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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Battery Voltage?



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      01-21-2013, 02:59 PM   #1
mistryn
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Battery Voltage?

What appears to be the norm for the battery voltage when the car is off and on?

I had a look through the hidden menu -

while the car was off it was around 12/12.1v
while the car was on it was around 14.7/14.8v

does the above seem the norm?
I think I am still on the original battery (4 years), not had any warning lights come up.
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      01-21-2013, 03:30 PM   #2
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Absolutely spot on with both sets of figures.
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      01-21-2013, 03:52 PM   #3
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how do you get this on the hidden menu? I've got idrive/nav pro if that makes a difference
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      01-21-2013, 04:33 PM   #4
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Thanks Dr Dave

Arch -

Put key into the slot
press and hold down the odometer reset button until you see warning triangle, keep it pressed down and will see some numbers/german language
let go and then press the button 19 times and then it will say lock on
then press the odometer button x amount times - this is your last 5 digits of the vin added together - i,e, AB12345 = 15 ==== press 15 times then it will say lock off

yuo are now in the hiddden menu
press it 7 times and you can view you coolant temp
press it 9 times you have battery voltage

if you press and hold down too long you will go into sub menu for each section, to come out just a short press

if you remove key then you have to re start all again
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      01-21-2013, 04:35 PM   #5
mistryn
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actually heres the vid how to do it
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      01-22-2013, 07:18 AM   #6
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Quote:
Originally Posted by mistryn View Post
What appears to be the norm for the battery voltage when the car is off and on?

I had a look through the hidden menu -

while the car was off it was around 12/12.1v
while the car was on it was around 14.7/14.8v

does the above seem the norm?
I think I am still on the original battery (4 years), not had any warning lights come up.

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.
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      01-22-2013, 08:23 AM   #7
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I will check the ah on the battery, how can tell ah on alt?
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      01-22-2013, 06:29 PM   #8
Dr Dave
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Voltage is unaffected by alternator output and battery capacity.

Your figures are perfect, don't worry.
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      01-23-2013, 07:51 AM   #9
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Think this way.

A car lead-acid battery is made up of six 2volt cells in series making 12 volts (all wet lead acid cells are 2 volts)

So it will be 12v, or just above, when not charging (6x2v = 12).

Lead acid cells need to be pushed above 2.25V to charge, so 6 x 2.25 = 13.5V

So it must be over 13.5 volts when running or else it won't charge properly.

Engine running volts shows the alternator is doing its job, but engine-off no-load voltage is not a very good indicator of battery condition, you need current/load to see how the volts drop to see if the battery is shagged.
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      01-23-2013, 08:30 AM   #10
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Quote:
Originally Posted by doughboy View Post
Engine running volts shows the alternator is doing its job, but engine-off no-load voltage is not a very good indicator of battery condition, you need current/load to see how the volts drop to see if the battery is shagged.
Totally agree but you can tell from the off-load voltage if a cell has gone short (plate-fuse) because the battery will only show 10v. However, I'm showing my age as I doubt that happens any more with gel-filled "wet" cells.
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      01-23-2013, 01:23 PM   #11
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Thanks guys interesting read but a little too complexed for my head
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      02-18-2013, 03:32 PM   #12
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Hey guys, my battery shows 9.7V when the engine is off. The engine wouldn't start without a jumper. The car - 2008 BMW 328i.

Can I somehow save/recharge/"have a 3-hour-drive on a highway" to reanimate my battery?
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      02-18-2013, 03:54 PM   #13
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You can always give it ago by taking it for a long drive...
Remeber cold can play havoc on batterys and if they are weak the cold will detrioate them more quicker.

How old is your battery?
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      02-18-2013, 06:01 PM   #14
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Quote:
Originally Posted by mistryn View Post
You can always give it ago by taking it for a long drive...
Remeber cold can play havoc on batterys and if they are weak the cold will detrioate them more quicker.

How old is your battery?
The battery is original, hasn't been replaced since 2008.

P.s. It shows 14.3-14.5V while I am driving.

Last edited by amtex; 02-20-2013 at 04:45 PM.
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      05-30-2013, 02:31 AM   #15
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can the alternator be a cause for a Transmission-limp and DCS fault?
I have these lights showing on my dash.

After the car was restarted all seems ok but I'm sure the problem will occur again.

Does low voltage errors mean there is a fault with the battery?
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      05-30-2013, 02:37 AM   #16
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sometimes low voltage/signs of battery dying can throw up various lights on the dash like the TC/transmission etc so may possibly be that
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      05-30-2013, 02:54 AM   #17
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I had the car checked out buy a dealer and they said it is an 80% chance that it could be the alternator.
They did not want to replace this as they cannot be 100% sure. I have to now wait till the problem occurs and then try and take it back to them before I restart the engine (which could be difficult)
Bit disappointed there is no log or a fault code that can give you an accurate diagnostics of the problem.

Reading the forums it seems there are a number of reasons for these ‘lights’ showing – this does not give me any confidence when driving the car.
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      11-17-2013, 09:56 AM   #18
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Am I in any sort of trouble here ? My 07 E93 Battery voltage is:

11.7V/11.6V when checked in the morning after leaving it parked overnight.

14.8v/14.9V when Driving

Something I have realised is, the Battery quickly loses charge as soon I shut down the engine. It drops to 13.1V then rapidly down to 12.5V and maybe drops further but I kinda just turn it off after it hits 12.5V. Its obvious it drops further as it hits 11V overnight.

All Comfort Access features (Keyless Start and Entry) do not work but apart from that, the Fobs Start, Open and Lock the car as normal.

Do I need to book it in at the dealer ? Is there a way INPA can scan CA and Battery ?

Its winter soon and I'm worried it might fail to start if Temperatures go sub zero.

Any advice will be much appreciated.
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      01-23-2014, 05:30 PM   #19
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Hi,
Today i started the car after 2 days of it being idle & the welcome lights refused to come on, i toke it for a nice 60-70 kms drive & after that parked the car & checked the Battery voltage on the Hidden menu. When the engine is not running the battery voltage was fluctuating between 11.6-11.9V When i started the car the Voltage of the battery went to 14.5V and then when i switched off the engine the voltage dropped to 11.8-11.9v in few minutes so i guess my battery has gone? doesn't seem to hold charge so i don't think even a battery charger will help, inputs would be great.

Thanks..
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      02-09-2014, 09:25 PM   #20
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I also have similar voltages (a little low actually, checked by voltmeter). However, my understanding is that it should be around 12.75 when fully charged... shouldn't it???
Thanks.
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      02-10-2014, 05:59 AM   #21
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Quote:
Originally Posted by umermariner View Post
I also have similar voltages (a little low actually, checked by voltmeter). However, my understanding is that it should be around 12.75 when fully charged... shouldn't it???
Thanks.
Normal lead acid battery is 2.1 volt per cell, 6 cells = 12.6 volts.
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      02-10-2014, 08:13 AM   #22
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I had a new O.E battery fitted under warranty at the main dealers. I do not do a lot of mileage so I bought a digital charger to keep the battery topped up because I like the stop/start system to keep working. I have noticed the battery condition before charging reads 12.1v to 12.3. The charger puts in 14.7v. and then clicks off. The reading then drops to 13.7 immediately and then creeps down to 12.3v. again.
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