wen i start the car 1st thing in mornin it is really slow to turn over and wen i have heatin on, or rear window de mister on or lights on the revs drop. Does this mean batt is on its way out?its bin doin it for some time.
turn on the headlights on tickover, increase the revs and note if the lights go brighter, if they do it shows the alternator is working.(rough test).If the lights go dimmer ,could be a slipping belt. Have a feel at the battery leads to see if they are wam. If so there is a poor connection. Don't forget, in cold weather all engines are harder to turn over. A booster charge will not hurt
Batteries usualy last about 6 years, sometimes a bigger diesel one can last a lot longer, (record I personaly know of is 9 years+ on a HDi Picasso)
It's condition can be confirmed with a cheap hydrometer
