Nice plots here. These are pretty much the exact same info that the AntiGravity battery monitor thing I posted earlier will show you. So there is no need to think about getting one of those. I expect this data will give you the answer.
First question is where exactly is this connected? I.e., what exact voltage is this measuring? Perhaps obviously, not everything in the car that is nominally 12V (or B+ or battery voltage or system voltage, etc.) is actually that. The alternator stud, battery positive terminal, battery positive post, regulated B+ that runs the electronics, etc. You don't generally need to know or care about these differences until you have a problem you want to solve.
When driving it always says charging and voltage around 14v, never an issue. As I mentioned I also added current measure and alternator seems to always provide power to all equipment ok since I don't see any draw from battery during driving.
If it really does
always show ~14V (say 13.6V+) while the engine is running, then there is not a problem with the alternator.
If you check what I said in an earlier post about what the clamp ammeter should be showing, that hopefully explains.
Expanding on what others have mentioned, ...
The way the regulation works is that the alternator itself has a "voltage regulator" built in to it. Setting aside unnecessary and unfortunate complication added by the Honda PCM/ECU and ELD, the VR will control the current (in the neighborhood of zero to 4 Amps) that flows through the field windings within the alternator. This controls the strength of the magnetic field within the alternator. As the drive belt turns the alternator pulley, it moves the alternator rotor, which houses these field windings (current supply is through slip rings to allow it to turn), so the magnetic field rotates. As the field is forced (requires belt force / rotor torque to move it, nothing is free here) to move past the conductors in the stator, current is generated (much greater than the field windings current - up to 100 Amps depending on the alternator design), roughly proportional to engine RPM (rotor RPM) and rotating magnetic field strength.
But this rotating magnetic field strength is proportional to the field current, which is
controlled by the VR circuit. So if the VR sets the field current to zero, there will be no magnetic field and no generated stator current (alternator output current). If the VR set the field current to a max of say 4 Amps, and the engine RPM were high enough, the alternator might output 100 Amps. And if the car was not needing 100 Amps at that moment, voltage would rise, flowing into the battery and literally cooking it. So the VR does not do that.
If the VR is working as it should, the field current will be regulated to maintain 14.4V at the battery. So if the alternator and VR are working properly, you can forget about all these details and just consider the alternator as a constant voltage source.
It will of course be limited - if the 800 RPM max output of the alternator is 60 Amps (for example), and the car needs 70 Amps at that moment, the alternator will be putting out the full 60 Amps, but voltage will drop marginally below 14.4V as the battery makes up for the remaining 10A.
The PCM/ECU also measures total system electrical load (with the ELD), and as a fuel economy complicating optimization feature, may decide that the car is warmed up, electrical load is low, and based on driving needs, the alternator output can be lowered. As I mentioned, I find in my VCM-muzzled car, this almost never happens due to this system thinking the engine is too cool, and I get the full 14.4V (regulated to 13.7-13.8V as displayed on my dash gauge) all the time.
So what you are reporting here indicates no problems at all.
I just went back and read your posts so far in this thread, and don't think there is anything at all wrong. The only problem may be that you are expecting to see a current measurement, but you should not be.
I also have a obdii bt which also shows correct voltages on my phone when I check the volts (CM) data reader of over 13.8volts.
Battery was replaced in Dec, and the battery before was also in good condition and had same issue, that is why I replaced it. Same issue. Two new batteries being bad is highly unlikely from costco.
Do you leave this Bluetooth OBD2 dongle plugged in all the time? Have you measured the parasitic drain due to that?
Agree, not likely to have two bad batteries. More likely that there is nothing wrong with either battery.
I also checked for parasitic draw. It's not that. Because after driving for 1 hour one time and i stopped to fill gas the car hardly started. So it was that battery was already low charge and driving for one hour didn't charge it even though voltage was always showing 14v on my battery monitor during trip.
There is always parasitic draw, it is just a question of how much. You will see battery voltage drop more at first, with the same current, just due to how the battery works.
I would be cautious about drawing a conclusion. Your battery monitor should be showing what is going on quantitatively.
If you can point to a battery plot and indicate exactly what kind of problem you were having when you think it was malfunctioning, that would be helpful.
The reason the voltage was charging at 2am is because the AC charger was connected. Then it stopped when battery was full, and surface charge until morning. Then I drove two times at around 3pm for about 10 minutes with a stop and drove again at 20:18 (ignore this as it was 1 min drive) You can see battery at night was 12.7v indicating it was full from the ac charger. You can see also the short trips voltage was 14v.
Seeing how this plot may have been different if the charger were removed (vs. going into float charge) at 2AM might show what kind of parasitic drain you have.
The drive at 3PM looks perfect. The drop following the first and second drive indicate something kept drawing power until around 4:20 PM when voltage came back up to about 12.6V. 8PM drives look perfect as well.
The "low" cranking voltage is barely lower than expected. I would not consider that a problem by itself. The ripple and time to start (a little over a second) seem OK. A slightly weak battery or worn starter or imperfect connection / cable / ground could explain this.
What was wrong with the first alternator?
BTW, something in all this that I have learned to do over the years with my cars and other things, is to measure and understand them
while they are working well, so I can more accurately know when something is wrong.
Simple, relevant example of that - battery voltage. There are people on the intertubes demanding that your battery is worn out and dead if it ever reads below 12.6V. That is of course wrong, but what I've done is to measure my battery when it is brand new, checking voltage (via the dash gauge) when I get in the car in the morning, after a day or a couple of weeks, pay attention to how it works, etc. Answer is that I will often see in the low 11 Volts range, and the car starts perfectly every time, with a new battery, and with the same battery after 3 years.
