I am hoping someone can help explain the alternator voltage situation I have observed with my 2014 RDX Tech 2WD. I have had the vehicle for 9 months. I do not drive the RDX every day. It may sometimes sit in the garage for 3-5 days. One morning, the starter cranked funny, so I measured the battery voltage and found it to be 12.14 volts – this is about 27% charge. I recharged the battery and noticed it took a long time to recharge (sulfated?). When done I reconnected the battery cables and went to bed. The following morning, the voltage had dropped down 12.42 (75% charge). I recharged the battery a second time, and when done the voltage reading was good (12.70) but the CCA reading was 450 which seemed low (I believe this vehicle requires around 500-550 CCA?). This time I left the battery cables disconnected, and the following day the battery measured 12.50 volts (50% charge). At this point, since the battery was not holding charge, I concluded it was bad and decided to just purchase a new battery. With a new battery installed, I wanted to confirm operation of the alternator, so I decided to monitor the charging voltage. I hooked up an electronic volt meter to the 12 volt port in the center console and drove around town. I believe Acura’s Energy Management System varies the alternator output voltage anywhere between 12.5 to 14.5 volts. As I monitored the voltage, I noticed that when idling, accelerating and cruising the meter would read around 12.38 – 12.40 volts. It was only during braking and deceleration that the voltage would momentarily increase to 14.32 volts or so. This is not making sense to me. My readings were 12.38 – 12.40 volts about 95% of the time. This is not even battery voltage. And what would seem like a charging situation was for very brief periods of time. This is not frequent or long enough to keep any battery charged. Can anyone help explain this? Has anyone experienced a similar problem with their 2014 Acura? Are any Acura technicians aware of any on-going problems related to this or any PCM reflashes issued by Honda to correct this? Could the battery sensor be defective? It seems quite obvious to me that this could have at least contributed to damaging my battery. I was hoping to get some opinions before I contact the dealership. Thank you.

 

take it in. You need over 13.5V to get a battery charge on and preferably lower than 14.8V My Acura runs at 14.7X (2002 CL-S) and it is very constant even in the winter with the rear defroster, A/C and seat heaters going.

 

UPDATE: Thank you YeuEmMaiMai for your response. I agree 100%. Here is what eventually happened for the benefit of those who might run across the same situation. A few days later, after driving the vehicle some more, the volt meter read 14.28-14.35 volts. From the times I peaked at the meter, at no time did I catch a reading lower than 14.28 volts. So this now seems more like a normal charging situation and more in line with what I was expecting. I am still perplexed at what caused the initial readings I got, considering I drove for 40 minutes through traffic lights and highway driving, long enough to see some kind of change in charging behavior? Perhaps the charging system responded to the presence of surface charge on the battery by limiting or preventing the alternator from further charging it? Anyway, static voltage and CCA readings for the new battery are also good, so it seems like everything is okay. I will continue to monitor the charge situation. As for the factory battery, there is no doubt in my mind it was defective (sulfated) based on how it responded to the charge and the low CCA reading I got. It amazes me the factory battery lasted only nine months, but I have read and heard more than once that these factory batteries are of poor quality and usually do not last beyond a year.

 

Newer cars have an Electrical Load Detector and vary the output of the alternator. My 2003 Subaru Runs at anywhere from 13.8 to 14.2

 

Hi AZ community,
I am having same issue with my 2007 Rdx tech, what happens in my case is that battery would suddenly die completely - car won't start, even displays won't come on, nor cabin lights. My wife would drive the car to work, park for few hours then would find its dead... Happened twice already, both times car had to be jumped, then would run ok for a few days... So I assumed its battery, since once jumped the car would charge it and would run ok for some time. Then I hooked up my auto voltmeter to 12v outlet just like OP, and observed that when accelerating, crusing - when engine under any load, the voltage would drop to 12.5 +-0.3 or so, but when I would stop or shift to neutral the voltage would go back to 14.3 - 14.5 range, that's very strange as per service manual it should be no less the 13.5v. I even tried shift from D to N while crusing and same thing would happen every time - while in D voltage drops to 12.x, shift to N it momentarily goes to 14.x
I've tested the voltmeter in my Mdx, just to rule out possible issues with it and observed constant 14.x readings throughout my 40 min drive, so voltmeter is good.
I'm leading towards bad alternator, but want to check with you guys first to see if anyone has epxerienced similar issues or can think of anything else, before I splurge $300+ on a new alternator.
As always thanks guys for input.