Battery voltage observations

[Maverickxeo]

Mine has been in that exact range since day one (2.5 years now). I have never checked the battery voltage since it was from day one, but I will now. I did think it was strange when we got a Grand Cherokee for my wife and the running voltage is more like 13-13.4 but I chocked it up to my max tow alternator putting out more power.

That's good to know!

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[Maverickxeo]

You should not need to reset the IBS. If you need a jump start or have had a dead battery, you could benefit by doing an IBS reset. Only do it after independently charging both batteries and verifying they can hold a charge. Disconnecting the connector at the IBS sensor will reset it. I would unplug it while the batteries are charging and reinstall the connector as my last step.

Nothing to see here.........Do some research on AGM battery charging profiles to see for yourself?

Also take into account your overnight temps combined with the draws these vehicles have and I see nothing wrong with 12.2V in the morning.

I figured it *might* be normal, given the electronics on these vehicles.

As I mentioned, my TJ can sit for a month and still have decent charge (normally about where my gladiator sits overnight - about 12.2V).

That's why I was a little concerned - both vehicles run AGM batteries, so I know that 12.2V is decently low, especially after the vehicle was running decently.

I should add - I don't have ANY signs or symptoms of a bad battery - it always fires right up and everything works fine (including start/stop and AUX switches).

More than anything - I was curious about the accuracy of the voltmeter on the dash. I've only ever checked voltage at the battery when the vehicle isn't running (as I said, overnight).

 

[CrazyCooter]

A whole lot of nothing. Thanks for sharing.

I wouldn't say "Nothing"......

That list of data just tells a person with an understanding how much goes into the battery charging in comparison to the old days. With a 2500 mh charging current limit, that explains how a vehicle that gets driven rarely and for then for only short trips would end up with dead batteries.

I have to put mine on a charger once in a while because it might site for 2 weeks and then only get driven 2.6 miles each way to work.

 

[J Sierra]

First picture is radio on, next is running. Radio -6.4A and charging 17.4A

 

[CrazyCooter]

First picture is radio on, next is running. Radio -6.4A and charging 17.4A

That last PID on the second pic is MOHM.........Makes me wonder IF swapping to LiFePO4 would be an OK move with the cornputer rolling with it OR would it not like it and undercharge? There is a guy on here reporting monthly on his journey with that chemistry.

 

[ShadowsPapa]

I figured it *might* be normal, given the electronics on these vehicles.

As I mentioned, my TJ can sit for a month and still have decent charge (normally about where my gladiator sits overnight - about 12.2V).

That's why I was a little concerned - both vehicles run AGM batteries, so I know that 12.2V is decently low, especially after the vehicle was running decently.

I should add - I don't have ANY signs or symptoms of a bad battery - it always fires right up and everything works fine (including start/stop and AUX switches).

More than anything - I was curious about the accuracy of the voltmeter on the dash. I've only ever checked voltage at the battery when the vehicle isn't running (as I said, overnight).

12.2 is under half charge. Sure, it will crank and start, until it won't.
I don't get people saying 12.2 is fine. It isn't.
It's hard on batteries, cuts their life down by allowing sulfation, cutting capacity.
A bad battery can start an engine until the time it doesn't. Had that happen with my car......it started great twice while using it to tension my JT winch line, then it failed to start it, voltage was at 12.4 volts.

12.2 is not fine.
Leaving it like that is going to drastically shorten it's life and is on the edge of it giving messages like aux switches unavailable

 

[Andy29847]

I wouldn't say "Nothing"......

That list of data just tells a person with an understanding how much goes into the battery charging in comparison to the old days. With a 2500 mh charging current limit, that explains how a vehicle that gets driven rarely and for then for only short trips would end up with dead batteries.

I have to put mine on a charger once in a while because it might site for 2 weeks and then only get driven 2.6 miles each way to work.

I believe that the "Charging Current Limit" will change with conditions. Maybe JSerria can test that soon. Regardless, I don't see the value of knowing that.

 

[J Sierra]

I drove from Tucson to Seattle and back with a current shunt on my jeep. Never saw more than 50A charging current. After starting the current is 50A max then very quickly goes to 15A to 20A.

 

[ShadowsPapa]

I drove from Tucson to Seattle and back with a current shunt on my jeep. Never saw more than 50A charging current. After starting the current is 50A max then very quickly goes to 15A to 20A.

Where was the shunt? Is it possible some of that was used by the Jeep itself and not "going to" the battery?

After cranking a while to start my 360 (takes some effort to get fuel to the carburetors and fill them) I can easily see 40 amps going to the battery.

I also find it impossible to believe that the charge limit on these is 2.5 amps.
You'd take many hours to charge a battery at that rate and the typical voltages these run at. In fact, you aren't going to ever charge an AGM at that rate limit. I have a feeling it's a different meaning than what it appears as.

 

[ShadowsPapa]

I believe that the "Charging Current Limit" will change with conditions. Maybe JSerria can test that soon. Regardless, I don't see the value of knowing that.

There is no way it means what it appears at face value to mean. You'll never fully charge batteries with that limit, plus, when you are running a voltage of 14.8 volts, you aren't going to have only 2.5 amps going into the aux battery or even the main. I'd bet if you had a shunt between the IBS and the main battery negative you'd see more than 2.5 amps.

IBS3 Battery Equivalent Capacity (9000-405000): 405000.000 %
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 %

 

[Lost1wing]

12.2 is under half charge. Sure, it will crank and start, until it won't.
I don't get people saying 12.2 is fine. It isn't.
It's hard on batteries, cuts their life down by allowing sulfation, cutting capacity.
A bad battery can start an engine until the time it doesn't. Had that happen with my car......it started great twice while using it to tension my JT winch line, then it failed to start it, voltage was at 12.4 volts.

12.2 is not fine.
Leaving it like that is going to drastically shorten it's life and is on the edge of it giving messages like aux switches unavailable

I'd have to look back a couple years but when I first started thinking about my JT battery, I had measured 12.2vdc. Since that time I have been checking it quite often. At 12.3vdc I put the trickle charger on it. When I swap out these batteries next month, I load test them just to see what 6 year old batteries look like. My 7 year old Grand Cherokee Battery load test good. No actual numbers were given, but the load tester under the hood said otherwise.

 

[ShadowsPapa]

I'd have to look back a couple years but when I first started thinking about my JT battery, I had measured 12.2vdc. Since that time I have been checking it quite often. At 12.3vdc I put the trickle charger on it. When I swap out these batteries next month, I load test them just to see what 6 year old batteries look like. My 7 year old Grand Cherokee Battery load test good. No actual numbers were given, but the load tester under the hood said otherwise.

My wife's JLU gave her the "aux switches unavailable" message.
I checked the battery voltage - 12.1 volts.

Before anyone else here jumps in with "maybe the aux battery was going bad....." it's a 4xe and they only have one 12 volt battery and the message has nothing to do with an aux battery, it's just a "hey, dude, your voltage is low, we are going through LOAD SHEDDING until it recovers"

 

[Flanders]

Ah, the power of wishful thinking. If only it could start your car when the battery can't.

The effect of temperature on a lead acid battery's resting voltage is pretty small and the JT's overnight draw is (or should be) a fraction of 1% of battery capacity.

Either the battery is deeply discharged or it's nearing it's end. The first case leads to the second in short order if nothing is done to correct it.

 

[ShadowsPapa]

Ah, the power of wishful thinking. If only it could start your car when the battery can't.

The effect of temperature on a lead acid battery's resting voltage is pretty small and the JT's overnight draw is (or should be) a fraction of 1% of battery capacity.

Either the battery is deeply discharged or it's nearing it's end. The first case leads to the second in short order if nothing is done to correct it.

Right - the effect is on capacity due to greatly slowed chemical activity. It won't impact sitting voltage much at all. So don't blame that 12.1 on being cold.
Now, all of that is said with a head full of oxycodone and other drugs, so feel free to tell me I'm not thinking correctly (or just full of shit).
My chemistry experiences suggest the cold cranking handicap is due to slowed chemical reactions in the cold leading to a lower ability to convert those chemical reactions into amperage output while the voltage at rest really won't be impacted by the cold. OTOH, I am not Antoine Lavoisier. (yeah, had to look up the spelling)

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