Been having this issue for about 2 weeks now and trying to pinpoint the issue. Main issue is that the battery isn't charging. I was seeing 13.6V but nothing higher. And it would dip down to 11V and slowly keep going down until it hits 9V and all the electronics start freaking out. During all this time the battery idiot light never comes on. Ultimately it sets a throttle pedal fault code and I'm not able to accelerate until I restart the car again. Now I don't see any more than 12V, and generally it hovers around 11.6V and it will keep going down.

Wondering if anyone has run into a faulty alternator that provides enough power to keep the car going but not charge the battery? Doesn't really make sense to me how this is happening when battery voltage is down to 9V.

I eliminated the power steering pump since I pulled the fuse and still doesn't charge. I'm going to try disconnecting the starter and seeing if that works.

Any ideas would be appreciated. Tired of push starting my car lol

 

My guess is the alternator is very weak...making voltage, but not enough amps...but the battery maybe toast..likely is now even if it was not from sitting deeply discharged....

 

Thanks for your thoughts zippy. I never seen an alternator do that which is why I'm so puzzled over this. It's usually working or not, not somewhere in between haha

I'm feeling lazy, maybe I'll just throw an alternator at it lol

 

The exact same thing happened to my boyfriend's S in July. It just slowly started dying for a month before it stopped charging all together. It was the alternator.

 

If a diode has gone bad, the voltage will read ok, but the output will be much less...

 

I just had that happen on my motorcycle recently - the voltage looked fine, but the battery wouldn't charge. Turns out it was one (or more) of the diodes in the voltage regulator/rectifier that had failed. Thankfully, the R/R is separate from the alternator on my bike, so I only had to replace the R/R. On your MINI, it's all one unit.

 

Alternator voltage should be above 14 volts. But not over 14.5. It could be the alternator. Or it could even be a bad battery. And a battery that measures OK with a volt meter may still be bad. Voltage is not the only indicator of battery health. If it was, you could hook up 8 AA batteries in series and start and run your car with them. (Obviously, you can't make that work.)

The first thing I'd do is make sure your battery is fully charged and then do a load test on it. And make sure whoever does it uses a good old-fashioned load tester that puts a real load on the battery. NOT one of those new electronic "load testers" you see at Pep Boys, Kragens, O'Reilly's, etc. Those can NOT provide you with accurate results.

Then, if the battery checks out OK, reinstall it and start the car. The alternator should be supplying the battery with 14 volts or better. If it's not, replace it. But make sure your battery is good before doing this.

 

I just put an alternator in and still not charging. The battery is only a few weeks old, but it has been drained almost completely before. I know the battery is good, and it holds charge since I can start the car with it once its charged.

Am at bit of a loss at this point on what it could be now. I also had pepboys test the brand new alternator before I put it in so I can rule out failure of the new alt.

Any ideas?

 

The alternator has a built in regulator....
So it sounds like something is draing thr bat...
And noises...ps pump, any lights that might be on?
If the altnator spins and works power is getting made .....so something is consuming it...

 

Check your fuses?

 

Ok, so checked the voltage at the alternator this morning. I'm seeing 14.2V, so the alt is working properly. I also have the power steering disconnected(took the 100A fuse out) so that isn't the issue. I'm going to try to remove the starter and see if that might be it. Only other thing that's connected directly to the battery besides the alt.

Measured the voltage drop between the B+ on the alt and the B+ in the engine bay(the terminal next to the airbox). I'm seeing a loss of 5V. Anyone know what this cable is connected to? I'd think it'd be connected directly to the battery and the starter, but need a confirmation of sorts, can't find anything in the wiring diagrams.

Thanks again for your help, hopefully I can get this narrowed down today. It's getting too cold to ride my moto around everywhere even in CA lol

 

Problem Solved! Ended up being that the nut holding the battery cable on the starter solenoid got loose. Lots of pit marks and discoloration so its been arcing which was causing all the weird issues.

Cleaned up all the contacts and tightened her up, and good to go. What was interesting is that the alternator doesn't have a direct line to the battery. It uses the starter as a junction, which wasn't clear in the wiring diagrams.

Hopefully this will be helpful to someone in the future.

Thank you again for the help

 

Thanks for posting the resolution to your problem! I guess using the starter as the junction for joining the alternator and battery makes sense - you definitely want the battery to have a direct connection to the starter, and simply running the alternator to the starter as well means that you don't need a second long wire run from the alternator to the battery.