City-Data Forum What is the proper voltage for a fully charged car battery? (warranty, power)
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04-27-2016, 08:23 AM
 483 posts, read 353,010 times Reputation: 120

Quote:
 Originally Posted by eddie1278 It's not 12 volts it's 12.6 because each cell is 2.1 volts. If the battery is 12.5 = 85% charged 12.4 = 65% 12.3 = 50% 12.2 = 35% 12.1 = drained Is this true? I read conflicting answers all over the internet. Reason I ask is I just bought a battery from Advance Auto parts about a month ago and noticed it has been slightly slower cranking over the first start of the day. So I checked it with my meter and it reads 12.4 - 12.5 The truck starts right up no problem after I ran the truck and shut it off during the day. So to me it sounds like the battery is not holding a charge overnight. I went back to autozone and they used a machine that puts a load on the system and prints out a receipt that says it's good. The battery is rated at 775 CCAs but on the test came out 830 CCAs and 12.9volts. The idiot who did the test told me "well the battery is at 12.9 volts" I said that's because I drove the truck here and the alternator charged it up its a surface charge. He says something nooo Anyway these guys know just enough to be dangerous. Those machines don't tell the voltage or how charged the battery is. Sure the machine will say good if it has enough power to do the load test even if it's drained some. So is it true I should have a 12.6V reading on a fully charged battery anything less it needs to be charged? And it shouldn't dip under 12.6 in less then 24 hours?
more beginner questions if you don't mind. WHen it's at 12.1 or lower where it's drained, can you still charge it back up to 100% heatthy state? or battery is gone?

when you start up the car and the voltage is under 13.8..that means alternator is bad? and during start up when voltage drop below 10v does that mean battery is going? EXACTLY what voltages should you be buying up a new battery?

07-20-2016, 12:37 AM
 483 posts, read 353,010 times Reputation: 120
I check my battery voltage and it's 12.84...why so high? I turned to accessories and turn on headlight for 3 minutes then checked it.

battery is 2.5 years old, 13.5k miles.

07-22-2016, 07:59 PM
 1,964 posts, read 2,381,785 times Reputation: 1884
Quote:
 Originally Posted by LVguy more beginner questions if you don't mind. WHen it's at 12.1 or lower where it's drained, can you still charge it back up to 100% heatthy state? or battery is gone?
You may want to review some of the other posts in the thread. The voltage readout alone is insufficient to determine whether the battery is still good. You may have good voltage but not generate enough current under load. You will also need to perform a load test. Remove the battery from the vehicle and take it to an auto parts store that will perform this test for you.

07-22-2016, 08:22 PM
 2,746 posts, read 3,421,309 times Reputation: 4253
Quote:
 Originally Posted by LVguy I check my battery voltage and it's 12.84...why so high? I turned to accessories and turn on headlight for 3 minutes then checked it. battery is 2.5 years old, 13.5k miles.
That's just a "surface" charge. It will read high after you drove the vehicle or started it. Check the voltage in the morning it will be lower no higher then 12.6 for sure.

10-25-2016, 07:48 PM
 2 posts, read 8,706 times Reputation: 10
The voltage meter in my 04 toyota says 16-17 on a 0-18 gauge... The needle staying there and doesn't change....is this high and a problem..

10-25-2016, 07:49 PM
 2 posts, read 8,706 times Reputation: 10
So what should I do I in the am it is still at 16-17

10-25-2016, 08:02 PM
 2,746 posts, read 3,421,309 times Reputation: 4253
Quote:
 Originally Posted by Southern Shon The voltage meter in my 04 toyota says 16-17 on a 0-18 gauge... The needle staying there and doesn't change....is this high and a problem..
yes something is wrong there a running vehicle should have a voltage between 13-14 volts. Take it to advanceauto parts or autozone they do free battery and alternator checks.

10-26-2016, 12:09 AM
 Location: Denver 3,138 posts, read 6,901,436 times Reputation: 2907
Quote:
I find it interesting that in 4 hours you took 120 amps from the battery it pretty much killed it.

10-26-2016, 12:11 AM
 Location: Texas 5,586 posts, read 11,831,318 times Reputation: 10545
It will depend on the vehicle as to what you'll get. Ford will usually charge more than other makes. My F150 with a 150 amp alternator will charge at max voltage of 14.2 volts. The battery after sitting over night will read 13.7-13.8 volts. My brothers Tacoma charges at 13.8 volts and at rest after 8 hours will be at 13.1-13.2 volts even on the same battery from my truck. My sisters Jeep Laredo charges at 13.2 and the battery at rest will be 12.8 prox. None are over charged and none are under charged. My battery has never needed any water and neither has bros or sister. My previous F150 was the same as far as voltage and over 100,000 miles never needed any battery service at 14.2 volts. My Bronco runs the same voltages and the battery in it is now 9 years old and starts the truck just fine. Bro on the other hand can't seem to make a battery last over 2 years regardless of brand or cost. Sister doesn't seem to have battery issues at all.

10-10-2017, 04:59 AM
 6 posts, read 16,787 times Reputation: 11
its copied from the NORTHERN ARIZONA WIND & SUN, it's not my work. I used this info when researching solar panels and batteries for off-grid: https://www.solar-electric.com/learn...ttery-faq.html

Quote:
 Originally Posted by wankel7 I find it interesting that in 4 hours you took 120 amps from the battery it pretty much killed it.
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