VE SV6 2010 alternator charge

[kakao]

Hi guys,

just replaced alternator on my car and noticed the following:

- when I start the car and measure the voltage at the battery terminal it reads 14.7V

- after 20min drive I have measured again and the reading was 12.8V

Is this normal? I take it that the alternator should charge at 14.7V or so constantly, or maybe there is some 'regulator' that drops the alternator charge after some time?!??

Please let me know your opinion, cheers!

 

[syked]

Mine does the same. I think it's normal behaviour because the BCM controls the alternator voltage and it knows it doesn't always need to pump 14.7V to the battery

 

[HarryHoudini]

Mine rarely drops below 14.7 or 14.9,even on long trips.I thought the Battery was tired and replace it but the new Battery is the same,always 14.7 or 9 showing on the voltmeter(cigarette lighter socket).

 

[Banjo79]

Mine rarely drops below 14.7 or 14.9,even on long trips.I thought the Battery was tired and replace it but the new Battery is the same,always 14.7 or 9 showing on the voltmeter(cigarette lighter socket).

Same here. Got a new battery and it worked properly for a day or so, dropping to high 12's within a minute or two like it did for the first few years. Now it doesn't drop below 14.3 and gets up to 15.1.

 

[1997 VT Calais Series 1]

Hi @kakao

Yes, that appears normal.
You mentioned that - when I start the car and measure the voltage at the battery terminal it reads 14.7V
Then you mention - after 20min drive I have measured again and the reading was 12.8V

If you think about it, all the electronics are being used in the car as you drive it and they will drain power, even if your alternator is meant to charge the battery as you drive. My suggestion would be to? Place your car battery on a low cycle charge every night when you park the car (If you can, as I understand that some may not be able too) this will ensure that your battery is fully charged when you start the car.

Things to remember?
Battery life is drained from a battery every time you start the car.
That battery life that was drained from starting the car is lost forever (and over time the battery eventually dies)and the use of electronic in the car also have an effect.
The alternator recharges the battery to the best % possible.
A warning light on the dashboard glows when the battery is not being adequately charged or holding a charge.
Another practical example is? When the engine stops and the warning light is on.
The reading on your dash is an indicator of how much voltage life is left in your battery, and those numbers will change when the vehicle is in operation. If the voltage numbers start getting lower and lower it is an indication that? 1) the battery is losing life, 2) The alternator is not charging the battery correctly.
Both situation should generate a warning light on the dash.
To test the battery? You will need to buy a battery tester, or some auto electricians may do it for free, this is the first thing you check before replacing the alternator. If the battery passes, then you move to the alternator.
Another way is by a scan tool.
Hope this helps

 

[kakao]

Thanks everyone for their input.

I believe the bad alternator was my problem. Since I installed new alt I have noticed that the car is going better, its more responsive (even my wife noticed that LOL).

 

[snortings]

They are a smart alternator, it will vary up and down when it needs.

 

[kakao]

They are a smart alternator, it will vary up and down when it needs.

From what I have measured in the last week or so this appears to be the case. It never drops below 12.8V charge.