I have a 2005 Mazda 6i (L3 engine, Auto-trans), purchased new in 2005. Recently we have been having an issue with the battery light coming on intermittently. The battery is about two years old (7-year battery),. The alternator was just replaced (bad bearings) this month (Dec. 2014). We have taken it to three different automotive parts stores and had them check the battery, alternator, and charging system, everything checks out fine. I am an ex-mechanic and have personally checked the battery, alternator, and charging system outputs (all within range). I have checked for parasitic draws (none that I can find). We have also noticed that at idle the rpm seems to fluctuate between 600 - 900 rpm. We have also had the car die on us when we stopped several times. We can turn the key off and start it right up again, and no battery light will be on. Several miles later it will come on again. We can do the same thing when the battery light comes on; turn the key off and restart the car, then no battery light for several miles again. I have also checked for any current or pending codes, and there are none. I am at a loss, I know I am missing something, but cannot figure out what. This is driving me crazy, I need some help. Where else do I need to look, what am I missing? Can someone please point me in the right direction? I will check out all possibilities and post back here the results.