Battery light is on
Usually means that your alternator has failed.
Check your battery connections, tight and free from corrosion, and check all battery cables. Sears used to offer free battery/charging system checks. The battery is not getting charged for some reason, and it's voltage has dropped below normal limits. Usually this is what the light means. tennisshoes is correct as well. Since the alternator charges the battery once the engine has started, if it is not charging for some reason, then the light can come on. The voltage regulator could also be at fault, which is usually in the alternator or a separate unit.
Search Ford Excursion Questions
Ford Excursion Experts