Let me preface by saying that my R56 S is about 4 1/2 years old (07) and is on the original battery.

A few days ago I noticed that when I started my car, it kind of lagged a bit. Then the other day, it lagged, started, but, the check engine and TPMS light was flashing with the exclamation mark on the tach. I checked all the tires, but everything was in spec. So I reset the TPMS system, the check engine light also went off, and went on my merry way to work. After work, the car would not start - it would click, but not turn-over. I was able to push-start the car (being a manual), and make it home. I figured the battery was dead, so went through the process of removing it. An interesting thing I found is that on the stock battery, there is an indicator light noting its condition: adequate charge (green), needs charging, or replace. So I checked the light and it was green! I went to start the car again, but it wouldn't turn over. I hooked up some jumper cables from the SO's car, and charged it for 5 minutes, and jumped it at which point, it started. Let it sit idle for 20 minutes, turned it off, and when I turned it back on, it seemed to have the lagging effect again. No issues with the TPMS this time though.

So finally, to my question...is it the battery? Should I replace it even though the indicator light shows that it's in good condiiton (green)? Or is there a possibility that it's something else? Does a failing battery cause issues with other electronic systems like the TPMS, etc? TIA for any advice.

Update: after a few hours in the garage, it's not starting again....

 

You have all the symptoms of a bad battery, change it. NAPA carries a replacement battery made for the Mini complete with the vent tube, I got it for $100 after dropping off the old battery. I had a green indicator even though the battery was dead so...

 

I agree, sounds like a bad battery. My dead battery also showed green.

 

The green light just says the charge status is good...it does not mean tye battery is good...the light can be green (acid is fully charged), but the plates in the battery may be bad...so inadquate voltage.
tye light only means the battery is "sufficently charged" for testing...it does not mean the battery is good.

 

Have it load tested at your local auto parts store. Yes it can cause other systems to act up. I noticed my A/C would be on in my truck after I started it - in the dead of winter. A few weeks later it would not start one cold morning. Had the battery load tested and it showed bad. This was in a diesel with two batteries and only 2 1/2 years old. Took it to the dealer and got a new battery under warranty. The other battery remains good at 5yrs. (Knock on wood). They are rated at 7yrs, 770 CCA. So here I had 2 identical batteries with the exact same manufacture date and service duty. Yet one died way before the other.

 

All indications of a bad battery and this is about the 100 thread on this subject. Please use the search function

 

Thanks everyone for your responses. I ended up taking the battery to Pep Boys to get tested, and it was a bad cell. Got a replacement from them, Bosch Group 47, for around $110. Battery has external vent like the stock battery.

FYI (as I've seen asked on other threads), after replacing the battery, the radio stations are kept, but the time needs to be reset. TMPS also needs to be reset. Other statistics such as avg mpg, trip range, etc are also reset.