries. Disconnecting from the positive side is less cables to hassle with.

 

[ShadowsPapa]

Either way works to isolate the batteries. Disconnecting from the positive side is less cables to hassle with.

Less cables to hassle with......... hmm, trying to see that, I guess.

One nut either way.

And if you leave the negative side attached, you risk a short, sparks. Always best to fully disengage the grounds.

To charge the crank battery, I simply move the negative charger clamp to the top of the IBS where this cable's nut came from.

I also advocate for removing the IBS because it's a good idea to start fresh - resetting the IBS, after charging each battery independently and fully.

But it seems sooo much easier to me - to remove one nut and lift a cable back and you are ready to charge either battery by itself.

In this picture, I'm charging only the aux battery.
Seemed pretty simple to me.

 

[ShadowsPapa]

meh, at least I dont get the low battery warning any more on the curt echo while towing. It was set to 12 before I changed it though.

Coincidence.
What that does is handles the voltage at which the IBS sleeps, shuts down, conserves power.
It would have no impact on the charging voltage at all.
Apparently something else happened because that's only for controlling cycles for the IBS, minimums. It doesn't change the rate of charge.
That is programmed into the PCM and the PCM determines charge rates based on a number of engine conditions, torque output, speed, and more - plus the data from the IBS such as battery temperature, state of charge and historical data such as how much power has come out since last charge cycle.

IBS Quiescence Current Limit (-250-0 mA): -250.000 mA
IBS Minimum Voltage Limit (0-25.4 V): 10.000 V
IBS3 Charge Current Limit (0-2500 mA): 2500.000 mA
IBS3 Battery Parameterization Kind- Battery Mode: Use Battery Type
IBS3 Vehicle Battery Type (0-63): 22.000
IBS3 Minimum Charge Limit (0-100%): 35.000 %

IBS3 Battery Capacity (0-252 Ah): 254.000 Ah
IBS3 Parameterized Type of Battery Mode: Signal Not Avaiable
IBS3 Maximum OCV Voltage (13-13.33 V): 13.000 V

Note the mis-spellings in the BCM data. Sort of interesting to see that they don't use spell check in their programming.
They can spell "quiescence" but not "available" LOL

 

[Commodus]

That is correct. You could try charging the Aux battery and see if it helps. Connect the charger to the positive terminal plate while it is disconnected from the main battery, and to the negative terminal. If you measure at these points with your meter, it should read what you see on the info screen with the main battery disconnected, which is the voltage of the Aux battery.

Typically, both batteries need replaced when they are about three years old. It is best to replace them both at the same time. If they are not that old, it is okay just to replace the bad one. Try giving both batteries a full charge and see if it helps any before replacing either one.

I do not see replacing both batteries just because they are 3 years old, I have had batteries last anywhere from 5 to 8 years. This is not the case for our auxiliary battery just do to it’s size and the environment it lives in ( next to the exhaust manifold) that one I I can see needing replaced between 2 and 3 years for a good quality battery. Saying this it will depend on you catching the auxiliary going bad ( I noticed my ess not available due to battery charging and never clearing this fault) before it starts to constantly drain the main battery to a point it never gets a chance to come up to a full charge At least this has been my experience so far

 

[ShadowsPapa]

I do not see replacing both batteries just because they are 3 years old, I have had batteries last anywhere from 5 to 8 years. This is not the case for our auxiliary battery just do to it’s size and the environment it lives in ( next to the exhaust manifold) that one I I can see needing replaced between 2 and 3 years for a good quality battery. Saying this it will depend on you catching the auxiliary going bad ( I noticed my ess not available due to battery charging and never clearing this fault) before it starts to constantly drain the main battery to a point it never gets a chance to come up to a full charge At least this has been my experience so far

As I've commented on multiple times - the battery vendors even suggest lifespans of all over the map, but more than one says "3 to 4 years" while others say "4 to 5" and some say "as long as 6" but that's an "it depends" thing. These vehicles unless driven daily and for more than a typical commute of 30 minutes never fully charge the batteries. There's also a parasitic load (normal) that tends to drain them down. The constant up and down, the heat (heat is a killer) and non-use is proving that the batteries in these Jeeps don't seem to go longer than about 3 years.
If you drove it every day - and for more than 30 minutes, you'd get more life out of it.

This is a direct quote from a battery vendor on the web =
A properly maintained AGM battery usually lasts somewhere between three and four years, but this depends on the amount that you use it. Also, the amount that you drive your vehicle plays a role in how long the battery will last.

And from Optima when asked about battery life (and guess what - many of these Jeeps don't see daily use of drives long enough to actually FULLY charge the batteries) =

A vehicle that gets driven on a 20-mile commute at 45 mph every day of the year won't be as hard on a battery as a vehicle that sits most of the year and only sees occasional use. When battery voltage is properly-maintained, batteries tend to last longer. When batteries sit in a partially-discharged state for extended periods of time, batteries tend not to last as long and that's true for both flooded and AGM batteries

Others go on about keeping the batteries at a full charge. And guess what - if your AGM battery in your Jeep is 12.4 volts, it ain't even close, in fact, it's half discharged.

The key to maximizing AGM car batteries performance and lifespan is keeping the voltage in your battery properly-maintained with a quality battery maintenance device. With the advanced technology it uses and proper ways to expend the AGM start/stop battery, it can give you a longer lifespan.
They continue - and note the last part of their paragraph -
o begin with, always charge your batteries. Make it to full charge every time. What’s more, always aim for an 80% to 85% state of charge, if you have enough time, always go for a full charge. Next, make sure to use a smart charger when you charge batteries, and avoid discharging your batteries below 50%. Besides, be sure to use the most potent source. Furthermore, smart solar controllers are advisable to use and intelligent controllers can switch modes automatically. Additionally, try to minimize the voltage drop in the battery’s system wiring and use the correct float voltage, which is one of the critical sides of AGM car

Interesting - they are saying do everything that almost no one is doing. Avoid discharging below 50% - 12.4 volts is down there. So unless you drive it daily and drive it long enough to charge the batteries back up, they ain't gonna last that 5+ years.
Heat is a factor, but so is not keeping them fully charged, driving often enough and so on.

On battery pairs, it's been my experience that trying to pair up batteries of different ages doesn't always work so well......... and these operate under far from ideal conditions.

Here's another bottom line from a battery maker - and you know no one here does this! So no way they will see that long life =
If kept in a charged state when unused, the common lifespan of a 12-volt Gel or AGM battery is up to six years. After five or six years of float voltage at an average ambient temperature of 25 ºC, the battery still retains 80 % of its original capacity. Higher average temperatures will shorten the lifespan of the battery.

Up to 6 years. That's interesting as I have ordinary lead acid batteries outlast that constantly, and they sit a lot in my cars that are parked for the winter. So an AGM will last longer if you take better care of it than you do your other batteries is what they are saying.

Sponsored