Battery Voltage.
- Thread starter Tikka
- Start date
JHZR2
Staff member
It varies with the alloys and pastes used. But 12.6-127 is reasonable.
It’s not, but the OP asked about full charge. The condition is just an estimate.
Better question: What events led up to you asking?
Around 12.6V will tell you that no cells are shorted out. It won't tell you the reserve or peak current capacity of any of those cells.
With a battery that was ideally maintained and just time to retire due to irreversible plate degradation resulting in too low a current capacity, you will still see around 12.6V charged, but that voltage will drop too low under load. I assume automotive starting battery, but it applies to any application, when the battery is no longer suited for it's requirements.
Around 12.6V will tell you that no cells are shorted out. It won't tell you the reserve or peak current capacity of any of those cells.
With a battery that was ideally maintained and just time to retire due to irreversible plate degradation resulting in too low a current capacity, you will still see around 12.6V charged, but that voltage will drop too low under load. I assume automotive starting battery, but it applies to any application, when the battery is no longer suited for it's requirements.
The voice of reason!
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Don't batteries have to be tested at a certain temperature? Obviously testing one at 30 degrees as compared to say 70 changes things.
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The battery in my truck has a resting voltage of 12.2V and has a 5/21 date sticker from wally world. Starts fine and is at 13.8-14.2 running
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Even when it was -35 it started good
The battery in my 1995 Miata reads around 11.8 volts every morning, and has for the last 5 years. Always starts the car fine. Charging voltage is around 14 volts. It's an AGM. I think there is something wrong with it, but it has been soldiering along and doing it's job for a long time.
You can only assess state of charge by voltage measurement under the correct conditions. The battery must be rested i.e not recently taken off charge or the engine run. otherwise you get a false high reading, mine reads over 13 volts just after being taken off charge. I prefer to wait a minimum 4 hours or overnight when it will then read the correct 12.7 volts. Secondly the battery should be under no load and ideally open circuit. That's perhaps unrealistic but at the very least modern cars need to be asleep. I only have to open a door and the stupid thing wakes up all the computers and draws anything up to 8 amps which will give a false low reading until it goes back to sleep again which may take 10 mins. All the caveats about voltage measurement not indicating battery health are true but on modern sealed batteries there is no way of determining state of charge other than voltage measurement.
gathermewool
Site Donor 2023
Just turn the headlights on for a minute to get rid of the surface charge.
If you can’t use a proper load tester, just listen to the starter. If the temp isn’t excessively low, the battery is fully charged, and it cranks slowly, that load test has failed.
Unfortunately, there isn’t a good way to predict mechanical failure. I‘ve only experienced a couple of shorted cells that didn’t seem to have an obvious explanation, but it does happen. I think we’ve al experienced or know someone who has had no issue until one day when the starter just clicks and fails to crank. It just happens sometimes.
With that said, another sometimes overlooked battery health indicator is how well a battery takes a charge. If you have the ability to measure voltage and current, you’ll observe that healthy battery will drop to almost no current for a given charge voltage when fully saturated. It’s not explicit, just another data point.
specific gravity, internal resistance and inductive testers can also provide useful comparison info. Like UOA, trends matter more than a single datapoint.
Hi Guys.
Thank you all for taking time to help.
My Jeep is having some issues, so i had it connected to a scan tool. I noticed the tool was only registering the Battery at 11.9v at the top of the screen. Now the engine seemed to be cranking ok that morning. With engine running the display says 14.6v. I was unsure what a healthy 12v battery should be reading. Google suggested 12.6v, which thanks to you guys seems correct.
Anyway, as the Battery is at least six years old i have changed it. I got an Excide Platinum, 100ah and 900cca.
Thank you all for taking time to help.
My Jeep is having some issues, so i had it connected to a scan tool. I noticed the tool was only registering the Battery at 11.9v at the top of the screen. Now the engine seemed to be cranking ok that morning. With engine running the display says 14.6v. I was unsure what a healthy 12v battery should be reading. Google suggested 12.6v, which thanks to you guys seems correct.
Anyway, as the Battery is at least six years old i have changed it. I got an Excide Platinum, 100ah and 900cca.
Battery needs to be load tested not voltage tested.
I have cases when battery have good voltage but when I put the load tester, it goes to less than 9 Volt.
In the US, we can bring the battery to a part store and they load test it for free, well they are expecting a sale.
If necessary, they charge the battery first.
Amazon have battery analyzer tester for cheap also, this include load tester, etc.
Mine is lower than 11.8 (sometimes 11.2 on really cold mornings) and starts the car (a V6) just fine.
What group size battery do you have in there? I had seen some with group 51 and some with group 35. It is a small engine so it is very easy to start. Had it been a larger engine like a 2.5 or something over 3.5, then you may be in trouble. The Miata is a perfect candidate for those lithium jump pack.
Hi.
I apologise for missing your post.
The Battery i bought was this one in the link. Not sure what a H8 size is.
It is fitted to a 3 litre Diesel in my Jeep.
