Battery Voltage?

umermariner · 02-10-2014, 08:57 AM

I tested on another new battery (ford focus) as well, and the voltage next morning was 12.16. Only on the motorcycle, the voltage was 12.5.
Seems like there is a disconnect. Either the batteries are not good, or the info we got does not apply to them??

umermariner · 02-10-2014, 09:39 AM

Also, anyone tried a PulseTech charger on BMWs? Its the charger pushing pulses of current to desulfate the battery.

doughboy · 02-10-2014, 09:54 AM

I work in test & measurement, beware fussing about 0.1 of a volt here and there.

Even a quality, calibrated multimeter costing several hundred quid will only be accurate to +/-1%.

So that is +/-0.12v accuracy AT BEST at 12v

A cheap crap charger voltmeter is probably 5% or 10% at best, i.e. 0.6v or 1.2v at 12v.

Keep it simple, if the battery is above 12v when the car isn't running, then its probably OK. If it drops with no load in a few hours then its probably knackered or on its way.

If it jumps to 14+ when running then the alternator is doing its job ok.

Ideally yes 12.6 is nicely charged, but over 12 is fine.

F104 · 02-10-2014, 11:37 AM

Mistryn, I have ED. New battery installed one year ago, and saw exactly the same readings as you posted. Stop/start did mostly not work either. Only thing that has changed is my driving habit. I still do basically long distance only but car sits now in the garage for up to 2-4 days.

Two weeks ago I decided to hook up the bike's Optimate. Just make sure it does not go to red (desulfate) , as then it will send 22V into the battery, and AGM does not like more than 14.8V). It took more than two days (actually 60 hrs at least & it should charge at 2A), to get the green light to come on the optimate. Doesn't make sense, as that represents 120Amp-hr, and i have a 90 Amp-hr battery that was far from empty (well 11.9V)

And beyond me, start/stops work again. What's more important, I see now more realistic voltage readings on my OBD dispay. To be sure the OBD reads correctly, i had hooked up a Fluke too. The OBD does read correctly within 0.1V

So previously i saw 14.4-14.8V all the time. That's alternator voltage you are seeing, charging the battery. I now see 14V max, and only 14.8V when braking/decelerating (which is what it is supposed to do). What I don't understand yet is I've seen see voltage drop to 12V before it starts charging again. It should drop to only 12,5V or so, representing 80% State Of Charge.

I'll keep it on the charger & see if that improves things over time. But with engine off for hours/days I read now 12.3-12.4V, instead of 11.9-12.0.

Maybe two interesting links:
from BMW training
http://prodcds.bmwuniversity.com/lib...y%20Basics.pdf

and how it does looks at energy in out while driving (as indicated in above link)
http://www.altenergystocks.com/archi...ry_market.html

Soul_Glo · 02-10-2014, 11:49 AM

I use a multi-meter which also has an amp clamp in case I ever need it...

My resting voltage is 12.4v-12.8v
My operating voltage is 14.8v-15v

If I leave it for more than 3 days it is usually around 11.9v as I have a lot of after market security on the car.

I drive it for more than 1.5 hours every day 5 days a week. I stick it on the ctek mx.5.0 battery tender every other weekend... and it charges up in about 4 hours. It charges upwards from 80% and is never below that.

It is definitely worth investing in a c-tek on a side note!

Terryk · 02-10-2014, 02:25 PM

same situation with mine, drops at 11.8-11.9 when is switched off but when I drive the car it shows 14.1-14.4
I read these values for as far as I remember, meaning over two years now

umermariner · 02-10-2014, 03:08 PM

I just put a charger that desulfates as well on my battery. Even though, the battery was charged to 100% twice in the past week, this charger said its 25%. Lets see how it works, and if it can bring the voltage up/ close to 12.75 volts.

umermariner · 02-10-2014, 03:12 PM

Quote:

Originally Posted by Terryk

same situation with mine, drops at 11.8-11.9 when is switched off but when I drive the car it shows 14.1-14.4
I read these values for as far as I remember, meaning over two years now

How old is the battery? Do you remember seeing the same values when it was new?
Thanks.

Dan-danGT · 02-12-2014, 10:28 AM

I have a similar problem, if I sit with my ignition on for 10 minutes my e90 will have a flat battery! Now I have had it checked at bmw they say it's all ok charging fine and battery is good. Now to me that battery is far from good. If I start my car in the morning it's at 12.1v then when cold it's still at 12.5v when you bring up the revs slightly it will resume 14.8v. Bmw told me the car wi'll charge as and when needed well surly after a cold start it has to replenish that lose but it does not appear to.

Also they said my driving is not adequate, I do a minimum of 25 miles a day so that driving not adequate is crap. How ever this stupid active brake regeneration apparently turns off the alternator when I'm on 100% throttle to give me more power? Now thats all good but once it's warm I do drive pretty damn quick most places so it's hardly going to charge! Or am I missing someying?

Over Christmas I put the car on charge using a snap on battery charger, which immediately stated battery was sulphated and would take Upto 24hr before it could resume charging. Once I came back 2 days later it said bad battery.

So i used a different charger to charge it which worked and our midtronics battery tester passed it but it still went flat. I just think the battery is weak!

If I install a new battery and tell the car it has one is that it all done? Bmw told me they need a code of the top of the battery to register it? Surely that's for a different amp rating maybe? I don't have the bmw software so can't confirm this. If someone knows the answer that would be nice to know

umermariner · 02-12-2014, 11:47 AM

Did they actually performed load test on your battery and passed it? Seems to me that your battery is severely sulfated, and even though shows normal voltage, would fail under load.

insane79 · 02-12-2014, 01:25 PM

Quote:

Originally Posted by Dan-danGT

I have a similar problem, if I sit with my ignition on for 10 minutes my e90 will have a flat battery! Now I have had it checked at bmw they say it's all ok charging fine and battery is good. Now to me that battery is far from good. If I start my car in the morning it's at 12.1v then when cold it's still at 12.5v when you bring up the revs slightly it will resume 14.8v. Bmw told me the car wi'll charge as and when needed well surly after a cold start it has to replenish that lose but it does not appear to.

Also they said my driving is not adequate, I do a minimum of 25 miles a day so that driving not adequate is crap. How ever this stupid active brake regeneration apparently turns off the alternator when I'm on 100% throttle to give me more power? Now thats all good but once it's warm I do drive pretty damn quick most places so it's hardly going to charge! Or am I missing someying?

Over Christmas I put the car on charge using a snap on battery charger, which immediately stated battery was sulphated and would take Upto 24hr before it could resume charging. Once I came back 2 days later it said bad battery.

So i used a different charger to charge it which worked and our midtronics battery tester passed it but it still went flat. I just think the battery is weak!

If I install a new battery and tell the car it has one is that it all done? Bmw told me they need a code of the top of the battery to register it? Surely that's for a different amp rating maybe? I don't have the bmw software so can't confirm this. If someone knows the answer that would be nice to know

Whats your battery age? seems to me your battery is on its way out.

Dan-danGT · 02-12-2014, 02:14 PM

2008 it's as old as my car, bmw want £285 Inc for a battery robbing gits!,

insane79 · 02-12-2014, 02:21 PM

Quote:

Originally Posted by Dan-danGT

2008 it's as old as my car, bmw want £285 Inc for a battery robbing gits!,

i just got my battery replaced, mine was a 09 E90, your battery is on its last legs, better you change it then get stranded somewhere..

Dan-danGT · 02-12-2014, 03:15 PM

It's got auc warranty so I keep getting them out as and when, I have a problem coming up as it's going in for a remap soon and really could do without it dying during programming it could knacker the ecu! Will get one asap!

It's died 3 times, last time they was downloading my files from the dde! But took me ages to get it to jump start! It only does it when ignition is on for 10 minutes. Starts every time if I jump in and press start.

I will replace it but 285 is steep for a battery, I'm trying to find a varta with the same rating to sort all my problems lol

insane79 · 02-12-2014, 03:22 PM

Quote:

Originally Posted by Dan-danGT

It's got auc warranty so I keep getting them out as and when, I have a problem coming up as it's going in for a remap soon and really could do without it dying during programming it could knacker the ecu! Will get one asap!

It's died 3 times, last time they was downloading my files from the dde! But took me ages to get it to jump start! It only does it when ignition is on for 10 minutes. Starts every time if I jump in and press start.

I will replace it but 285 is steep for a battery, I'm trying to find a varta with the same rating to sort all my problems lol

your battery has lived its life, 4-6 years is the normal life span. get one if you fear of frying your ECU

Pennywise pound foolish eeh..

umermariner · 02-12-2014, 05:11 PM

Quote:

Originally Posted by insane79

your battery has lived its life, 4-6 years is the normal life span. get one if you fear of frying your ECU

Pennywise pound foolish eeh..

Fry ECU??? by dying battery? How?

Dan-danGT · 02-13-2014, 01:01 AM

Yeah I'm on it today! Does really oem give battery ratings?

RustyT · 08-13-2015, 04:32 PM

Hi

We have various warning lights coming up on our 2011 E91 320d. They don't stay on for long and it's mainly the ABS but definitely others. They only come on a couple of times a week and usually only for a second or two. We've also had an intermittent problem of the boot lock not activating when you shut the boot. We've only had the car a couple of months and it's been off and on.

I took it to a dealer and they diagnosed as an overcharging alternator and that a new alternator 'should sort out most of the problems' but would cost £1000!!!

Having read forums, the symptoms do often relate to alternator or voltage regulator issues. However, following tips on forums I have also accessed the hidden menu to find that the voltages are reading around 12.2 when off and 13.8v when idling and revving the engine lightly. From the posts above it suggests that the voltage is OK (or do I need to run it full pelt to make sure it's not overcharging?).

I'm now thinking that the dealer might just be going for a quick grand so I'm going to call them to probe them more on their voltage readings. Anyone know if it's likely to be anything else, I.e possible ABS sensor throwing other errors up to? also saw mention or another cable on the battery but can't remember the name but it was related to the charging.

Any thoughts on what others think it could be. And hether I'm right to thinking the overcharging diagnosis may be incorrect. I kind of thought this should be clear cut from all the diagnostics but I'm seeing different through my untrained eye.

Thanks in advance

Russell

Aragorn30d · 08-14-2015, 05:30 AM

You need a decent diagnostic scan on the car to see why its bringing on the lights. When lights come on, the ECU involved will log a fault code.

13.8v at idle does sound pretty normal to me. I would say maximum charge voltage for a 12v lead acid was around 14.4v, but these cars to seem to run higher than that for a short time to charge the battery quicker. If its exceeding 15v for any length of time then you risk damaging the battery.

kiel_dafo_kenyg_as · 08-15-2015, 04:25 AM

ABS codes can trigger a couple of other (unrelated) codes. Your alternator and battery is fine and your dealer is a douche. Do not go there again.

corsotx10 · 10-08-2015, 08:11 AM

My engine running battery is 13.5-7v according to in dash reading. Battery hasn't been changed before. Should I be worried? I do not have any symptoms yet.

vladmury · 01-01-2016, 04:11 PM

My car this morning did not start since last night all was good. It cranks normally but wont start, i checked the battery voltage was 12 v with engine off then droping at 11.9. When i press the start button, voltage drops to 8,7 V when cranking its normal?

After 3rd attempt and a lot of cranking it started, checked with Inpa no errors on engine module.

Should i buy a new battery?

02-10-2014, 08:57 AM	#23
umermariner New Member 0 Rep 14 Posts Drives: E60 Join Date: Jun 2012 Location: NJ iTrader: (0)	I tested on another new battery (ford focus) as well, and the voltage next morning was 12.16. Only on the motorcycle, the voltage was 12.5. Seems like there is a disconnect. Either the batteries are not good, or the info we got does not apply to them??
	Appreciate 0 Quote

02-10-2014, 09:39 AM	#24
umermariner New Member 0 Rep 14 Posts Drives: E60 Join Date: Jun 2012 Location: NJ iTrader: (0)	Also, anyone tried a PulseTech charger on BMWs? Its the charger pushing pulses of current to desulfate the battery.
	Appreciate 0 Quote

02-10-2014, 09:54 AM	#25
doughboy Major General 1545 Rep 8,970 Posts Drives: 2018 M2 Comp 6MT Join Date: Jan 2009 Location: UK iTrader: (2)	I work in test & measurement, beware fussing about 0.1 of a volt here and there. Even a quality, calibrated multimeter costing several hundred quid will only be accurate to +/-1%. So that is +/-0.12v accuracy AT BEST at 12v A cheap crap charger voltmeter is probably 5% or 10% at best, i.e. 0.6v or 1.2v at 12v. Keep it simple, if the battery is above 12v when the car isn't running, then its probably OK. If it drops with no load in a few hours then its probably knackered or on its way. If it jumps to 14+ when running then the alternator is doing its job ok. Ideally yes 12.6 is nicely charged, but over 12 is fine.
	Appreciate 0 Quote

02-10-2014, 11:37 AM	#26
F104 Captain 19 Rep 732 Posts Drives: E92 320D M-sport Join Date: Apr 2008 Location: belgium iTrader: (0)	Mistryn, I have ED. New battery installed one year ago, and saw exactly the same readings as you posted. Stop/start did mostly not work either. Only thing that has changed is my driving habit. I still do basically long distance only but car sits now in the garage for up to 2-4 days. Two weeks ago I decided to hook up the bike's Optimate. Just make sure it does not go to red (desulfate) , as then it will send 22V into the battery, and AGM does not like more than 14.8V). It took more than two days (actually 60 hrs at least & it should charge at 2A), to get the green light to come on the optimate. Doesn't make sense, as that represents 120Amp-hr, and i have a 90 Amp-hr battery that was far from empty (well 11.9V) And beyond me, start/stops work again. What's more important, I see now more realistic voltage readings on my OBD dispay. To be sure the OBD reads correctly, i had hooked up a Fluke too. The OBD does read correctly within 0.1V So previously i saw 14.4-14.8V all the time. That's alternator voltage you are seeing, charging the battery. I now see 14V max, and only 14.8V when braking/decelerating (which is what it is supposed to do). What I don't understand yet is I've seen see voltage drop to 12V before it starts charging again. It should drop to only 12,5V or so, representing 80% State Of Charge. I'll keep it on the charger & see if that improves things over time. But with engine off for hours/days I read now 12.3-12.4V, instead of 11.9-12.0. Maybe two interesting links: from BMW training http://prodcds.bmwuniversity.com/lib...y%20Basics.pdf and how it does looks at energy in out while driving (as indicated in above link) http://www.altenergystocks.com/archi...ry_market.html
	Appreciate 0 Quote

02-10-2014, 11:49 AM	#27
Soul_Glo Major General 13346 Rep 7,484 Posts Drives: G20 Join Date: May 2013 Location: Manhattan, NYC iTrader: (1)	I use a multi-meter which also has an amp clamp in case I ever need it... My resting voltage is 12.4v-12.8v My operating voltage is 14.8v-15v If I leave it for more than 3 days it is usually around 11.9v as I have a lot of after market security on the car. I drive it for more than 1.5 hours every day 5 days a week. I stick it on the ctek mx.5.0 battery tender every other weekend... and it charges up in about 4 hours. It charges upwards from 80% and is never below that. It is definitely worth investing in a c-tek on a side note!
	Appreciate 0 Quote

02-10-2014, 02:25 PM	#28
Terryk Second Lieutenant 26 Rep 231 Posts Drives: F30 mineral grey N47 ed Join Date: Jan 2013 Location: Hertfordshire, UK iTrader: (0)	same situation with mine, drops at 11.8-11.9 when is switched off but when I drive the car it shows 14.1-14.4 I read these values for as far as I remember, meaning over two years now __________________ F30 mineral grey N47 ed
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02-10-2014, 03:08 PM	#29
umermariner New Member 0 Rep 14 Posts Drives: E60 Join Date: Jun 2012 Location: NJ iTrader: (0)	I just put a charger that desulfates as well on my battery. Even though, the battery was charged to 100% twice in the past week, this charger said its 25%. Lets see how it works, and if it can bring the voltage up/ close to 12.75 volts.
	Appreciate 0 Quote

02-12-2014, 10:28 AM	#31
Dan-danGT Captain 33 Rep 650 Posts Drives: E90 330d M-Sport Join Date: Dec 2012 Location: Nottinghamshire iTrader: (0)	I have a similar problem, if I sit with my ignition on for 10 minutes my e90 will have a flat battery! Now I have had it checked at bmw they say it's all ok charging fine and battery is good. Now to me that battery is far from good. If I start my car in the morning it's at 12.1v then when cold it's still at 12.5v when you bring up the revs slightly it will resume 14.8v. Bmw told me the car wi'll charge as and when needed well surly after a cold start it has to replenish that lose but it does not appear to. Also they said my driving is not adequate, I do a minimum of 25 miles a day so that driving not adequate is crap. How ever this stupid active brake regeneration apparently turns off the alternator when I'm on 100% throttle to give me more power? Now thats all good but once it's warm I do drive pretty damn quick most places so it's hardly going to charge! Or am I missing someying? Over Christmas I put the car on charge using a snap on battery charger, which immediately stated battery was sulphated and would take Upto 24hr before it could resume charging. Once I came back 2 days later it said bad battery. So i used a different charger to charge it which worked and our midtronics battery tester passed it but it still went flat. I just think the battery is weak! If I install a new battery and tell the car it has one is that it all done? Bmw told me they need a code of the top of the battery to register it? Surely that's for a different amp rating maybe? I don't have the bmw software so can't confirm this. If someone knows the answer that would be nice to know
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02-12-2014, 11:47 AM	#32
umermariner New Member 0 Rep 14 Posts Drives: E60 Join Date: Jun 2012 Location: NJ iTrader: (0)	Did they actually performed load test on your battery and passed it? Seems to me that your battery is severely sulfated, and even though shows normal voltage, would fail under load.
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02-12-2014, 02:14 PM	#34
Dan-danGT Captain 33 Rep 650 Posts Drives: E90 330d M-Sport Join Date: Dec 2012 Location: Nottinghamshire iTrader: (0)	2008 it's as old as my car, bmw want £285 Inc for a battery robbing gits!,
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02-12-2014, 03:15 PM	#36
Dan-danGT Captain 33 Rep 650 Posts Drives: E90 330d M-Sport Join Date: Dec 2012 Location: Nottinghamshire iTrader: (0)	It's got auc warranty so I keep getting them out as and when, I have a problem coming up as it's going in for a remap soon and really could do without it dying during programming it could knacker the ecu! Will get one asap! It's died 3 times, last time they was downloading my files from the dde! But took me ages to get it to jump start! It only does it when ignition is on for 10 minutes. Starts every time if I jump in and press start. I will replace it but 285 is steep for a battery, I'm trying to find a varta with the same rating to sort all my problems lol
	Appreciate 0 Quote

02-13-2014, 01:01 AM	#39
Dan-danGT Captain 33 Rep 650 Posts Drives: E90 330d M-Sport Join Date: Dec 2012 Location: Nottinghamshire iTrader: (0)	Yeah I'm on it today! Does really oem give battery ratings?
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08-13-2015, 04:32 PM	#40
RustyT Registered 0 Rep 1 Posts Drives: E91 320d 2011 Tourer Join Date: Aug 2015 Location: London iTrader: (0)	Overcharging alternator? Hi We have various warning lights coming up on our 2011 E91 320d. They don't stay on for long and it's mainly the ABS but definitely others. They only come on a couple of times a week and usually only for a second or two. We've also had an intermittent problem of the boot lock not activating when you shut the boot. We've only had the car a couple of months and it's been off and on. I took it to a dealer and they diagnosed as an overcharging alternator and that a new alternator 'should sort out most of the problems' but would cost £1000!!! Having read forums, the symptoms do often relate to alternator or voltage regulator issues. However, following tips on forums I have also accessed the hidden menu to find that the voltages are reading around 12.2 when off and 13.8v when idling and revving the engine lightly. From the posts above it suggests that the voltage is OK (or do I need to run it full pelt to make sure it's not overcharging?). I'm now thinking that the dealer might just be going for a quick grand so I'm going to call them to probe them more on their voltage readings. Anyone know if it's likely to be anything else, I.e possible ABS sensor throwing other errors up to? also saw mention or another cable on the battery but can't remember the name but it was related to the charging. Any thoughts on what others think it could be. And hether I'm right to thinking the overcharging diagnosis may be incorrect. I kind of thought this should be clear cut from all the diagnostics but I'm seeing different through my untrained eye. Thanks in advance Russell
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08-14-2015, 05:30 AM	#41
Aragorn30d Lieutenant Colonel 175 Rep 1,596 Posts Drives: E90 330d Join Date: Mar 2015 Location: Fife iTrader: (0)	You need a decent diagnostic scan on the car to see why its bringing on the lights. When lights come on, the ECU involved will log a fault code. 13.8v at idle does sound pretty normal to me. I would say maximum charge voltage for a 12v lead acid was around 14.4v, but these cars to seem to run higher than that for a short time to charge the battery quicker. If its exceeding 15v for any length of time then you risk damaging the battery.
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08-15-2015, 04:25 AM	#42
kiel_dafo_kenyg_as DIE ANTWOORD 68 Rep 640 Posts Drives: 335d E92 Join Date: Jul 2014 Location: Bimmer's home - Bavaria iTrader: (0)	ABS codes can trigger a couple of other (unrelated) codes. Your alternator and battery is fine and your dealer is a douche. Do not go there again. __________________ King of the road says you move to slow
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10-08-2015, 08:11 AM	#43
corsotx10 New Member 4 Rep 24 Posts Drives: e90 325xi (2006) Join Date: Jan 2015 Location: TX iTrader: (0)	My engine running battery is 13.5-7v according to in dash reading. Battery hasn't been changed before. Should I be worried? I do not have any symptoms yet.
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01-01-2016, 04:11 PM	#44
vladmury First Lieutenant 101 Rep 348 Posts Drives: 325d E90 LCI M-sport Join Date: Jan 2015 Location: Denmark iTrader: (0)	320d e90 163 bhp My car this morning did not start since last night all was good. It cranks normally but wont start, i checked the battery voltage was 12 v with engine off then droping at 11.9. When i press the start button, voltage drops to 8,7 V when cranking its normal? After 3rd attempt and a lot of cranking it started, checked with Inpa no errors on engine module. Should i buy a new battery?
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