Right now, I'm just monitoring voltage from a power outlet in the console. I'm generally doing so without any additional loads on that circuit, and when I have correlated the monitor with the battery directly (with a meter at the battery) they seem to be the same voltage. I believe the accessory plugs are disabled when starting the car-- I don't recall seeing any voltage shown AS I start the car.Regardless, you still have a voltage to the alternator field that, in your case, is controlled by the car's computer. In older cars, the field voltage was controlled by a voltage regulator, that was internal to the alternator. If you can monitor that field voltage, while you are driving, that would be a big help.
Also, and unless you have a huge load on your system, a fully charged battery, will not immediately drop below 12 volts, even if the alternator shuts down.
Of note, if you monitor battery voltage while starting your car, the voltage shouldn't drop much below 9 volts. The starter is a very, very large short term load.
Also, the Torque app, for the Android phone, along with a Bluetooth OBDII adapter, total less than $20, can monitor and store alternator voltage while you drive.
I'm having no problems at all with the car starting-- not even slow starting. I'm having no problems with the car charging either, but I'm getting warnings, and I don't want some small problem to strand us hundreds of miles from home...
The Torque App sounds interesting but I'm an iPhone guy-- I'll have to see if there is an iPhone version or some similar solution I would love to be able to review a log of the voltage recorded through the OBDII
I'm not sure one can monitor that field voltage in a useful way-- the mechanic I talked to explained that this is a modulated signal-- switching on an off rapidly to control output voltage from the alternator.
Something I didn't post because it seemed unrelated-- my air conditioning went out right when all of this started. No direct correlation perhaps, but I stopped using it when the compressor started short cycling, and turned off all the accessories possible when the chiming started to happen as well.
I'm told that 12.5 - 12.7 volts is to be expected under low-draw situations when the car lightens the alternator load to save power, and the voltage will then cycle up and down to maintain a charge on the battery, or cycle up and stay up with sufficient load applied.
This is outside my experience, but for a couple of days, I've been test driving it-- the A/C has been fixed, so I'm back to being able to run it all the time-- basically I never turn it off under normal operation, so having it off was really unusual.
With the A/C back on, and the radio & navigation operating and no special consideration to reduce power loading, today, the car started up around 14 volts, then leveled off in the 13.5 to 13.7 volt range. Lowest noted voltage was 13.3 when idling in a carol line, in gear with the AC blasting... That's far from conclusive, but pretty interesting. With no accessories on, a few days ago in the same situation I had roughly 20 warning chimes and nearly sixty noted low voltage excursions within a single hour. Today, the same ambient conditions existed. Same car, same driver, same driving route, again for around an hour, and zero alarms, and zero low voltage excursions by the meter.
It is all quite confusing.
It all makes my head spin...