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My 2016 Civic with 64k miles on it had the battery die the other day. Upon inspection, massive corrosion on the negative terminal indicating undercharging of the battery. Had the car jumped and it ran fine. Did some further testing and saw the voltage at idle was 12.8V, which made me assume the alternator was bad. A shop I took it too also came to this conclusion, had the battery tested and it holds charge perfectly fine now that the terminal has been cleaned.

Upon even further testing, I saw that the alternator would kick up to 14.5V upon initial start and drop down to 12.8V after a minute or so, only kicking on when the headlights were turned on. Drove around normally, and with AC and radio on but not the headlights, voltage stayed around 12.3V-12.8V indicating that at times the computer would shut the alternator off completely.

Spoke a service technician and explained to them the issue and asked if this was normal behaviour as I suspected that Honda may have actually programmed the car to operate this way to "save fuel". Indeed, they confirmed this is how the computer is programmed.

However, 64k miles later did I only find out that the car has been undercharging the battery. The issues this causes over time, is the corrosion I saw built up. And alot of it. The problem the corrosion causes is that it can mess with the electrical system and cause other electrical issues and drain the battery (causing my battery to go dead quickly even though both the alternator and battery are fully functional). Undercharging also decreases the life span of the battery, which is why I have seen many people complaining that the batteries in Honda dont last. Its the not the battery at fault here. This is a design flaw and I have spoken to corporate about this issue and am trying to get them to acknowledge the issues the design causes.

I have found a remedy for now until I can have the computer reprogrammed, turning on the lights keeps the voltage at 14.5V stable so that I dont have to worry about the battery being undercharged, but it now worries me that perhaps they cheaped out on the alternator and forcing the alternator to run constantly (as it should) may burn out the voltage regulator, although it wouldnt in any normal alternator.

For those of you that have also experienced electrical issues and batteries not lasting, this is most likely the cause. The corrosion can also cause computers and sensors in the car to act up.
 

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The voltage to the battery is regulated by a Honda algorithm so as not to overly charge the battery and dry it out.. It is a normal function. If you use a Scan Guage you can monitor several systems on the car. I have noted the switching of the battery voltage on my 2005 Civic from and my 2019 Civic Sport.
Perhaps if you had noticed the build up of the corrosion on the terminal, you might have prevented the failure you experienced. Be assured the alternator is working just fine.
 

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My 2016 Civic with 64k miles on it had the battery die the other day. Upon inspection, massive corrosion on the negative terminal indicating undercharging of the battery. Had the car jumped and it ran fine. Did some further testing and saw the voltage at idle was 12.8V, which made me assume the alternator was bad. A shop I took it too also came to this conclusion, had the battery tested and it holds charge perfectly fine now that the terminal has been cleaned.

Upon even further testing, I saw that the alternator would kick up to 14.5V upon initial start and drop down to 12.8V after a minute or so, only kicking on when the headlights were turned on. Drove around normally, and with AC and radio on but not the headlights, voltage stayed around 12.3V-12.8V indicating that at times the computer would shut the alternator off completely.

Spoke a service technician and explained to them the issue and asked if this was normal behaviour as I suspected that Honda may have actually programmed the car to operate this way to "save fuel". Indeed, they confirmed this is how the computer is programmed.

However, 64k miles later did I only find out that the car has been undercharging the battery. The issues this causes over time, is the corrosion I saw built up. And alot of it. The problem the corrosion causes is that it can mess with the electrical system and cause other electrical issues and drain the battery (causing my battery to go dead quickly even though both the alternator and battery are fully functional). Undercharging also decreases the life span of the battery, which is why I have seen many people complaining that the batteries in Honda dont last. Its the not the battery at fault here. This is a design flaw and I have spoken to corporate about this issue and am trying to get them to acknowledge the issues the design causes.

I have found a remedy for now until I can have the computer reprogrammed, turning on the lights keeps the voltage at 14.5V stable so that I dont have to worry about the battery being undercharged, but it now worries me that perhaps they cheaped out on the alternator and forcing the alternator to run constantly (as it should) may burn out the voltage regulator, although it wouldnt in any normal alternator.

For those of you that have also experienced electrical issues and batteries not lasting, this is most likely the cause. The corrosion can also cause computers and sensors in the car to act up.
I'll be going on my 3rd battery in 3 years!
21504
 
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