Voltage 12.8 to 14.2

[JTGuy]

I noticed today that my voltage is going from 12.8 to 14.2 for no reason while running. It's the original pair of batteries and the ESS has been off for a while with the Tazer mini. Everything works and no codes or trouble lights. Today I drove 150 miles with it. Could they be starting to fail?

Sponsored

 

[JW Jeep]

Sounds to me like they are about fully charged after that 150 mile run. Mine has also done that.

 

[ShadowsPapa]

I noticed today that my voltage is going from 12.8 to 14.2 for no reason while running. It's the original pair of batteries and the ESS has been off for a while with the Tazer mini. Everything works and no codes or trouble lights. Today I drove 150 miles with it. Could they be starting to fail?

Check the other threads on the way voltages vary on modern vehicles.
If the batteries are at or near full charge, and/or hot, the voltage will be cut back.
If you are coasting and not under a heavy load and the batteries need a bit of a boost, the voltage will climb and could go to 15.0 in cold weather
ESS has nothing to do with it, Tazer has nothing to do with it. Shutting ESS off won't matter.

I've posted some of these charts in various places.
If your voltage never changes - it's more likely to be a problem. changing voltage is pretty normal.

 

[ecidiego]

Totally normal.

 

[Hootbro]

Voltmeter is like the oil pressure gauge, best to stop looking at it until you actual might be having a problem. It is going to vary quite a bit and will be wasting a lot of time worry about nothing.

 

[legacy_etu]

Voltmeter is like the oil pressure gauge, best to stop looking at it until you actual might be having a problem. It is going to vary quite a bit and will be wasting a lot of time worry about nothing.

^^^ this. I was watching mine for a while wondering why is it fluctuating so much and worrying if something was about to happen. Yes, I knew all about the smart charging system. Finally I stopped watching it when I realized everything seemed fine and there weren’t any weird symptoms of anything wrong.

 

[ATL_Rubi]

^^^ this. I was watching mine for a while wondering why is it fluctuating so much and worrying if something was about to happen. Yes, I knew all about the smart charging system. Finally I stopped watching it when I realized everything seemed fine and there weren’t any weird symptoms of anything wrong.

I like to watch it while the ESS is active and see how low it’ll let itself get before cranking back on. Seen it hit 11.7 a time or two in the summer.

We’ve got a few cars with lithium ion batteries, those voltages hang in the 15s for quite a bit before pulling back current.

 

[Lost1wing]

You said that you have ESS selected off with Tazer. What does it say on the ESS page when you select it on?

 

[ShadowsPapa]

I like to watch it while the ESS is active and see how low it’ll let itself get before cranking back on. Seen it hit 11.7 a time or two in the summer.

We’ve got a few cars with lithium ion batteries, those voltages hang in the 15s for quite a bit before pulling back current.

If the batteries are otherwise healthy but not fully charged, if an ESS stop is taken out to its max time, it can drop that low.

As far as 15 - I see it all the time in the winter temperatures IF my batteries are not at full charge and it's below somewhere in the upper 30s for temperatures.
The other day it was hanging around the 15.0 mark, about 37 degrees or so and I decided to check the battery voltage, engine off. 12.43 - unloaded probably would be 12.5 or so, not fully charged.
So I decided to plug in the BatteryMinder for a bit as I wasn't giving it enough long drives to get them charged in winter temperatures (even a normal battery charger will take a whole lot more time if the battery is sitting COLD so you can't expect a vehicle charging system to do any better)

^^^ this. I was watching mine for a while wondering why is it fluctuating so much and worrying if something was about to happen. Yes, I knew all about the smart charging system. Finally I stopped watching it when I realized everything seemed fine and there weren’t any weird symptoms of anything wrong.

It's like any other tool or gauge or whatever - it only has meaning if you know what's behind it all.
It was more simple in the 1980s and earlier - 13.8 - 14.2 typical running voltage, battery full at 12.67 or so (each cell of a flooded cell L/A battery back then about 2.12 or so volts, would have to look up beyond the hundredths point!)
So if at rest it was sitting 12.6, you were good. If running it was keeping up 13.8 or so, you were good. Wow, that was easy! Or was it? The electronic voltage regulators, starting with Motorola in the mid-1960s used a thermister in the regulator circuit to kick up the charging voltage in colder temps (I have the charts for that) because it was known you can't charge a cold battery at normal voltages in the same short periods of time - it takes more voltage, more time. That screwed some people up back then, too - but fortunately, most systems didn't even have volt meters - they had the ammeter. If it was on the plus, life was good. If it was below center to the negative, time to question it. Still, what if it hung up at the strong side of positive? Even then, you had to know what it could mean. The idiot light - that's better. it's either working or it's not - no clue if it's charging at 16 volts or not - all they knew was that the light was off, it's charging - until their battery was empty of fluid and swollen or they burned out headlights.

Today, we have measures of battery temperature, internal resistance calculations, formulas for capacity, health, mA out, mA back in, engine loading and more going into it.

It's still a very useful tool - if I continued to see 15.0 volts when it hits 70 again - I'm going to go in and do some digging. If I saw 12.8 at 20 degrees after sitting overnight - I'd probably be doing some digging.
While driving, it's going to be up and down - based on throttle position percentage, engine load, ambient temperature, historical data on the battery and more.

My take - observe, make mental notes as to exactly WHEN or under what conditions various things are seen - and ask questions. I go downhill, foot off throttle and voltage goes up to 14 - is that normal - for example.
Or, It was doing 14.5 but now as I give it some gas it drops to 13.0 - is there a loose wire or something? No, it lightened the load on the engine to give you back some fractions of a horse power.
Long 15 hour drive from CO back to Iowa, warm day, running radio, AC and more and the voltage drops to 12.6 - oops - it's no longer charging. Yeah, that's fine - battery full and HOT, so to preserve power and not overheat the battery, cut voltage back. That's a good thing instead of still cranking 14 volts at a hot, fully charged battery.

 

[JTGuy]

Great, my mind is at ease now. All is well. I'll know there is a problem when it doesn't start. I carry an emergency start battery all the time.

 

[Mr._Bill]

Great, my mind is at ease now. All is well. I'll know there is a problem when it doesn't start. I carry an emergency start battery all the time.

When you start getting the ESS or Aux Switch unavailable messages, then it is time to look at replacing the batteries.

 

[ShadowsPapa]

When you start getting the ESS or Aux Switch unavailable messages, then it is time to look at replacing the batteries.

By the time you get the aux switch message - the voltage there is pretty low! I believe it's around 11.7 or so. That's basically a discharged battery..........

 

[chorky]

I like to watch it while the ESS is active and see how low it’ll let itself get before cranking back on. Seen it hit 11.7 a time or two in the summer.

We’ve got a few cars with lithium ion batteries, those voltages hang in the 15s for quite a bit before pulling back current.

What cars do you have that have lithium batteries? Are they vehicles that came that way or ar you talking about just swapping lithium into the regular stock battery location? If it is the latter you are risking problems and a potential fire.

 

[ATL_Rubi]

What cars do you have that have lithium batteries? Are they vehicles that came that way or ar you talking about just swapping lithium into the regular stock battery location? If it is the latter you are risking problems and a potential fire.

Sports cars with stock Li-ion’s. Specifically 3 of them, our 991.1 gt3rs, huracan and 650s.

 

[chorky]

Sports cars with stock Li-ion’s. Specifically 3 of them, our 991.1 gt3rs, huracan and 650s.

Wow, that's pretty cool. First I have heard of a stock battery being lithium.

Sponsored