2001 BMW 540i Base 8 Cyl 4.4L
Will a car run ok with a failing battery?
'98 Subaru forester
When a battery wears out it puts upon the alternator to continue to run all electrical systems by itself, Generally if all your operating is the engine it will run OK, it's not until you start turning on accessories like A/C , heater blower, headlights, etc. you will find the alternator not equipped to handle all power needs and this is where the battery comes in. So OK is a question of opinion and not a positive supposition.