How do you cancel red battery warning light on SL350 2004

To answer you question directly: srew out the bulb. but that dos only hlep the short time, since your car will stop working soon.

i hop your question meant how to solve that issue what is causing this to light up.

Usualy this is a problem at or near the generator. The gen dos no longer produce enough electricity to run the car and the car is currently satisfying his needs from the battery, draining it.

the cause can be a defective gen, a devective regulation unit, a loose or broken cable or a bad contact. usually i would review the cables and check the gen and regulator with a voltmeter. usualy the cause pops up then.