Thread: Battery Voltage

Originally Posted by Road Stone

The suggestion their end is that these batteries are very good and its more likely that my alternator is tired. 13.7v charging at idle is low.
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not sure i agree with that,13.7 isnt that low. depending on the car, 13.7 is normal

Hi Jerry, at this stage, until you get yourself a multi meter, don't worry about what voltages you are getting right now.

Also, don't get a cheap multi meter, try for around the $20 to $40 mark and you will be fine.

If you can, see if you can get one that turns itself off after 10 minutes. There is nothing worse than needing to get a voltage reading off something important and when you find your MM, you realise the last time you used it, 6 months ago, you left it on.

Originally Posted by bacicat

Maybe lash out a bit more than this - it doesn't do DC current so useless on vehicles...

Fair cop. I didn't read all of the fine print in the description. This one is an all round better meter.

http://pages.ebay.com/link/?nav=item...877141&alt=web

Aaron

Originally Posted by Aaron IIA

Fair cop. I didn't read all of the fine print in the description. This one is an all round bettet meter.

http://pages.ebay.com/link/?nav=item...877141&alt=web

Aaron

Yep.

Originally Posted by Aaron IIA

Fair cop. I didn't read all of the fine print in the description. This one is an all round better meter.

http://pages.ebay.com/link/?nav=item...877141&alt=web

Aaron

Okay thanks for that. Plenty to learn!


So I have used the car frequently over the last few days and did the same test today.


This again is on the diagnostic tool:


Battery Voltage engine off: 12.3 (vehicle has sat for about 18 hours)
Battery voltage engine at idle: 14.2 -14.5 (left it longer this time to settle down).


I'll report back when I have the MM and learn how to use it.


Thanks Jerry

Hi again Jerry, and with 14.2+v, your alternator charge voltage is fine.

The 12.3v battery voltage ( around 70% SoC ) is not that low especially if, as you say, you have been using your RR ?frequently? over the last few days.

With that alternator voltage, if you had been driving for a decent amount of time, each time you drove, then I would expect to see a little higher voltage, say 12.4, 12.5V.

But, as I suspect, you have probably been doing short drives, of 20 minutes or less, and if so, then you are not only not allowing the alternator to fully charge your battery, you are actually using more energy to start your RR than you are replacing while driving.

If you have a multi stage battery charger, preferably no bigger than a 10 amp one, try giving your battery a few good soak ( conditioning ) chargers.

You do this by first allowing the battery charger to fully charge your battery, and this may take quite a few hours with a small charger, then once the charger goes into float mode, leave it on for around 8 to 10 hours, then remove the charger for at least 10 to 12 hours.

If you can, do this a few times, even if you have to use the RR between charge cycles, you may find the settled voltage of your battery will rise.

Continual short drive, the Shopping Trolley Syndrome, is probably worse for cranking batteries than leaving them unused for a week at a time.

Maybe purchase a CTEK or something similar when you are in Brisbane if you don't have for battery maintenance.

Cheers

Originally Posted by bacicat

Yeah, 12.6 to 12.7 is fully charged. 12.1 is quite low. What sort of voltage do you have while it's running? You should have around 13.8 to 14.0 on these.

With my L322 Vogue 2003 4.4L I seem to get the same or similar voltage when running and with ignition off.
13.8 - 14.1v at idle 750RPM and about 12.5v with power off.
Funny part is, the battery will go flat after about 7 days if the vehicle is not used at all.

New battery fitted a month ago (big sucker) as per specification made no difference.
Might need to check if the alternator is bleeding backwards, hey?
Oh the fun never stops.......

Cheers, Shirley.