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Discussion Starter #1
Hi folks, if any of you have the time, and have access to a digital multi meter, would you kindly take part in a simple battery voltage test.

The idea of the poll is to see whether cranking batteries are not being charged above the 70% level that is proposed in quite a few articles or is it more like 90+% as I have posted about.

There are 10 basic questions and just answering the first will do, but if you have the time and info available, answers to any or all of the other nine would be very helpful in see just how alternator battery charging works in different vehicles.

The first question will be more accurate the longer the vehicle's motor has been off, preferably 12 or more hours after the motor was last on.

1 ) Once the motor has been off for a few hours, preferably 12 or more, what is the voltage at the cranking battery’s terminals.

2 ) Type of vehicle.

3 ) What make and type of battery ( a model number will do )

4 ) When was the last time the vehicle was driven.

5 ) How long was the last drive

6 ) Is this your day to day drive or a once a week vehicle

7 ) Alternator size

8 ) Is this your tow vehicle or other.


If you can, the following info would also be of interest.

9 ) What is the voltage at the cranking battery about 1 minute after you first start your vehicle ( cold start )

10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive.


The last two questions are for gaining a better idea of how different alternator operations. Alternator operation in most vehicles is now controlled by the vehicle’s Engine Management Computer. This independent control not only means that there will be differences in alternator operations between vehicle makes but even between same make and models.

I Had an 03, Mark III Range Rover, first version of the current model. It’s alternator went to 14.3v soon after the motor started and stayed there for as long as the motor was running.

I now have an 08 Mark III Range Rover, the latest version of the current model. The alternator in the 08 RR does not start generating power for about 30 to 50 seconds after the motor is first started and the initial voltage can then be anything from 14.2 to 14.9 volts and does not seem to be influenced by ambient temperatures.

Exactly 30 minutes after the first start, the voltage lowers and can be as low as 13.2v.

So info on how the different alternator operations would be interesting to see.

For anyone trying to get any form of alternator operations info, it is almost impossible to get any data form any of the manufacturers, so your input can be very helpful.
 

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Discussion Starter #2
An example of the type of data collected

This is an example of the type of data collected, this is the info from testing Subaru Forester

1 ) Once the motor has been off for a few hours, preferably 12 or more, what is the voltage at the cranking battery’s terminals.
1 ) 12.62v

2 ) Type of vehicle.
2 ) Subaru Forester Sports

3 ) What make and type of battery ( a model number will do )
3 ) Make? Type = 55D32L = 48 A/H Flooded Wet Cell

4 ) When was the last time the vehicle was driven.
4 ) 16 hours

5 ) How long was the last drive
5 ) 25 minutes

6 ) Is this your day to day drive or a once a week vehicle
6 ) Daily drive, average drive time is 45 minutes

7 ) Alternator size
7 ) 110A

8 ) Is this your tow vehicle or other.
8 ) Shopping trolley and to and from work transport

9 ) What is the voltage at the cranking battery about 1 minute after you first start your vehicle ( cold start )
9 ) 14.55v 1 minute after a cold start

10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive.
10 ) 14.32v after a 25 minute drive
 

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2010-2012 Range Rover MkIII / L322
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4,635 Posts
I think the later models must have a more advanced charging system. The L322 certainly has had several supercessions of battery part numbers (meaning the rating and size has changed) and anyone who has fitted one will know that it is about as powerful a battery as will fit in the battery tray. Can't comment on the alternator.
 
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