HELP - 12v battery on backorder

Without a "load" on it; it shouldn't move more than a few 100th of a volt, if at all. You'll need to wait 15-20 minutes after disconnecting the charger, to let the battery settle/plates equalize before taking a reading. Make sure the battery is on a block of wood, insulated from ground - battery cases these day are getting very thin.

 

I "repaired" the old battery last night using my charger's repair mode. This morning, after 12 hours of resting, it's getting 12.63 volts?! That surprised me. That said, I'm still doubtful about its capacity at this point.

I'm going to be borrowing a load tester soon to check its depth of charge and to see how stressed it gets under load.

 

Close to 50 years of training and experience in Electronics.
But I don't give a tiny little rat's behind whether you believe me or not.
Have a nice day.

 

Why exactly would you say that ?
It is another version of an old urban myth about not storing batteries on concrete.

 

Right.
You can put a sealed motorcycle size battery in a hybrid and be fine.
The system draws ~20A for a moment during boot up of the system, then the HV battery is doing the work.

Batteries in cars are sized to provide headlights and emergency flashers for X amount of time, a Fed Spec...
And provide power for the remote RF receivers the car may have. Sized big enough where you can leave the car for weeks.
Automotive batteries may have a RC number, Reserve Capacity. This is rated in minutes with a standard 20A draw down to 10.5 VDC, IIRC. It can be derived into an AH rating.

 

Just for giggles, checked the voltage fresh off the charger this morning (surface charged to the max). This is a 6+ year Optima, has a regular charging regimen, with our low usage:

 

And that reading tells you exactly NOTHING useful.
This has been covered on here MANY times.

Let it sit untouched for 24 hours and then show us another reading.

 

Learning something new everyday..... That's what I was taught and never questioned it. You'd assume an old battery dealer would know better - that's who told me this.

 

Here is my 12v battery status as of this afternoon. This is in my 2021 PP purchased in July this year. The car is driven a few times a week for ~1hr each time, and the rest of the times parked on the driveway. I have never charged this battery. In fact, this was the very first time I opened the hood of this car. LOL

I did drive ~1 hr this morning, so it is not like my 2020 PP which sat on my driveway without being driven. The resting voltage read by my Fluke87 which is calibrated with +/- 0.05% accuracy is 12.60 volt. The load test by Ancel BA101 checked out fine with 100% Health and 98% Charge (reading was 12.63 volt which is off +0.03 volt from Fluke reading).

I can check it again later after sitting for a few days, but I really don't think there is anything to worry about the battery this new that is being driven at least once a week for ~1hour.

 

From my 2018. Taken when the car was 2 months old.


From my 2021 just a few minutes ago.


If I'm not mistaken, that corresponds to about 45% SOC for a lead-acid battery.

 

Humm, I wonder if you have more than the usual drain on your 12v battery? Didn't you say you use a computer in your car? Do you have an inverter connected to the battery?

I will check the battery again later, but on my 2020 PP, I never saw the 12v battery voltage go below 12.3v even when sitting on my driveway for more than 2 weeks and driven only once or twice a month for about ~1hr.

 

Nothing plugged in right now.

 

After yesterday morning's charger disconnect and voltage check, the car was driven maybe 3 kms. This morning, checking voltage before putting the charger back on:


Again, this battery is 6+ years old, installed in September of 2015. It's been steadily connected to a CTEK Multi US 4.3 charger, during it's frequent idle times, multiple days.

 

The external charger is key. I suspect my low voltage has to do with the car dropping the 12V system voltage from the DC-to-DC converter down to ~12.5V or below while the car is in drive (tested in the 2018 and not yet tested in the 2021). Of course if the battery were charged above 12.5V in that case, as soon as the car is put in drive the battery will become the primary source of power to the 12V systems until the charge equalizes with the DC-to-DC converter voltage.

 

That is not the observation I made on my 2020 PP while the car is in READY.
You see in my comment in this thread with the graph showing the 12v battery reading while I was driving.
12v Battery Is Discharging, Re-Charge Now ! | Page 7 | PriusChat
PP charges the 12v battery at above 14v while in READY mode, and short 50miles (~1 hours) drive was sufficient to charge the battery up to 12.78v from 12.58v.

 

About 30 hours after this — almost 2 full days since the “repair” completed — the loose battery is still testing at 12.59 volts. This is one that gave me some ‘battery low’ messages and wouldn’t hold more than about 12.1 volts after a full overnight maintenance charge while it was still installed.

 

I was wrong about the CTEK battery charger not fully charging with the battery terminals connected to the battery. I just recharged and got basically the same results as you did; 13+ volts hot off the charger and around 12.7-12.8 v after I bled off the surface charge by turning on the headlights for 30 secs.

 

Just got back from driving 98 miles today. Grabbed the Fluke right after I parked and measured the 12V battery at 12.23V. This is almost exactly how my 2018 also behaved, so I'm loathe to chalk it up to a fluke.

 

Why don't you try charging the 12v battery and see how quickly it discharges down to the current level? With my 2020 PP, it took two to three weeks to bring down the fully charged battery (~12.8v) down to 12.4v if not being driven. If it is driven at least once a week for ~1hr, it was never discharged below ~12.4v. As I said, I never had any battery problem with my 2017 PP, so I never checked the battery. For my current 2021 PP, the reading I took yesterday was the very first. I can report again in a few days, but I really doubt it will be much lower than what it was yesterday.

 

I don't have a 12V battery charger.

I have no 12V charger currently, but I ordered a CTEK to see how it goes. Maybe the batteries are sitting a long time on the dealer lot without the car being turned on and getting fouled up.