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Post by ptbinao2765 on Jul 7, 2024 14:19:03 GMT
In my experience as auto mechanic (more than 15y) I was frequently forced to test some car alternators to ensure that they were doing its job and charging the battery whenever the engine is running.
I noticed that Obd eleven has a feature that tells you to e status of the battery and even tells you that indeed is charging as one can see the Voltage going up and the icon changes to green with a charging bolt symbol.
Is right to assume that the alternator is doing its job or this measurement is not direct result from this parts feedback?
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Post by dv52 (Australia) on Jul 8, 2024 0:40:22 GMT
As you will be aware, the ONLY true voltage reading for a car battery is when the meter is connected directly across the battery terminals. Of course, OBD11 can't do this because the dongle plugs into the car's OBD port.
Therefore and whilst I have not seen any official explanation, my hunch is that the voltage reading that OBD11 shows is at best a measurement at pin #16 on the OBD connector (which is a Terminal 30 voltage). This means that the reading is necessarily affected by volt-drop on the down-steam side of the wiring, circuit-fuse and connectors en-route from the battery terminals to the OBD port! So, not the same as measuring REAL battery rail volts!!
As for the different categories of battery health that OBD11 software shows, these are only very broad indicators IMO and I wouldn't suggest that they are a substitute to taking proper measurements with a good quality meter. That said, the fact that the OBD11 battery images change as the alternator voltage increases is of some benefit in diagnostic testing - I guess!
If you want to learn more, use the help feature and search for "voltage". The information about "gauges" should show this:
As you can read- really ONLY broad categories of battery health!
Don
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Post by ptbinao2765 on Jul 8, 2024 13:46:04 GMT
Hello dv52 , Thanks for the fast reaction and for the explanation. i would like to further reuqest your opinion on this because when analysing the diferent battery status icons you have overcharged as not charged at all. When conected to the veichl, one can see the current voltage supply (to the obd port) however if the obd port checks it as 14V (per example as it is when the engine is running) , it should mean that indeed 14V are beeing produced, thus the alternator is working as expected even though the reading is not direct. My question is , in a quick and very shallow way when one is conected to the Obdeleven device, one can see how the alternator is working, or how is the health of the energy on the battery. do you agree? I understand that the proper measurment will always be DIRECT AT THE BATTERY . Thanks a lot for the support ![]() ![](//storage.proboards.com/6321844/thumbnailer/RcbDggvnXmB0L0gsKivB.png)
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Post by dv52 (Australia) on Jul 9, 2024 0:03:47 GMT
In your example, if the OBD11 voltage image shows a rise to 14 Volts when the engine is running, the fact that the measurement is significantly .higher than when the engine was NOT running (and somewhere near 14V) is a good indication of a properly operating alternator. BUT, my point is that this is ALL that can be assumed about the health of the car's battery-charging facility from the OBD11 battery image!
As we both agree, further tests with an actual good quality voltmeter is required to conclude that the REAL battery rail voltage is OK! So, I suspect that we are both in heated agreement! Don
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