[Aragorn30d]

Did it sound like it was cranking over slowly?

If its winding over nice and quick its not a battery issue.

[vladmury]

it was cranking normally, i also remember on my older cars when battery was dead it was cranking slowly and dashboard lights were reseting, not the case here. Radio, mirrors, steering wheel lock, climate control all start ok.

[corsotx10]

Have you gotten the chance to check your alternator ?

[MX535]

Last year I replaced the battery on my 08 328xi because it had a hard time starting and wouldn't start when it got cold out. It was the original battery so it was due. Still did not start strong, you can tell its having a hard time turning it over. Measuring voltage today it's at 11.3-11.5 when car is off, drops to about 9v when starting and while running is 14.8-15.1 volts. Seems alternator is doing its job 11.5 seems low when the car is off but doesn't seem that bad. Any suggestions?

[Aragorn30d]

Measuring the Voltage of a battery in circuit doesnt always tell you that much.

The voltage of a 12v battery, when disconnected, can give a fairly good idea of its charge state. However when connected to your car, with the various modules and things in the car all drawing power from it, the voltage will dip down. As you've no idea what load the car is placing on the battery, the 11.5V reading is difficult to put into context.

If its charging properly but still not starting well, then check all the electrical connections in the starter circuit. This includes the big starter cable that runs up the car, earth terminations at the battery itself and the ground connection between the engine block and chassis. Could also be the starter itself has a partially shorted winding.

[SoZoX]

I looked at the hidden menu and I got a shocking surprise. When off around 11.9 but when on around 12.2-5 while driving. If pushing it and then just letting off (coasting) the voltage creeps to 13.9-14 as soon as I step on the gas 12.5. I noticed when parked I just have to put it in reverse and back to park the voltage gets up to 14.... every time. Step on gas 12.... WTF???? I got no codes battery is original I think car is from 2010.

[Leah1]

That normal mate mine does the same, it's part of the efficient dynamic brake regeneration uses the cars energy when braking or coasting.
And when you need the accelerate it cuts the alternator so less drag

[five50]

Hi All

Dont do a lot of miles in my E92 M3 and have the usual low battery level warnings. The battery was replaced by BMW 2.5 yrs ago when I got the car.

Have hooked up a 2.4watt solar panel to the car (current of 138 milli amps) and have left it on for a few days.

Yesterday evening after driving the car I had checked the voltage (£9.99 multimeter bought online) and it showed 12.18v (not bad).

I left the solar panel connected to the car today. It is generating electricity even in cloudy conditions (tested it with the multimeter). Disconnected the solar panel tonight and tested the battery voltage again. It showed a lower voltage of 11.9v. Not great.

I then did around 4-5 miles around town with 3 stops and checked the voltage again. It showed 12.38v which is a good reading.

However, am not sure why running the car would increase the voltage reading from 11.98v to 12.38v, unless either:

a. my cheap multimeter gives somewhat random results (but if I take a number of readings consecutively, they all read the same)
b. the battery somehow 'resets' itself once driven
c. something else is happening

Am assuming that the alternator wouldn't have the opportunity to put much juice into the battery on a short journey with lights and stereo on.

Any thoughts??

[F1HHR]

Guys my car alarm keeps going off at random times, I checked my battery in the morning after being parked all night and it was reading 11.8... I also then charged it for an hour or 2 but eventually started dropping voltage again and alarm kicked in. Do you think my battery is causing the alarm to go off?? Cheers

[flaviu918]

I just bought a new battery, its a 84ah 760a and it has 12.7v with engine off, but when i start the car it charges at 14.9v...isnt that to high? I registered the new battery as an 80Ah since i had only 2 options (80 or 90).

[Arch Stanton]

sounds blob on to me flaviu

[therealdb1]

Originally Posted by flaviu918

when i start the car it charges at 14.9v...isnt that to high?

Depends where you are measuring the voltage. If it is directly on the battery terminals that's around what you would expect to see.

[ryanmn]

Originally Posted by makkan00

I think it also depends on your battery Ah and alternator.

Mine is 14.1-14.3 max when car is running.
And 12-12.4 when car is off.

Hi Makkan00, my car battery before start tested with multimeter was 13.5 and when i tested on my instument cluster it was 12.2V.when i start the car jump down to 11.5-11.7 than it graduallly went up to 13.7-13.8 is that normal? there's guy told me that my battery is about to be depleted but i just replace the battery 3 days ago? any ideas? or is it normal?

[ryanmn]

my car before start i check the battery with multimeter and it stated that 13.5V but when i went and check on my instrument cluster it show 12.2V-12.3V than when i start crankinng it jump down to 11.6V than gradually go back up to 13.7-13.9V. is that normal?

[TinyAshes]

Soo, My 2006 E90 says 12.4v when sitting, and when I press Start, it goes to 10v, but jumps back up to 12.4v at idle. If i'm not getting the 13v/14v that you guys are saying it should be, then do I maybe have an alternator problem?

I started checking voltage because my shifting jerked around 4-5 gear, then the car goes into Limp Mode. I bought it 3 weeks ago, and always noticed that just before I come to a complete stop, the car jolts forward as if I'm getting slightly rear-ended or something. Its not violent, but its definitely noticeable. Reading around on here made me curious if I have a voltage issue causing this mess.
Indicator Light: Yellow Gear with Exclamation Point
Code: CCID:254

Thoughts?

[Pantrox]

Hi TinyAshes, it looks you are having the same problem as I'm dealing with.

Doing some laps in the nordschleife yesterday, the car went crazy, all kind of lights glowing in the cluster and battery sign.

With the -in dash voltimeter- I checked doing normal driving voltages around 13.8-9, sometimes fluctuating to 13.1 or so. Eventually, 12v and battery icon again.

I will try replacing the alternator completely just because it cost the same to put a refurbished one than changing the voltage regulator only (and there are so many options!!!).


Regards,

Ivan