2010 Honda Fit electrical issue

I have a 2010 Honda Fit that has recently been having an electrical issue that I am having a difficult time locating. A couple of weeks ago I was driving home at night and started having issues that would seem to indicate the battery was dying - headlights going dim, power steering going out, cabin lights flickering, etc. Took it to an auto parts shop and had them test the battery/alternator. The battery was about 4 years old and tested bad as expected, so I went ahead and replaced it. The alternator tested fine. 2 weeks later I got home from a work trip where my car had been sitting at the airport for about 4 days. I got on the highway to drive home and about 15 minutes into the drive the same symptoms started again, but this time the car completely died. I had it towed back to my house and checked the battery the next morning, sure enough it was drained. I was able to recharge the battery, then I ran several tests for the alternator and checked for a parasitic draw. These tests seemed to indicate no issue with the alternator and no parasitic draw. I am not entirely sure where to look as the car was running fine for 2 weeks, including a 5 hour round trip drive to go camping this past weekend with no issue or indication that anything had been excessively draining the battery. It’s also odd to me that the car would have enough charge to start up after leaving it at the airport but then be completely drained after driving it for about 15 minutes. After recharging it, I was able to drive it around to run some errands with no issues, and checking the battery again afterwards indicated it was fully charged. At this point I’m thinking that there may be a loose ground connection somewhere that is maybe coming undone when driving at highway speeds, although I’m not sure why it would drive without issues when driving around town. Obviously this isn’t something I can safely try to replicate, am I’m not entirely sure how to pinpoint a faulty ground connection. Is there anything else I could be overlooking that might be causing this?

How much is the voltage measured at the battery with the engine running at 2000 rpm?

If the serpentine belt and tensioner are allowing the alternator to slip, might contribute.

Sounds like you need more alternator testing. The alternator is likely controlled by the engine control computer. If there is a problem with that signal, a good alternator would not charge the battery because it isn’t being directed to.

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I just checked again this morning, battery with the car off is reading 12.80V, and turned on reved to 2k rpms holds at 14.75V.

Hello, thanks for the feedback. I don’t believe the serpentine belt is the issue as I don’t hear any squealing noises from the car even in higher rmps, and visually the belt does not appear to have any excessive wear on it.
I’ll do some reading up on the ECM. Would an issue like this tend to cause a check engine light to come on? When this issue occurred, there was no check engine lights on before the issue happened. I started seeing the headlights dim, the Charging System Indicator light (little battery icon) on the dash came on and then shortly after that the lights for power steering, airbags, abs, etc started coming on. I’m wondering if maybe there’s a bad VRM on the alternator that’s causing some issue when driving at slightly higher rpms on the highway, although I’m not entirely sure how to attempt to replicate the issue safely.

That information tells you that the battery is not being charged. A scan tool should allow you to record real time data to capture the event while monitoring a few inputs that should cause that to happen.

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I’m thinking what happened is that when I left the car sitting at the airport for a few days the charge dropped on the battery just enough for it to start, but the alternator was working too hard to charge the battery back up and overheated. Is there some sort of safety mechanism that would cause the alternator to shut itself off while driving, thus causing the battery to drain shortly afterwards? I’m thinking I’ll have to leave the car sitting for another few days and check the battery to see if its drained again. I did check to see if there was a parasitic drain, and it didn’t look like there was one. I’ll run those checks again today to double check.

If not done already, check the cables at the battery terminals for corrosion, it sometimes builds up under the insulation at the terminal ends… just incase…

Then there is likely nothing wrong with the alternator. One other test, with engine running, at idle this time, put headlights on, high beams, and check voltage.

That sort of problem is possible. Battery has enough juice to crank and start the engine, but problem with charging system leaves the battery uncharged, not enough charge left to keep the engine running. The ignition system itself requires quite a bit of current to keep the spark plugs firing. You may have an alternator that tests ok, but is intermittently failing. Alternators use brushes and slip rings, and those can wear out, & fail intermittently at first, often temperature related. Does your Fit have an in-dash volt meter? If so, suggest to monitor the voltae as you drive. With engine running it should be in the 13.5 - 15.5 volt range. I expect you’ll discover it is sometimes in the 12.6 volts or less range w/engine running.

I don’t have an in-dash voltmeter but I can probably find a way to get some longer leads on my voltmeter and just attach them to the battery and drive around the neighborhood. I’ll give that a shot next. Thank you!

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A decent scanner will be able to show you life data with the voltage shown…

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