Can anyone verify whether or not their 718 has variable charging voltage during normal driving? My 2018 718 base model always shows 14.8 volts on the multi-display, while my 981 would vary, usual from low 13s to high 14s, depending on driving conditions. Thanks!
Battery charging voltage question
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I am guessing there is a program where battery charging voltage varies with battery temperature, total electrical load, and, especially, state of battery charge. In any case, a thirteen something voltage or higher means the alternator is both carrying the total electrical load and putting energy back into the battery. A higher voltage means energy is being driven into the battery at a higher rate. 14.8 volts would be appropriate for a battery with less than an almost full charge and/or high electrical load. If the battery is at or very near full charge, it is appropriate for the charging voltage to be lower and that could explain the low 13 something voltage you observed.
To fill out the story, my car gave me a "low battery" warning, and was charging at 14.8 all the time, which makes sense if the battery is charging up from a low state. Dealer told me that it is normal to always be at 14.8. Dealer subsequently determined that a prior dealer who had installed new battery for the previous owner failed to re-set the computer to reflect that battery was new, so they re-set it. When I got the car back yesterday, I was seeing 14.2 right after start-up and before getting under way; after I started driving, it would increase to 14.6, and stay there, even when idling at a stoplight. I had the battery checked by a third-party, and checked good (although shows as bad by my CTEK).
So, I'm wondering what others are seeing as normal driving voltage variances--does your voltage drop down into the 12s or 13s during normal operation, or does it always stay in the 14s? As I said, my 981 would drop down--it was supposedly for fuel economy (clutching/slacking the alternator would put less drag on belt/engine). As a side note, when I put the key in accessory position, I have seen as low as 12.2, which is obviously not good, but also doesn't seem to be accurate--the lowest I have measured with a voltmeter is 12.48. I'm starting to wonder if maybe there is an issue with the voltage regulator/charging system, although the car apparently passed all the diagnostics.
So, I'm wondering what others are seeing as normal driving voltage variances--does your voltage drop down into the 12s or 13s during normal operation, or does it always stay in the 14s? As I said, my 981 would drop down--it was supposedly for fuel economy (clutching/slacking the alternator would put less drag on belt/engine). As a side note, when I put the key in accessory position, I have seen as low as 12.2, which is obviously not good, but also doesn't seem to be accurate--the lowest I have measured with a voltmeter is 12.48. I'm starting to wonder if maybe there is an issue with the voltage regulator/charging system, although the car apparently passed all the diagnostics.
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Your comment about the battery testing as bad by the Ctek, are you sure you did the test correctly?
Your Voltmeter, is it accurate (?), not all of them are. A reading of 12.2v is possible when a battery is being subjected to a very high current draw...
As for the CTEK test... connect (off power) and press mode button for battery. I've used it on other cars just fine.
The 12.2 V reading was on the cars MDF, not with a meter. The lowest I have seen with my meter (Fluke 16) is 12.48 V, but I've also metered 12.66 V right after driving--seems to drop off pretty quick when the door is opened.
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Sounds right for the Ctek test I have MUS4.3
The Fluke should be accurate enough
12.66v is good to, I am wondering if your car has some unusual current draw... did I miss the age of the battery?
Battery was replaced by previous owner at dealer (under warranty) last February. I thought it was a bit unusual, but the car was only driven 6,000 miles in the first 18 months, so it is possible that it went bad from sitting. But... based on the voltages I am seeing, I am also wondering about current draw. Dealer checked and says okay. If I do get another low battery warning, I will do my own current draw test (meter in-line, pull fuses). In the meantime, I was hoping to confirm what others are seeing for normal driving voltages--if people report 12s or 13s as standard, then it would indicate to me that I do have a problem for sure; if people report that they see mid to high 14s after they start driving, with no variability, then I may be okay, and worrying for nothing.Sounds right for the Ctek test I have MUS4.3
The Fluke should be accurate enough
12.66v is good to, I am wondering if your car has some unusual current draw... did I miss the age of the battery?
FYI... for anyone reading this who doesn't know this, you can add voltage to the multi-function display: vehicle>settings>display>vehicle menu (using lower right stalk)
Can you give me a range? How low when driving easy, or idling at a stoplight?
Okay, my earlier comment about opening the door got me to thinking about something I had read with my 981 about the electronics staying active for 30 minutes after the door is opened/closed. So, I hard-wired my CTEK lead to the battery terminals and let the car sit for an hour, then metered off the lead... 12.66V. I don't know enough about electricity to understand the interplay between draw and voltage, but it appears that the draw from the electronics is enough to drop the measurable voltage from 12.66 to 12.48. So, that was a red herring, as probably is the low voltage on the MFD, since I can only see that with the key in the accessory position, which draws even more--hence the 12..2 and 12.3 readings on the MFD.
I'd still be interested in hearing what voltages folks are seeing during normal driving.
I'd still be interested in hearing what voltages folks are seeing during normal driving.
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Your display will show voltage? How do you get that? I did a cursory scan through the display settings yesterday and didn't find anything to show voltage.
vehicle>settings>display>vehicle menu (using lower right stalk)
You get up to four lines, I believe, so you can add the available items to whatever line you want, as I recall. You can also leave the lines blank.
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Thanks. I did that, didn't see voltage. Must try again
I just checked mine... the full list is available for each line. Battery voltage is the very first item. If there is an existing item that is further down the list, you will need to scroll up to see the battery voltage item.
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Mine almost always seems to charge at 14.8. Occasionally, if I am doing a long drive, it will drop down to 14.2 or 14.3, but 15 to 20 minute drives around town always show 14.8. After I stop and turn off the engine, the reading is usually 12.8. I'm using the voltage reading off of my radar detector, which seems very accurate. I can go a few days without driving the car. If I go 3 days for example, the readout will show 12.0 prior at start up, then go right to 14.8. Three days is the exception, usually I never go more than skipping a day, and occasionally 2 days.
Thanks, very helpful!
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My 981 always showed in the 14v range when running, car is gone now, but I do remember this.
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I found the voltage readout. It showed 14.9v while I was sitting in traffic, lights on, engine idling in Sport mode.
I wish there were one more line in the display. I'd like to see turbo boost pressure, water temperature, oil temperature, and voltage. I suppose I don't really need to see boost pressure but it such a cool thing to see!
I wish there were one more line in the display. I'd like to see turbo boost pressure, water temperature, oil temperature, and voltage. I suppose I don't really need to see boost pressure but it such a cool thing to see!
Not sure what else you have on the lines, but mine allows 4 lines, and those are the things I have on display, in that order even.
Ha Jim! Like you and @couver I have the same line items. The boost pressure IS fun and 90 percent of time its boosting, I'm not looking at it. Before I knew how quick it was, I asked the service manager if it was functioning!
It was of course. The error was between the seat and the steering wheel.1 - 20 of 21 Posts
