Lots of talk on the forum just now about battery voltages and alternator voltages, so I thought I would check mine.
Checked battery, car not running, 11.9v
Car running, 14.2v
Checked with a calibrated voltmeter.
When I use the 753 menu the highest voltage I read was 13.5 so that is why I thought I would manually check it.
The car has not been used a great deal in the last 2 weeks with holidays etc so I think my battery needs charged a bit, but I am happy the alternator is giving out more than the 753 test says.
So, the point of the post is, the 753 test reading is lower than actual and in my case and scared me into thinking the alternator was on its way out, which is not the case.  Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

Question, TDV8 - does it have an intelligent alternator (i.e. to aid mpg does it disengage?). I only ask because I note that using 753 it sits at 14v then drops to 12.5 and stays there a while then goes back up to 13,13.5 14 .... Land Rover Addict
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2009 5.0V8SC Autobiography
2006 4.2V8SC Autobiography
2004 4.4V8 Vogue

Don't know if the alternators are intelligent. I have a new alternator, well 1 year old, on a MY08 TDV8. 753 readout always shows at least 0.5v less than a calibrated voltmeter. I have tested several scenarios:

Resting charge (engine off, car 'asleep') 12.9 volts
tickover - 14.2 volts
tickover torture (everything on - stereo, lights, heated screens/seats/wheel, screens in the back, dvd player, phone charger etc etc immediately after starting the car) drops to 12.6 volts,

2000 rpm torture - normally picks up to about 13 volts.

Whether the alternator is smart or not, it is only just capable of running all the systems in the car concurrently whilst being able to add some charge. I notice this most with the screen program on the HVAC, when you hit the preset to demist the screens both front and rear screens energise and the fans blow air at the screen, but the blower never seems to get much past 50%, until you turn off one of the heated screens (in my experience it doesn't matter which) and then you get an increase in the airflow/fan speed. So there is some intelligence to the management of the electricity in the car, but maybe not at the alternator end.

Surprisingly difficult to measure the battery voltage accurately on an FFRR.
Opening any door brings the car to life and for a few minutes the current draw can go up to 7-8A, this current drain gradually goes down over about 15minutes until the car goes to sleep again.
The current draw on awakening results in a voltage drop on the battery of about 0.4-0.5V.
Therefore if you open the car, even the bonnet, and then immeadiately measure the battery voltage, it will be reading low.
You really need to leave the car to go to sleep after opening giving the battery time to recover, I would suggest about 30-40minutes.
I get round this by having a voltmeter plugged into the front ciggy socket with the display readable thro a window. Also good for measuring alternator output voltage on the go.
11.9V on a battery is a bit low, could be just it didn't have time to recover.
14.2V on the alternator is very good.

 Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI