Charging voltage while running?

iminhell1

Sergeant
Jun 17, 2018
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Google is trying to sell me a voltage regulator and not providing any good info. Google, ya broken. Go home and fix yaself.


It's something I never log and right now it just seems low, 13.44 at idle with accessories off.
I could have swore it should be in the low 14v range, and was previously. But memory being what it is I can't be sure. Hoping someone else can be my brain for a short time here.
 

dyezak

Major
May 4, 2017
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Plano TX
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335is
RPM increases voltage as it spins the alternator faster. To see what you're run time charge rate is take your measurements at 2000-2500rpm. That's where the accessories are designed to be spinning as the car is driving down the road. This is why charging your AC is done at that RPM too.
 

aus335iguy

Colonel
Nov 18, 2017
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Down under
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335i DCT 2009
There’s also the energy recovery system that stops it charging at certain times. I remember looking at it in the dash and it would t charge whilst driving except when decelerating or braking.
 

iminhell1

Sergeant
Jun 17, 2018
345
156
0
There’s also the energy recovery system that stops it charging at certain times. I remember looking at it in the dash and it would t charge whilst driving except when decelerating or braking.

That is part of the 'eco mode' of the newer BMW's. The E8x and E9x cars don't have that option.


Seems that I'm mid 13.xx at basically any RPM. Stable. Just seems low vs other cars I've worked with.
 
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Milan

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Dec 24, 2016
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jebi se
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your mom
That is part of the 'eco mode' of the newer BMW's. The E8x and E9x cars don't have that option.


Seems that I'm mid 13.xx at basically any RPM. Stable. Just seems low vs other cars I've worked with.

I think the E90 M3 turns off (declutches) the alternator at WOT though
 

aus335iguy

Colonel
Nov 18, 2017
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Down under
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335i DCT 2009
That is part of the 'eco mode' of the newer BMW's. The E8x and E9x cars don't have that option.


Seems that I'm mid 13.xx at basically any RPM. Stable. Just seems low vs other cars I've worked with.
Mines an my09.5 and it has it, you can see the charge change in different scenarios.
 

pdxbimmertech

Lurker
Dec 18, 2017
21
9
0
Portland, OR
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2008 E92 335i 6 spd
DME is in control of the alternator via BSD line and does vary the voltage based on demand. From what I've seen so far with alternator failure they usually will over charge up to around 17V.
 
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Optigrab

Corporal
Sep 19, 2018
133
56
0
Ride
08 135i
I checked my service manual this is the most relevant thing i found.

Charging system quick-check
- Use a digital multi meter to measure voltage across the battery
terminals with ignition OFF and then again with engine running.
Battery voltage should be about 12.6 volts with key OFF and
between 13.5 and 14.5 volts with engine running.

- Run engine at about 2000 rpm and switch ON electrical loads (fans,
lights, rear window defroster, and wipers). With all accessories on,
battery voltage should be above 12.6 volts.

The regulated voltage (engine running, battery charged,
accessories and lights OFF) is usually between 13.2 and 14.5,
depending on temperature and operating conditions. If the voltage is
higher than 14.8, the voltage regulator is most likely faulty.
 

MacBB55

Specialist
Jul 22, 2018
80
6
0
Northern California
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2004 BMW 525I
ok so im wondering if the readings would be the same using multi meter on battery terminals and the readings I get from the hidden obd menu we have in our cars as well as the reading I am getting from my cig lighter socket from a Bluetooth charger thing that displays the voltage of the car as wel for some reason, I get that the terminals would probably give me a more accurate reading but I just wanna know if u think these other options of looking at it would be somewhat close?
 
Apr 1, 2017
158
36
0
Ride
E92
That is part of the 'eco mode' of the newer BMW's. The E8x and E9x cars don't have that option.


Seems that I'm mid 13.xx at basically any RPM. Stable. Just seems low vs other cars I've worked with.

If you are referring to the intelligent alternator feature ... it can be enabled. Voltage would then go up to 14.8v at times for rapid charging ...
 
Apr 1, 2017
158
36
0
Ride
E92
Is that default on for certain years and or do we have to code that sep if we swapped to agm

If you drop in an AGM battery then this would be useful since the AGM battery is made to do intense charging. It’s not default on and has to be coded.

It’s interesting how this will affect spark dwell when multi sparking is turned off ...
 

Optigrab

Corporal
Sep 19, 2018
133
56
0
Ride
08 135i
If you are a DCT and put in a smaller capacity battery and dont code the battery, It can cause the DCT to have strange behavior
 

Rob09msport

Major
Oct 28, 2017
1,928
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Monroe CT
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09 335i msport le mans 18 x5
If you drop in an AGM battery then this would be useful since the AGM battery is made to do intense charging. It’s not default on and has to be coded.

It’s interesting how this will affect spark dwell when multi sparking is turned off ...
Why would it affect dwell and would you be willing to post or PM the parameter I understand if not I don't know how secret that info is.
 

Optigrab

Corporal
Sep 19, 2018
133
56
0
Ride
08 135i
I believe just general livability issues it was with a 135 over on 1 addicts.
 

Optigrab

Corporal
Sep 19, 2018
133
56
0
Ride
08 135i
I mean drive ability lol

Replacement battery registration
After fitting a new battery, connect BMW scan tool or equivalent and
run service function "Register battery replacement" to notify vehicle
power management (software in the engine electronics and
intelligent battery sensor) that a new battery is fitted in the vehicle.
Without new battery registration, CAS and vehicle power
management does not run properly and this can lead to function
limitations; for example: reduction or deactivation of individual
consumer functions.
During battery registration, the following operations are performed:
• Current mileage is stored.
• Stored values from old battery (charge status, current, voltage,
temperature, etc.) are deleted.
• Power management is initialized.
 

iminhell1

Sergeant
Jun 17, 2018
345
156
0
If you drop in an AGM battery then this would be useful since the AGM battery is made to do intense charging. It’s not default on and has to be coded.

It’s interesting how this will affect spark dwell when multi sparking is turned off ...


I think we're all ears ...