Ok, I've been fighting with my evo for at least 2 weeks, maybe 3. Here's the background story.

When Captain America: Civil War came out, my friends and I saw it at the drive in. My car stayed on the whole time for the audio to be broadcasted to my stereo. After the movie, car came on just fine.

Few weeks later, my car popped up the charging system service required on my dashboard. Ok, charged the battery. Went to 100%, put it on. Still does the same thing. Charging system service required. Just to make sure, I get it charging at autozone overnight. I left the battery off for 2 days to see if it will discharge on itself. It didn't. Still at 100%.

So, I kept driving it to monitor any changes. At first, the charging system service required pops up when I drive over 4200rpm on 4th gear, and when I switch to 5th, it goes away. Then every day, that rpm trigger gets lower and lower until 4 days ago the dash went crazy. It popped up every single service on the dash: 4wd, awe, etc. It even went to the point that I'm driving 40mph and the speedometer is at 0mph. The dash just goes limp, but everything else is fine. Engine isn't sputtering or anything.

So, I went back to autozone to get the battery charhed up again. Lefy it for another 2 days to see if it will discharge. First thing I did after the 2 day wait and installed the battery is go to autozone to get both the battery and alternator tested. Both passed. I also did the voltmeter test. My battery when the engine is off read 12.7, and when the engine is on, it's at 14.3v.

I checked all the fuses under the hood specifically the 7.5a alternator fuse. Still good.

Everything is OK, at least the machine on autozone said it's ok. So, what is going on? Is my alternator busted?

I might as well add that my fuel pump is hardwired to the battery. And this is an optima yellow top.

Any ideas?

 

Update: bought a new battery. Still the same thing. So, I'm going to guess it's the alternator.

 

If you're reading 14.3V with the engine running, then your alternator is working perfectly fine. It doesn't seem likely, but it could be a faulty warning system. Or possibly a connection came loose and the system thinks you're losing power when you hit bumps in the road. I would start checking main ground connections as well as wiring connections behind the gauges before just buying an alternator.

 

now that i've been thinking about it. it could also be the belt loosening at the rpm. but the thing is, as the battery discharges, the rpm where the notification comes on changes as well. i charged the battery and the RPM is back up to 4200 when it turns on

 

So a battery with more charge would make the rpm higher when the light comes on? The thing is, the battery shouldn't affect the car at all when it's running.

When the engine is running, the battery acts like a capacitor instead of a power source. It's there to handle short bursts of power if the alternator can't react fast enough. Like right when you turn on the headlights or A/C, but a second or two later the alternator will adjust and take the load off the battery.

So if the car is just sitting there idling or driving constant, you could technically drive without a battery even hooked up to the car. So I find it hard to imagine that a battery issue is giving you a light on the dash. I would look more into the alternator, check output voltage, check the belt quality and tension, check grounding points, etc.

Your battery won't just magically drain from sitting there, but if the alternator is broken, your battery won't last 30-40 mins of driving with minimal radio usage.

 

Based on your posts, I'm going to go with an intermittent alternator failure. If the belt is tight, it's probably time to just swap out the alternator.

 

OR is the regulator letting the alt output exceed the max voltage?


Can you monitor actual voltage as you drive (through OBDII port or via a meter hooked up)?


A battery with a dying/shorted cell could cause this as well...