Well, I have a new problem with the Nissan. It's been snowed in,
and with temps near zero, I figured even if I dug it out, I would
probably just drain the battery trying to get it to start.

    Yesterday, after work, I dug the car out and tried to start it.
Temp about 14F. It *did* start, after the symptoms describe in
the "cold start" post. So, I let it idle for about 15 minutes to
warm up, with the heater on max and rear defogger.

    When I drove it, I noticed the dash lights seemed a little dim.
I drove it about a mile, tried to keep RPMs up to charge the battery.

    I got to the shopping center and was pulling into the parking
lot when...it died. Engine stopped, warning lights came on. Car
would not start, even when I shut all electrical off. I had to
push it to a parking spot.

    After sitting for a few minutes trying to figure out a course of
action, I turned the key. It fired right up like nothing had
happened. I revved the engine and thought it over. I shut it off.
I restarted it with no problem. So, I got my groceries, came out
and started the car again, no problem. About two blocks later, I
stopped for a stop sign. Oops, car is dead. Would not restart,
just "click click". A passing motorist gave me a jump, and I
tried to drive home without stopping. Didn't make it; trying to
push through an intersection at low speed car stalled again and
would not start. However, I was at the top of a hill, so I pushed
it through, coasted and bump-started. No problem.

    At this point, the car started losing power while driving at
15-20 MPH. I found out that if I turned the headlights off, the
car recovered power *instantly*. So I drove the last miles home
turning the lights on and off to keep the car going while I ran
every stop sign. I slammed into the driveway, cursed the car
liberally, and brought the groceries inside.

    So. What is wrong? I'm not sure. I know the guy I bought the car
from had electrical problems in boston last year. He had a garage
install a new battery and alternator (Nov '06. When I got the
car, I installed a new battery tray and hold down, cleaned  the
battery and added a little distilled water, cleaned the terminals
and clamps and sprayed with anti-corrosive. I switched that
battery for another one I had purchased  in Feb of '07 when I ran
it down trying to start the car in the last cold spell.

    I also checked the alt connections this summer while working on
the car, and they visually looked good. I noticed the starter
connector looked corroded, but it looked had to get at so  I
didn't clean it, which would be my usual "new-to-me" drill.

    After removing the battery tonight after work, I noticed the
negative cable is green and corroded between the lug and the
insulation. This looks like a "single point of failure" to me so
I am going to rehab/replace it tomorrow. I have read many posts
about bad grounds in Nissans.

    I'm thinking maybe it's a "perfect storm" problem-cold temps,
battery discharge, heavy alternator demand. I realized later that
letting it idle with the heaters on probably didn't do it any favors.

    Any specific advice from anybody?