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



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      06-15-2012, 03:16 AM   #23
AlwynMike
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I would still expect 14.4 volts or so with the engine running, particularly after just starting the car, as the battery will be depleted. 12.4 volts after the car has been standing is OK. It's pointless measuring the voltage whilst on the CTEK, as this will just read the charger voltage. With it a 13 volts or so, this indicates that the battery will be pretty fully charged.
Leaving the car with either the ignition on or with ignition off, but radio/iDrive on for even a relatively short period will take a lot out of your battery. These cars have such a mass of electronics that need to be fed, even when the car is seemingly switched off, it can quickly flatten an average battery.
My 530d, at 3 years old, would throw up a low battery alarm after an hour ignition off, but iDrive & radio on.
Certainly, if the car may have the original battery, then change it - you'll probably have to do that this winter anyway!

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      06-15-2012, 03:50 AM   #24
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12.3v is Ok for the standing battery voltage without alternator and seems to show it is OK (with no load anyway). A car battery is made of 6 x 2V lead acid cells, so 12v is the 'nominal voltage', 12.3v is OK, if a little down from say ideal 12.6v-ish fully charged.

With engine running as said it should be nearer 14v alternator output, so it still looks like an alternator issue IMO.

Don't measure with CTEK on, that's meaningless as its just the CTEK voltage you are seeing.

You need to see how quickly the battery voltage drops over say 10 minutes with radio / idrive on / headlights on etc but engine OFF. If the battery is defective or not well charged (say a faulty cell, or high resistance internally) then the battery voltage will drop quite a bit in 10 minutes with accessories on.

Give that a go.
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      06-15-2012, 09:03 AM   #25
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The question I don't get is that when the charger displayed fully charged it was still delivering 13volt plus so is it not charged properly. When I unplugged it, it displayed 12.4volt and this morning I checked again before going out and it was around 12.2volt.
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      06-15-2012, 09:54 AM   #26
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Quote:
Originally Posted by sylonien View Post
The question I don't get is that when the charger displayed fully charged it was still delivering 13volt plus so is it not charged properly. When I unplugged it, it displayed 12.4volt and this morning I checked again before going out and it was around 12.2volt.
Just tried the voltage on my car, 12.3v battery reading static. Started car with all load as possible turned off 14.3v charge and this is after a number of short trip journeys. I have a Ctek XS7000 and will cycle back to charge if there is a problem with the battery not holding its charge but that would be indicated on the charger as it would start the charge cycle again.


"You need to see how quickly the battery voltage drops over say 10 minutes with radio / idrive on / headlights on etc but engine OFF. If the battery is defective or not well charged (say a faulty cell, or high resistance internally) then the battery voltage will drop quite a bit in 10 minutes with accessories on".

Just read the manual for my charger and it states:-
Pulse Maintenance charge: The state of charge is between 95% and 100%. A pulse at 5 A is sent out if the voltage drops. This gives mini- mum water loss and maximum life. The charger could be connected for years without problems. The charger measures the voltage every 10 minutes to decide whether a new pulse should come. This means that these pulses can’t come more often than every 10 minutes.
If the battery is charged and/or the battery's terminal voltage drops below 12.7 V (Mode 14.4 V) or 12.9 V (Mode 14.7 V), the charger starts a charge pulse of 5A until the terminal voltage has reached the set level, 14.4 V or 14.7 V. The charge pulse is then interrupted and the cycle is repeated as long as the charger is in pulse maintenance phase. Pulse maintenance phase is indicated by lamp 4. If the terminal voltage drops below 12.1 V, the charger automatically reverts to the beginning of the charging curve.

The above will explain your reading of 13v when you think the charge is complete.

Last edited by greatbm; 06-15-2012 at 10:53 AM.
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      06-22-2012, 04:24 AM   #27
sylonien
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Thanks for the info, very helpful.

I will take a reading again today. Just drove the car none stop from Manchester to Bath the day before (180miles / 3:30hours). Surely that would charge it significantly?

It's been left standing for day yesterday. Will see what the voltage is like after leaving it for a day on its own.

Have you changed the battery before and what size is your battery? Mine is 70Ah.
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      06-25-2012, 10:20 PM   #28
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Anyone ordered from http://www.carbatteriesonline.co.uk before?
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      08-08-2012, 08:00 AM   #29
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Just some photo update, had this done before I went to Germany.
Took it to a specialist and coded it via autologic. Rang different places, some say you needed to and some don't. Should of cost 30 ish but needed to update some other software, there were 20+ things to be updated apparently but just did the few that needed before autologic let is retrofit a higher capacity battery. Something to do with the seatbelt, door control software etc bizarrely.

Anyway, the standard battery was a 70Ah but I fitted it with a 85Ah. But it program only let me choose 70, 80, 90. So went for 80Ah instead. don't want it to overcharge or something other.

At first it didn't look like it would fit a larger battery in the space, but it did at the end and apparently that clamp thing on top of the battery was a bit loose cause it's not OEM. But it's only a tiny tiny bit of movement. Nothing to worry about.

So, been and back from Germany now after some 1000+ miles of driving. Car started fine with no error messages etc. So far so good and saved quite a bit and larger Ah compared to OEM. And surely BOSCH battery can't be that bad?! German too!


Battery arrived.


New battery - yaay!


Reading straight out of box.


Left it on CTEK charger before fitted and the reading after unplugging.


Car battery after charging and unplugging (old battery).
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