Ford F-150 battery light

Going to call this one as a bad ground...corroded 1/0 battery cable as it leads to ground....Battery is older than five causing the alternator to work overtime to supply a battery that is reluctant to take a charge...yes, get a New battery, wirebrush the main Ground connection...fuel, ignition and the ECU all use this ground connection...kinda messes it up because the starter motor is always asking for 300 amps through this connection, yet the ECU perhaps uses 1.5 mA~ if your battery is NEW and Fresh would say tighten the belt or replace the tensioner and arm and idler bearing (in a kit)~

Thanks for your answer Judge_Roy. What are the chances that it is the alternator itself? The battery is about six years old, but it is one of those Optimax batteries (AGM) and I think its life expectancy is longer than a traditional battery.

You could test the output of the alternator to see if it is performing okay...Noise is the main concern...if it is worn out will be noisy~ 12.5- 15.0 volts is what the regulator should be putting out~

oops 13.5 to 17 volts running...my bad~~~

Could your alternator belt be slipping some upon acceleration?

I have a brand new alternator and mine is doing same thing so I'm going to agree with the battery diagnosis