Healthy battery voltage
- Thread starter Henrick
- Start date
bluesmoker
Veteran Member
12.6 at rest
http://en.wikipedia.org/wiki/Automotive_battery
about 14.4 while the car is running
http://en.wikipedia.org/wiki/Automotive_battery#Charge_and_discharge
http://en.wikipedia.org/wiki/Automotive_battery
about 14.4 while the car is running
http://en.wikipedia.org/wiki/Automotive_battery#Charge_and_discharge
Alchemist
Veteran Member
A good battery should have about 12.3 to 12.7 V open circuit after sitting for some time since running. When running, the voltage should be no less than 13.8, but 14.4 is preferred. Unless there is a heavy load, it shouldn't vary much from idle to 2000 rpm.
Paul
Paul
cleaver
Veteran Member
I have 12.6v with the ignition off, and 13.8v while driving. (13.7v-14.0). I used to have 14.2v steady, but then I had to replace my alternator. Replaced it with a Bosch (correct part) and now I have 13.8 steady.
cleaver
Veteran Member
revving your engine (varying rpm's) should have very little, if any, effect on your charge. I would check your alternator if you are getting fluctuating (wildly) numbers.
whitedog
Veteran Member
The guy is in Ireland. What do those voltages convert to in Metric?
Thanks for replies. I measured (with multimeter) voltage at my battery and got 12.6 V after ~2 minutes have passed after a shutdown. I started it back and it showed 13.8 V at idle and 14.1 V at 2000 RPM. I think this sounds more or less normal, right?
whitedog
Veteran Member
I'm glad someone got my joke.12600 mV idle
13800 - 14400 mV running
Yes. It certainly sounds normal. Why are you asking? Is this just a check-up or are there problems you are troubleshooting?
I left my car for an underbody, body and interior wash. They also had to fix some dents and scratches on the body. So they were working on the car all day. The doors and both, trunk and hood were opened all day long. Finally they called me to say the car's ready. It took me 30 minutes to arrive. When I arrived I found my car idling. I asked why it was that and the manager said there was a problem - the battery got discharged (dead) and they couldn't start the car. So they charged it a little bit and started the car. They must have charged it for ~15 minutes, I think, because when I arrived and found my car the clock (as well as trip odometer, steering wheel and window adaptation) was reset and it showed something like 0:14.
I payed for the job and left. Today the car did start in the morning. I'm worried the alternator might not charge enough the battery so I'm afraid I might have starting problems when temperatures drop and the ECU will use Glow Plugs.
I payed for the job and left. Today the car did start in the morning. I'm worried the alternator might not charge enough the battery so I'm afraid I might have starting problems when temperatures drop and the ECU will use Glow Plugs.
cleaver
Veteran Member
It almost sound like something is draining the battery when it is turned off.
It could still be a faulty voltage regulator on the alternator, but it could be something else draining the battery.
Anything installed lately or repaired?
It could still be a faulty voltage regulator on the alternator, but it could be something else draining the battery.
Anything installed lately or repaired?
mohawk69
Veteran Member
I wouldn't worry about it. The doors were open and I'm sure the music was blaring all day. How old is the battery? If it's relatively new, it just needed a chance to recharge and should give you no problems.
No, it isn't draining the battery on regular basis. No electrical changes ever (no aftermarket stereo, amplifiers, etc.. Yeah, I know, I'm a boring person). I turned off the radio before leaving the car. I believe it's because the light inside the trunk don't time out (interior lights do time out but they probably were opening/closing doors frequently while cleaning. Interior lights drain 30 Watts at least).
Please don't start a flame. The battery is still original and it's actually 6 years from the date of manufacture. It started just perfect last winter every day. Hope it will work this winter too.
Please don't start a flame. The battery is still original and it's actually 6 years from the date of manufacture. It started just perfect last winter every day. Hope it will work this winter too.
mohawk69
Veteran Member
I'd be prepared to buy a battery this winter but I wouldn't until it started showing signs of failure. I think everything is working normally but that battery is near it's final days.
coalminer16
Top Post Dawg
Honestly a voltage test does very little to tell if a battery is good. But if it is off it can forsure tell you it is bad. A load test is better as it drains a bit out of the battery and sees if it can handle the load for a period of time. The cheaper testers are normally like a vented toaster oven but they work.
Ol'Rattler
Top Post Dawg
+1. As a battery ages, the capacity diminishes. About all a voltage test can confirm is that there are shorted cells or your alternator is not charging.
On the newer cars, the controller turns off the interior lights after about 10 minutes and the radio after an hour. If the battery couldn't handle that, it's about done. 6 years is about the limit for a battery, anyway.
Something you could try is to turn on the headlights (torches?) without the engine running for about 10 minutes and then try to start the car. A healthy, fully charged battery should start the car with no problem.
whitedog
Veteran Member
Another way to test the battery is to disable the fuel system, put the voltmeter on the battery and crank the engine over for 15 seconds and watch the voltage at the battery. It should stay above something like 9.5 volts then recover back to just about the open circuit voltage within a few seconds.
Is the controller supposed turn off the trunk light also (MkV)?
Ol'Rattler
Top Post Dawg
I don't know for sure. When I get back home I will leave a door and the trunk open and see what does happen.
I do know that if you pop the trunk and arm the alarm, the interior lights go out but the trunk light stays on till you close the trunk.
That's right, I've checked & confirmed that a few days after I bought the car. It also cuts off power to glove box light.
But I wonder if trunk does time out after not being closed...
Thanks for input. Can anyone confirm this is the same case with MkV too?