Battery charge voltage info poll.

**drivesafe** · 16th September 2009, 08:58 AM

If any of you have the time, and has access to a digital multi meter, would you like to 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+% the state at which I find most vehicle’s cranking batteries to be at.

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 info can be from any vehicle, not just your Landy.

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 ) 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 when 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.

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.

A suggestion to make the data entering easier to post, copy the ten questions and paste them in a word processor, add your data under each question and then copy and paste into a reply.

**Redback** · 16th September 2009, 09:55 AM

I can do this, I can even give the data from the Madmans EMS1 battery monitor as well if you want.

Baz.

**weeds** · 16th September 2009, 10:27 AM

happy to help out.....although i do have two aux batteries and solar panel, anything i need to do to get the info for you

**drivesafe** · 16th September 2009, 10:47 AM

Hi and thanks Baz and Kelvin, just post the info up and we can all see whether batteries are fully charged by an alternator or whether there is a problem, as many notable ( B/S ) articles state.

Excuse my scepticism but after 20 years of check vehicle batteries I am yet to come across more than about 2% of vehicles that have batteries that are anything below 90% charged and even then there is usually a reason.

The problem is that there now so many people trying to make money out of convincing people that their batteries are not charging and that they need to spend big bucks to get their batteries fully charged.

Anyway, this test should give some idea of what is happening in the real world.

Cheers.

**Psimpson7** · 16th September 2009, 11:03 AM

Here you go Tim,

1 ) What is the voltage at the cranking battery’s terminals. 12.65v (Car had been off for at least 24hrs)

2 ) Type of vehicle. TD5 Defender.

3 ) What make and type of battery ( a model number will do ) 2xCentury N70ZZ4wd. No smart system, just hard wired together. Ones 2 months old, the other about 13 months

4 ) When was the last time the vehicle was driven. Couple of days ago

5 ) How long was the last drive. 50km

6 ) Is this your day to day drive or a once a week vehicle.. Doesn’t get used that much but then does a yearly trip which can add a few!

7 ) Alternator size 120a

8 ) Is this your tow vehicle or other. My everything vehicle.

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

9 ) What is the voltage at the cranking battery when you first start your vehicle ( cold start ) 14.45 (taken as soon as I could get the probes to the battery after starting. - probably about 10 seconds)

10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive. 14.15 (was 40 minutes)

**Graeme** · 16th September 2009, 07:12 PM

Q9. Exactly when do you want the measurement? - eg during starter motor operation, within 3 seconds of starting, 10 seconds after starting, etc.

**Blknight.aus** · 16th September 2009, 07:23 PM

Originally Posted by Psimpson7

Here you go Tim,

1 ) What is the voltage at the cranking battery’s terminals. 12.65v

2 ) Type of vehicle. TD5 Defender.

3 ) What make and type of battery ( a model number will do ) 2xCentury N70ZZ I think. No smart system, just hard wired together. Ones 2 months old, the other about 13 months

4 ) When was the last time the vehicle was driven. Couple of days ago

5 ) How long was the last drive. 50km

6 ) Is this your day to day drive or a once a week vehicle.. Doesn’t get used that much but then does a yearly trip which can add a few!

7 ) Alternator size 120a

8 ) Is this your tow vehicle or other. My everything vehicle.

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

9 ) What is the voltage at the cranking battery when you first start your vehicle ( cold start ) 14.45

10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive. 14.15 (was 40 minutes)

as per that for big red +/- a bit which may be multi meter variance. but big red is a daily driver, Main battery is about a year old (replaced just after the 100K km service

do you want old school fozzy or just the stuff for big red.

**weeds** · 16th September 2009, 07:35 PM

Here you go Tim,

1 ) What is the voltage at the cranking battery’s terminals. 12.71v

2 ) Type of vehicle. 300tdi Defender.

3 ) What make and type of battery ( a model number will do ) 1 x RACQ 4704, 1 x AMPTECH D87L, 1 x Exide ED6. No smart system, marine isolator thats never used. Age have no idea between 12-24 months

4 ) When was the last time the vehicle was driven. 1hr 30min

5 ) How long was the last drive. 8km

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

7 ) Alternator size 100a

8 ) Is this your tow vehicle or other. My everything vehicle.

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

9 ) What is the voltage at the cranking battery when you first start your vehicle ( cold start ) 13.76

10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive. forgot i needed to go for a drive, will do again in the morning

**drivesafe** · 16th September 2009, 08:31 PM

Originally Posted by Graeme

Q9. Exactly when do you want the measurement? - eg during starter motor operation, within 3 seconds of starting, 10 seconds after starting, etc.

Hi Graeme, if you take the reading about 60 seconds after starting your motor, this will guaranty the alternator is up and running at the required operating voltage.

Cheers.

**justinc** · 16th September 2009, 08:48 PM

And here is mine Tim,

1 ) What is the voltage at the cranking battery’s terminals. 12.56V

2 ) Type of vehicle. RRC 4BD1T

3 ) What make and type of battery ( a model number will do ) Delkor 22FR520

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

5 ) How long was the last drive 12 minutes (Used to be 5 mins...

)

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

7 ) Alternator size 120A

8 ) Is this your tow vehicle or other. Tow, touring, everything

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

9 ) What is the voltage at the cranking battery when you first start your vehicle ( cold start ) within 15 seconds, 13.9V, and climbing slowly
10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive. After 12 minutes, it is still charging at 14.2V
Incidentally, with the SC80 I get 14.2V AT the Anderson plug, too!

JC, (ps did you get my PM Tim? thanks for the help!

)

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