On battery voltage, I recall finding a constant offset of about 0.4V between battery voltage as measured at the battery, or at the engine bay battery port, vs. what the cluster would read. The cluster would read lower.

And for debugging purposes at least, I'd hook up a charger and keep that battery charged up to see if anything changes. 12.2V does not sound too low to me, but yes it should be a little higher if it's measured at the battery or engine bay. But it could maybe indicate less than ideal charging. A plug-in charger would eliminate that doubt while you're tracking this down.

:iagree:

And the advantage of the cluster voltage display is you can leave it up while driving and if you have an intermittent alternator or charging system, you can spot this while driving. You should see at least 13.8v on the cluster display while driving - indicating about 14.2v-14.3v on the battery bus.

And since you have mentioned parasitic drain, I guess that's another test to add to your list.

Ok, i've let the vehicle sit over night in the garage
Key was in the ignition, vehicle unlocked.

Unlocked Cluster, went to PR.09 (Battery Voltage)

UB: 11.5V (wow, that is stupidly low)

Removed the key, re inserted, all the dash lights come on, fuel pump running, started the vehicle as per normal.
No slow cranking, it started just fine.
(at this point i am wondering how a battery indicating 11.5v can even do this?)

Reversed vehicle outside
While engine still running, i went back into the Service Menu and back to PR09

UB: 13.8V (engine running)

That seems a bit low to me, i'd expect 14.4v
13.2v is a float voltage, so 13.8 isn't much more.

NOW the worrying part.

I turned the vehicle off once more (to get out of Service Menu)
Went to turn the vehicle back on..... No Starting, No warnings lights come up in Position 2, but the radio and interior lights all work.
But the vehicle now no longer starts (again).

So one clear and obvious problem would be an under voltage battery.
But why? Is the Alternator not doing its job?

We have had Battery issues in the passed, similar to this.

The only thing i have done different to this vehicle in the last month
Was to charge the battery while in the vehicle using the engine bay terminals
(normally i remove the battery terminals and charge it, as i am terrified of causing damage to some sensitive electrical module)

Used a Noco Genius G7200 on AGM setting.
One interesting point, was the Noco took 4hours to reach 100%, then i thought i'll leave it on for a while longer, just let it tender and when i came back 1hr later, the was back to 25% and starting the charging process again?

Agreed oldskewel.

The Low Tire Pressure warning is very sensitive, 2lbs difference will set it off.
I'd say its come on a few times over our life with the vehicle, twice there was an actual Low Pressure or Flat tire, the rest of the time it just seems to get out of sync after a few 1000 kilometers.

And yes, a Low Battery voltage sends this vehicle into crazytown, i remember the Trans Fail fault being thrown last time we had low battery voltage issues.

I am about to remove the +Ve from the Battery and connect my Amp meter in between to check what current is being drawn from the battery when this vehicle is parked for the night.

Battery Voltage test

Battery Voltage on the Battery disconnected from the vehicle is 12.04v

http://www.aussiebatteries.com.au/as...ge-website.jpg

Current Draw Tests

Vehicle off, but interior lights on, current draw from the battery is 8.7Amps!!!!

Key out, Interior lights OFF, all doors shut, draw from battery is 3.65Amps!!!

Does that seem right?
Close to 44watts being consumed while the vehicle is parked?

When i used the meter to measure current, i heard the CD stacker or maybe the GPS DVD searching and fan blower running
Interesting considering there was no key in the ignition.
This post is could be helpful: https://xoutpost.com/255823-post6.html

EDIT: Apparently 3.64 Amps is not what it should be, more like 15 to 30 milliamps!!!!
https://xoutpost.com/bmw-sav-forums/...ad-solved.html

The only thing i can add, is the CD Stacker in the back stopped working a little while ago, i think it has a jammed CD in there
It will not ejected!
Maybe i can just remove the unit and see what happens

Also our Radio Module in the boot/trunk has also had the Output Amp Stage repair so all speakers work.

Another interesting thread: https://xoutpost.com/bmw-sav-forums/...drain-e53.html

What is important in the drain test is what is being drawn once the car goes to "sleep" - about 16 minutes after the last door is closed etc. You can tell the car has gone to sleep once the orange LED next to the gear shift goes out (look through the windows - don't open the door!). :D

The cluster voltage reading seems about right - remember it reads about 0.4v-0.5v lower than the battery bus actual value. "UB: 13.8V" on the cluster is exactly what you want to see.

Thanks Wayne, i'll do a proper Current Draw test and watch for sleep mode now.

Appreciate the advice.

Might need to make the meter accessible without opening a door etc. - the current range may need to be switched - when the car is asleep the current draw should be under 50mA - with ~40mA being "typical". :-)

Thanks mate, that range is currently in Amps 1-10Amp scale.

I'll let it to this test, then do it again in mA's
Hope i don't toast the meter in the mA scale though