my 2003 alt will barely move after jumping mechanic said alternator was bad on 2003 Nissan Altima

the problem has occurred twice had it towed to a shop who got it started and ran fine after that he said the alternator was bad had it checked but was told it was ok had to jump it again it barely moves when in drive

by in Long Branch, NJ on May 30, 2013
2 answers 4 comments
ANSWER by on May 30, 2013
How old is the battery? Has it been tested? No bad cell(s)?
COMMENT by on May 30, 2013
its good its only 3 months old
COMMENT by on May 30, 2013
How was it tested? Even new batteries can be defective!
COMMENT by on May 30, 2013
alternator and charging system was tested on a machine
COMMENT by on May 30, 2013
Starting wityh a fully charged battery(assume 12.5 volts) turn on the high beam headlights (engine off), and let it sit for twenty minutes and re-test the battery.Might show a bad cell.
ANSWER by on May 30, 2013
AGREE WITH ZIPTIE