D3 ALTERNATOR AT 16+VOLTS???????

[kingo]

My D3 has always run at high volts, 15+, but eventually it hit 16.3+. At the recent service it was replaced as it was flagged as the issue. On the weekend on a LROCV trip I could smell what I eventually realised was the Optima yellow top second battery cooking, it was so hot the top has deformed slightly.

I have disconnected it, the voltage is still 16+ whilst the car is running. I have noticed the main battery is probably getting old and was showing 10.5v the next morning. The car still starts perfectly on the main battery, even after the 2nd was disconnected.

The question, is it an alternator issue or could the main battery cause the overcharging issue? I noticed it was only the Optima suffering overheating/boiling not the car"s main battery.

I'm using a Projector isolator, however don"t think this the issue. The car has always seemed to be high on the volts even before I added the dual batteries?

Love an expert opinion as its heading back to the specialist tomorow and don"t want to throw more money in the wrong direction

Cheers

Andrew

[Graeme]

To what is the aux battery's negative connected - the main battery negative or to the body?

[Landie333]

12v is a bull shoot figure in charging systems now. Most alternators in modern vehicles are output controlled via the main engine computer. Anything under 14v is bad and the regular charge rate can be anywhere from 14v to 16-16.5v That is on systems that have a Battery sensor. The way you can tell is if there is a small box with two wires on the negative main battery cable.

[kingo]

Second battery earth is connected to the earthing bolt next to its location. The Optima was showing 13v the next morning after it was disconnected the day earlier, maybe it isnt stuffed. Would have thought 16.23 volts to be excessive and the cause of the Optima boiling though.

[Glynhouse]

Not to sure about those voltages ?
My alternator was replaced 8000klms ago, old one definitely had it, fitted a volt meter when we were having trouble, the new one goes to 14.4 fairly soon after starting (couple of minutes) but then drops back to 13.6 volts very quickly and stays there.
Very low to me, but I am assured by L/R that is correct, the old battery I replaced after 6 years as I was doing a long remote trip and I don't like batteries at that age ! So it certainly did not harm the old battery.

DD

[drivesafe]

Hi DD and that is normal running voltages for a D3.

Kingo, the next time you are near a dealers, get them to check if there is a software upgrade because that is normally a software error not an alternator fault, and to have two in a row, your dealer should have tweaked to the problem.

[kingo]

Hi Drivesafe could the low voltage on the main battery trigger the oversullpy from the alternator?

[drivesafe]

Hi again Andrew and your low cranking battery could cause that sort of problem but I’m not sure of your voltage readings.

To have a cranking battery at 10.5v and still be able to start the motor, is not normal.

A battery at 10.5v is dead flat and would not even bring the start motor into play.

Now as you posted, if the cranking battery is flat and the D3’s BMS runs the voltage at a higher level, it will eventually drop back down.

Here in Australia, the D3 BMS will usually only run the voltage as high as 15.5v and only for about 30 minutes after you started the motor for the first time on that day.

This 30 minute high voltage charge should not be long enough to cook the auxiliary battery.

The voltage would normally drop to maybe 14.5v but usually drops to high 13v.

There is a known problem with the motor to chassis earth lead, where the chassis mount corrodes and needs cleaning. This usually just stops the batteries charging and does not cause high alternator voltages but on any other type of vehicle, this can cause high voltages.

Let us know what you find.

[kingo]

Have just picked the car up from the mechanics and they replaced the main battery. They checked the voltage and then when it was connected to a healthy battery the voltage settled down to mid to high 14's, also what I would think is normal.

However it looks like the Optima yellow top is stuffed and didn't pass a load test, another $400 at some stage.

Might be getting time for a new D4, as maintenance is out waying the cost of a new car.

I do like the idea of a new D4 though, so wont be hard to convince myself.

[drivesafe]

My D3 has always run at high volts, 15+, but eventually it hit 16.3+.

Hi again Andrew and good to hear you got it sorted but I would still watch your voltages.

I have read of voltages that high in the UK ( caused by the much colder climate ) but even then they were only high for a short time.

Has anybody else seen voltages this high, here in Australia?

[smwilk]

Mine has only ever reached 15.2V. I'm onto my 2nd optima with a deformed lid. Still ok though but I wonder for how long.

[drivesafe]

Hi smwilk and any idea why the Optimas are deforming.

Mine is 7 years old and is now being used as a cranking battery in the wife’s car.

Still going strong.

[smwilk]

No drivesafe, I haven't looked into it, believe it is heat from within?

[jonesy63]

FWIW, my D34 Optima also deformed - at the bottom of one of the 6 cells. That was after 4 years in my D3 and 1 in D4.