Automotive Battery Voltage -What is ur reading?

[Patrick0525]

I asked my colleague if I could measure his battery voltage.

Drove on the highway for 45 min
The car has been parked for 2hrs.
Ambient outside temperature is 35F.
No accessories on.
Battery voltage is 12.56V
Battery is two-three years old

Is this a a reasonable number?

 

[Duffyjr]

Yes for a couple year old battery, my AGM from AAP is three years old and still reads 12.5x. But I just put a new Interstate in my car and after charging it up with my Ctek the best I've seen is 12.4 but this could be the cold weather.

 

[69GTX]

Pretty darn good if you ask me at 2-3 yrs old. 12.65v is around fully charged. The last 2 batteries I baby sat for months to 2 yrs, voltage would drop to 12.15-12.35v after a day or less of sitting.....right after battery charging too. Sometimes parasitic loads immediately start working on the voltage and drop it within a couple hrs to 12.3-12.4. In your case you don't seem to have any problems.

 

[FT92]

just checked mine 2 days ago , a two year old interstate 12.6 seems to be doing ok

 

[Patrick0525]

I just checked my battery.
Parked for 6hrs.
Ambient 35F.
Battery is 12.3

Looks like it is 60% charged.

Do you think I need to buy another battery?
It is going to zero Sunday and Monday in the Philadelphia area.

https://www.energymatters.com.au/components/battery-voltage-discharge/

 

[LvR]

Originally Posted by Patrick0525
I just checked my battery.
Parked for 6hrs.
Ambient 35F.
Battery is 12.3

Looks like it is 60% charged.

Do you think I need to buy another battery?
It is going to zero Sunday and Monday in the Philadelphia area.

https://www.energymatters.com.au/components/battery-voltage-discharge/


I reckon you cannot make any statement about the battery's condition other than to say its present and doesn't have a dead/open cell ........................

If the battery was fully charged before being parked and you knew the exact chemistry of the lead plates you should be able to go further .....................else - do a load test and look at internal resistance on a decent tester

 

[StevieC]

It can depend on the vehicle as well because some are equipped with Smart Charging systems that keep the battery in a certain state of charge and some under charged state on purpose. That was the case with my 2018 Highlander. It wanted the battery volts at 12.3 to 12.5. After doing some research on it, Toyota figures it's better for fuel economy and better for the lifespan of the battery to keep it here. It also had start/stop and it never seemed troubled by the lower state of charge.

It can also depend on the battery temperature as is the case with Chrysler vehicles equipped with Battery Temperature Sensors like my Journey had. It was wicked sensitive to the battery's temperature and would go as low as 13.8V in the head waves of summer and up to 14.7v in moderate temperatures but the battery was always 12.5v - 12.6v or higher at shut-down.

Also there are clutches on some alternators and depending on how worn the clutch is or the type of clutch that can affect the charging rate and the SOC of the battery.

I have for a while now been plugging in my vehicles to a small smart battery charger when I get home for the day to keep them full and warm in the colder temperatures. Currently I'm reverse charging through my trailer hitch plug.

In the morning when the charger is in float mode and I turn it off before disconnecting it, it shows 12.67v

 

[Patrick0525]

Originally Posted by StevieC
It can depend on the vehicle as well because some are equipped with Smart Charging systems that keep the battery in a certain state of charge and some under charged state on purpose. That was the case with my 2018 Highlander. It wanted the battery volts at 12.3 to 12.5. After doing some research on it, Toyota figures it's better for fuel economy and better for the lifespan of the battery to keep it here. It also had start/stop and it never seemed troubled by the lower state of charge.

It can also depend on the battery temperature as is the case with Chrysler vehicles equipped with Battery Temperature Sensors like my Journey had. It was wicked sensitive to the battery's temperature and would go as low as 13.8V in the head waves of summer and up to 14.7v in moderate temperatures but the battery was always 12.5v - 12.6v or higher at shut-down.

Also there are clutches on some alternators and depending on how worn the clutch is or the type of clutch that can affect the charging rate and the SOC of the battery.

I have for a while now been plugging in my vehicles to a small smart battery charger when I get home for the day to keep them full and warm in the colder temperatures. Currently I'm reverse charging through my trailer hitch plug.

In the morning when the charger is in float mode and I turn it off before disconnecting it, it shows 12.67v

I have being using a battery tender too. This morning in float mode it was 13.7 prior to disconnecting. 30 minutes later, it was 13.1 and then I drove to work. Parked the car for 6hrs and the voltage now is 12.3

This is a 2014 Toyota Venza V6,

 

[andyd]

12.2 V Rat's been sitting a couple wks. I plugged in the floater.

 

[StevieC]

Charge it up when you get home and unplug it when you go to bed and then check the voltage the next day before you run the engine. It will be lower that 12.67 because of the colder temperatures but that should tell you if it's the vehicles management system keeping it at 12.3 or it's the battery itself loosing power because it's getting weaker.

 

[Patrick0525]

Originally Posted by StevieC
Charge it up when you get home and unplug it when you go to bed and then check the voltage the next day before you run the engine. It will be lower that 12.67 because of the colder temperatures but that should tell you if it's the vehicles management system keeping it at 12.3 or it's the battery itself loosing power because it's getting weaker.


Thanks and will report back. Also purchased a Bosch 24F AGM manufacted 10/2018 and delivered 11/2018
from PepBoys. Voltage reading is 12.87
Is that fresh enough?
Will put it on the Battery Tender maintainer tonite.

 

[StevieC]

AGM for automotive use will read higher than traditional lead acid. My Oddesey battery (AGM) for the Journey used to read 12.8ish volts fully charged using their brand of charger.

Make sure your battery tender is rated for AGM, if volts exceed 14.7 it can damage the battery. Not the same as traditional lead-acid.

 

[Patrick0525]

Originally Posted by StevieC
AGM for automotive use will read higher than traditional lead acid. My Oddesey battery (AGM) for the Journey used to read 12.8ish volts fully charged using their brand of charger.

Make sure your battery tender is rated for AGM, if volts exceed 14.7 it can damage the battery. Not the same as traditional lead-acid.


Battery Minder Model 12117 .... not Battery Tender.
I think it ok for AGM. Right?

 

[Patrick0525]

In 2016 installed a DieHard and replaced the wife's 2009 Lexus ES350 OEM battery which I have been Battery Mindering for last two years. It sits in the garage and it is my emergency spare.
Stopped Battery Minding last night @5pm. This morning@5AM 13.1V and tonite@5PM 12.99V It is around 40F in the garage. Not bad for a 10yr old battery.

 

[benjy]

go to batteryuniversity.com for ALL the skinny on batteries!!! a long read about many types so read what pertains to you

 

[Patrick0525]

Originally Posted by StevieC
Charge it up when you get home and unplug it when you go to bed and then check the voltage the next day before you run the engine. It will be lower that 12.67 because of the colder temperatures but that should tell you if it's the vehicles management system keeping it at 12.3 or it's the battery itself loosing power because it's getting weaker.


Drove home 1hr highway driving.
Attached to Battery Minder for 2.5hrs(fully charged)
Detached from Battery Minder at 7pm
Readings
7pm 13.1
8pm 12.87
9pm 12.78
11pm 12.76

 

[slybunda]

72 hours after being driven mine sits at 12.2v. This is the battery that was being undercharged by a dodgey alternator which had intermittent voltage drops. This has possibly been going on for over 8 months. Battery is a year old.
Always found it odd why it would turn over slower when left for a few days.
The same day i fitted a voltmeter in the car the same day i found out about the alternator issue. Voltage goes to 13.9 then drops to 12.5 then after a few seconds goes up to 14.3 then drops back to 12.6 etc.
Replacement alternator and it sits solid at 14.3 and drops down according to engine bay temperature.

 

[willbur]

How is the lower voltage 12.3-12.5 better for fuel economy? Just curious

 

[Patrick0525]

Originally Posted by slybunda
72 hours after being driven mine sits at 12.2v. This is the battery that was being undercharged by a dodgey alternator which had intermittent voltage drops. This has possibly been going on for over 8 months. Battery is a year old.
Always found it odd why it would turn over slower when left for a few days.
The same day i fitted a voltmeter in the car the same day i found out about the alternator issue. Voltage goes to 13.9 then drops to 12.5 then after a few seconds goes up to 14.3 then drops back to 12.6 etc.
Replacement alternator and it sits solid at 14.3 and drops down according to engine bay temperature.


Update:
Drove towards home:1hr highway driving, stopped by Pepboys/pickup AGM, and then home
Attached Battery Minder to OE Toyota battery for 2.5hrs(fully charged)
Detached from Battery Minder at 7pm

Readings
1/18 7pm 13.1
8pm 12.87
9pm 12.78
11pm 12.76

1/19 7am 12.7
7;30am Installed Bosch AGM -13.2
removed OE Toyota 8am 12.75

By the way, I have a Zus( amazon) usb/cigarette lighter that monitors Voltage and sends it to my iphone. This is a 24hrs run while driving from 1/17 16:02 to 1/18 15:16. I went to work(1/18 4am), drove to PepBoys and then drove home
After 15:16, I started working on the OE Toyota battery.

@slybunda, I agree with your findings, driving with alternator output @12.6 is bad, a new alternator @14.3 constant V is much better. See my pic.

I think my alternator is OK, since it charges between 13.5-14.4 when the car is running.

 

[StevieC]

Originally Posted by Patrick0525
Originally Posted by StevieC
AGM for automotive use will read higher than traditional lead acid. My Oddesey battery (AGM) for the Journey used to read 12.8ish volts fully charged using their brand of charger.

Make sure your battery tender is rated for AGM, if volts exceed 14.7 it can damage the battery. Not the same as traditional lead-acid.


Battery Minder Model 12117 .... not Battery Tender.
I think it ok for AGM. Right?



It says it's safe for AGM among other batteries: http://www.batteryminders.com/batte...-1-33-amp-charger-maintainer-desulfator/