[x5mad]

Car is a 328, Nov 2013 build with approx 13k.

I charged battery overnight and measured voltage both pre and post. Voltage was 12.5V and did not change after 12 hours of charging.

I have a loaner 125 same build date with approx 4k. Voltage reads 13.0V

Anything I should be concerned about?

[Labeef]

No, seems about right. Why are you worried about voltage? Batteries last about 4-5yrs on average.

[x5mad]

Originally Posted by Labeef

No, seems about right. Why are you worried about voltage? Batteries last about 4-5yrs on average.

Erm... Did you not read the whole post?

I know the voltage is within spec but the fact that after 12 hours of charging the voltage did not go up is what I am asking.

I charged my wife's golf and the voltage went up from 12.4 to 13.0

[x5mad]

One of the signs of impending failure is a battery which will not charge.

[CLittle]

I don't know much about car batteries but 12.5 V sounds right.

With all the voodoo glass mat battery and battery condition sensing technologies, I would personally avoid charging the battery if there is nothing wrong with it.

[x5mad]

Originally Posted by CLittle

I don't know much about car batteries but 12.5 V sounds right.

With all the voodoo glass mat battery and battery condition sensing technologies, I would personally avoid charging the battery if there is nothing wrong with it.

Wow is nobody understanding my post?

I am not concerned about it being 12.5v as I already said it's within limits.

F30 uses AGM battery, my old x5 had AGM and this 125 loaner has AGM battery.

Apart from my car they ALL charged to 13V.

[stormlv]

Originally Posted by x5mad

Wow is nobody understanding my post?

I am not concerned about it being 12.5v as I already said it's within limits.

F30 uses AGM battery, my old x5 had AGM and this 125 loaner has AGM battery.

Apart from my car they ALL charged to 13V.

Sorry, couldn't help it

Anyway, it's indeed odd that it didn't charge it at all.

BTW, why did you have to recharge the battery on a 8 month car? I left mine two weeks in the garage and it was OK...

[x5mad]

Finally! Lol

It was only cos I was coding car for a while so decided to let it charge overnight

[stormlv]

Originally Posted by x5mad

Finally! Lol

It was only cos I was coding car for a while so decided to let it charge overnight

This article may be interesting: http://www.scubaengineer.com/documen...ing_graphs.pdf

Page 3 (68) shows a nice plot of the state of charge vs voltage on a discharging battery.
As you can see, differences between 50% charge and 100% charge in terms of voltage are pretty small.
Maybe temperature differences account for the same measured voltage on the battery (beginning of night vs morning), even though the battery may have well charged?

I wouldn't worry about it unless you find it flat after leaving it a short time...

[Austinformedude]

Voltage state has little to due with actual CHARGE state. There are multiple cells in the battery (usually 4 3V cells) that add up to 12v. You need to measure the cranking amps. Available amperage (current) is what you are looking for NOT voltage to determine condition. I wouldn't be worried unless you were seeing less that 12V because that would indicate a bad cell. Also AGM batteries that most newer BMWs have come with a monitor system, so you should not be charging it yourself while it is installed. You can damage the battery, monitor, or even the car electronics.

[stormlv]

Originally Posted by Austinformedude

Voltage state has little to due with actual CHARGE state. There are multiple cells in the battery (usually 4 3V cells) that add up to 12v. You need to measure the cranking amps. Available amperage (current) is what you are looking for NOT voltage to determine condition.....

Actually for lead-acid batteries, measuring open-circuit voltages to determine state of charge works reasonably well. This, doesn't hold well for other types of batteries, like LiIon.

Originally Posted by Austinformedude

... Also AGM batteries that most newer BMWs have come with a monitor system, so you should not be charging it yourself while it is installed. You can damage the battery, monitor, or even the car electronics.

Interesting, I didn't know that

[rking117]

anythign above 12V is ok, the better read out may be up to 14 V though. I would say if you are not having lacg when cranking then you are ok.

[x5mad]

Originally Posted by Austinformedude

Voltage state has little to due with actual CHARGE state. There are multiple cells in the battery (usually 4 3V cells) that add up to 12v. You need to measure the cranking amps. Available amperage (current) is what you are looking for NOT voltage to determine condition. I wouldn't be worried unless you were seeing less that 12V because that would indicate a bad cell. Also AGM batteries that most newer BMWs have come with a monitor system, so you should not be charging it yourself while it is installed. You can damage the battery, monitor, or even the car electronics.

I have a CTEK with option to charge AGM batteries.

I should not be charging still?

[Stoofpilot]

Could be a bad IBS cable. The sensor only let's the alternator charge up to the last reading. I just had mine replaced in my 2013. BMW has a new cable.

[Weaselboy]

Originally Posted by Austinformedude

Also AGM batteries that most newer BMWs have come with a monitor system, so you should not be charging it yourself while it is installed. You can damage the battery, monitor, or even the car electronics.

I don't know where you go that from, but the owners manual even tells you to charge if the car will be unused for a long period of time and BMW sells their own branded chargers on their web site.



I agree one should not throw their WalMart 80AMP charger on there, but no harm if using the correct charger.

OP> I have a 2014 335i and have had a Deltran battery tender running on the under hood connections for about two weeks (car not driven) and I just disconnected the charger and took a read from the posts and get 13.03 volts. I think you are in the normal range and would not be too concerned about it.

[iwinit]

To the OP, if you have a high quality charger, the voltage should be at least 13V after charging it for 12 hours, no matter what charge mode. Something is definitely not right. I charge the batteries of all my vehicles once every another month to keep them in optimal condition. My F10's battery is usually 50-60% charged after two months' use and voltage is below 12.6V. After charging it full, voltage becomes 13.4V. According to the manual of my battery charger, when the voltage of a car battery is below 12.7V, it should be charged. I think it is a good way to prevent/delay sulfurization and prolong the battery life.

[x5mad]

Looks like someone is on the same wavelength. I just think it common sense that if you charge a battery it should go up in voltage if not already at maximum. Same as if you were charging any rechargeable battery.

Well, my current SA is an absolute idiot. Argued with me that the car does not have an AGM battery. End of day I knew they were just gonna say it's within tolerance.

I have a chart which gives you an estimation of SOC based on ambient temperature and voltage. 12.5 is only just over 50%.

I call bs, but will just have to keep an eye on it.

[Labeef]

Originally Posted by x5mad

Looks like someone is on the same wavelength. I just think it common sense that if you charge a battery it should go up in voltage if not already at maximum. Same as if you were charging any rechargeable battery.

Well, my current SA is an absolute idiot. Argued with me that the car does not have an AGM battery. End of day I knew they were just gonna say it's within tolerance.

I have a chart which gives you an estimation of SOC based on ambient temperature and voltage. 12.5 is only just over 50%.

I call bs, but will just have to keep an eye on it.

I understood your question. Just because you charge your battery for 12hrs means that it should jump up to 13v. Read the rest of the posts, they are pretty knowledgeable.

[Amused]

99.9% of car batteries consist of 6 cells with each being 2.11 volts each for a total of 12.66 volts. You have nothing to be concerned about. Most cars altenators when running will put of approx. 14.4 volts to charge the battery and to overcome that batteries resistance.

[x5mad]

Originally Posted by Labeef

I understood your question. Just because you charge your battery for 12hrs means that it should jump up to 13v. Read the rest of the posts, they are pretty knowledgeable.

Yes indeed they are all useful posts and I never argued with anyone about being wrong. In fact I agreed.

And I didn't say that i expected it to go up to 13v I only gave examples of other cars.

My concern was that the voltage did not go up at all.

Perhaps I asked it all wrong but let's say you start off with a battery with 12.0V even. That's still within tolerance. But now say you charge that battery for 12 hours overnight. Would you not expect the voltage to go up?

This happened on my e46 and within a few weeks it was dead.

Like I said will monitor and report back if anything comes out of it. Hopefully all good.

[Austinformedude]

http://www.mpoweruk.com/soc.htm

This article is probably the best out there. Much more detailed that can get into here.

[Amused]

Originally Posted by x5mad

Yes indeed they are all useful posts and I never argued with anyone about being wrong. In fact I agreed.

And I didn't say that i expected it to go up to 13v I only gave examples of other cars.

My concern was that the voltage did not go up at all.

Perhaps I asked it all wrong but let's say you start off with a battery with 12.0V even. That's still within tolerance. But now say you charge that battery for 12 hours overnight. Would you not expect the voltage to go up?

This happened on my e46 and within a few weeks it was dead.

Like I said will monitor and report back if anything comes out of it. Hopefully all good.

When you charge a battery you are charging amperage, not voltage. If you are concerned with how your battery is functioning, find a place that can perform a load test on the battery.