I have been experiencing a slow draining of the battery for the past 1-2 months wherein the vehicle will be fine and suddenly the vehicle will not start.
First thought was the battery, as the vehicle has about 90000 on it. I could have tested it, but didn't; just bought another one thinking it would save the trouble soon enough if it wasn't the battery. On installing the battery, I checked for the usual: lights left on, doors left open, etc. But there was nothing out of the ordinary.
Two weeks later, the new battery drained. I charged up the old one swapped it in. One week later, that one was drained.
Determined now that it was not the battery, I searched high and low for some good tests. I did a ground test (all less than 2-1ohm), point to point resistance check(all 1-2ohm), parasitic draw test (30mA after entering sleep mode), and charging voltage test. Everything looked satisfactory. The only thing that I noticed was, if I left the nominal voltage charging test run, for minutes, I would slowly watch the voltage creep down. After twenty minutes I was seeing 13.8V after starting at 14.3V (measured across the battery terminals). I ran out of time to swap out the battery on my multimeter (thinking this might be the culprit), so it could just be that. But, I'm curious. Does a slow fall of the charging voltage (across the battery terminals) indicate an alternator problem? Belt tensioner problem? Looking for thoughts on this slow decline in charging voltage across the battery to determine where to dig into next. I didn't see how low it could go, but if the community thinks it's worth a shot, I'll do it (even if it means an hour to find it).
The vehicle: '08 Nissan Rogue, AWD. 90k miles.
The problem has reoccurred once in the past month (10/15), after charging up the battery, I took it to Auto Zone for an alternator check where they informed me that everything was ok. I'm starting to wonder about belt tensioner. Perhaps the belt is slipping past the alternator and the charging voltage is dropping.
