I ran a search on this forum and online and I've come across people with what sounds like this problem, however it's usually the battery or the alternator. I've had both tested twice and they're both fine. So the problem:

When I start my car after it's been sitting overnight, the battery light comes on, and the idle sort of chokes at lower rpm, before bouncing back again. After the car's warmed up and driven about a block or two, the battery light goes away and the car drives perfectly. If I shut the car off and go shopping for 30 minutes the battery light doesn't come back on. The car has to totally cool off again. I'm wondering what this could be if it isn't the battery or the alternator. I'm not getting any check engine light, so I can't look up a code. I have a long trip coming up and I'm worried that I'll be stranded. What could be going on? Is it actually the alternator, and it's not showing up since I'm getting it checked at the auto parts store once it's warmed up?

 

Sounds to me like the idle is dropping too low which is then causing the alternator to not charge which is then causing the light to come on.

Normal for an idle that is too low, but need to figure out why the idle is dropping so low.

How many miles on car? When was last spark plug change and valve adjustment.

Generally speaking, the vast majority of issues with a first gen Fit are traceable to spark plugs, coils, or lack of valve adjustment.

 

Thank you for the quick response. The car has 230k miles. I had a valve adjustment about 6 months ago, I've put on around 15k miles since then. The spark plugs were replaced last year with oem plugs. The car has run like new since the valve adjustment, until now. Prior to the adjustment I was getting a check engine light for a misfire which has gone away since it's been done. It would also idle very roughly when cold, and when at a stop light. Now the car sort of acts like it's going to die when it's first started, but only slightly, like there's not enough power, and the rpm sort of blimps. If I turn the wipers on during this time they move very slowly. Once the car is warmed up everything is perfect, and I don't have any issues even when at a stop light at low rpm. The engine idles perfectly.

Prior to the valve adjustment I was getting a check engine light, now it's just the battery light with no code.

 

Good information!

I would try an idle relearn by leaving the battery disconnected over night. Once re-connected, let it idle till warm and then take it for a drive.

It's a long shot, but free to try.

 

I've seen this symptom before.

Your serpentine belt could be slipping (not adequately spinning the alternator.) When the engine warms up, it actually 'grows' (gets larger) as the aluminum expands, and the belt will again drive the alternator.

Replace the serpentine belt and see if that fixes your issue.

 

Can someone put voltmeter on battery terminals and check the voltage when battery light is on? Sounds like worn out alternator brushes

 

Battery light is usually an alternator issue. Confirm voltage when car is started versus when ignition is off for 10 minutes. Is some rare cases, the battery is actually bad, and is acting like a dampner to lower the total current. Check voltage first.

 

Resurrecting this dead thread because I'm having the exact same issue. Really strange, getting 11..5 - 12ish volts when car is first started, but voltage jumps around sometimes hitting 14.5 (where it should be). Battery light comes on and off. Sometimes it takes 10-15 minutes for everything to settle down and charging to get back to normal. If I have a bunch of accessories on, I can actually drain the battery to the point that the power steering starts to die.

What I've done:
1. Had battery and charging system load tested (battery and alternator checked out as being in good health)
2. Cleaned battery connections
3. Disconnected ELD (Honda Electrical Load Detector - varies alternator output based on load for the sake of efficiency). No change.

Anyone else had these symptoms and managed to get it resolved?

Btw, here's a quick vid for anyone who stumbles upon this thread and wants to see how to disconnect the ELD on 2007-2008 Honda Fits:

 

The OP's issue was a varying idle. If your idle is staying solid, they you probably have an issue with the voltage regulator on the alternator.

If your car is dropping idle below 650ish, then it's just turning the alternator too slow. In that case you likely need a tune up and maybe a valve adjustment if not performed in the last 60k miles.

 

Good catch, my situation is not that the idle is dropping/bouncing. The alternator, voltage regulator, and battery tested fine, so I'm on the path of crossing t's and dotting i's to make sure I'm not overlooking anything.

 

Gotcha! I'd double and triple check the ground cables.