It's a mess. Using a lower wattage charger (apple or other brand) won't charge a Macbook. If the battery is flat, it won't do anything to it, no sound, no light

It's a mess. Using a lower wattage charger (apple or other brand) won't charge a Macbook. If the battery is flat, it won't do anything to it, no sound, no light, macbook looking dead. But if the Macbook is booted up, the same charger can provide enough power to keep it charged forever.