I would suggest you to change the alternator with a new Zen alternator, however you will have to get the pulley changed. It is a direct fit and no major mods are required to fit. Zen alternator comes with about 50Amps of capacity, compared to the M800's stock 35Amps. If you have ICE, 100/90 bulbs, central locking etc then better to switch to the Zen alternator, if your car is fully stock with no add ons the M800 alternator should be good.
M800 alternator should cost about 3500/- here in Bangalore, the Zen part costs 4350/- approx.
Here is a link to my thread and Varun's thread as well where we have done some mods to the stock set up (mine is yet to get fixed, he succeeded using the Swift alternator). http://www.theautomotiveindia.com/fo...ploaded-2.html Varun's Mega DIY on alternator
- this answers most of our queries on alternator issues and solutions.
Stock dynamo of M800 - 35Amps
Zen alternator - 50Amps
Old WagonR VXi - 60Amps
Swift (Petrol) - 70 or 75Amps
First thing is to change the alternator then jump start the car, ensure that there is enough distilled water in the battery, let the car idle for about 5 - 7 mins then drive it. If the car doesn't start again then its an issue of battery, so get the battery charged once instead of direct replacement.
All the best.