Battery warning light will come on after starting but goes out once the battery is being charged (IF its being charged).
Use a hydrometer to check the battery's state of charge.
Even a brand new battery will not be able to turn the engine over after a few starts, if it is not being recharged.
Check alternator connections (multiplug with a wire clip to retain it).
Check drive belt tension - if this is too slack, the alternator will not be driven at correct speed.
Check battery connections not corroded or loose .
JD
April 2008