2011 6.7 Battery light on
 

2011 6.7 power stroke battery light is on and engine idle is 100 to 150 rpm above normal. Batteries and alternator test good. Truck starts fine but battery light comes on about 30 seconds after start up. Any ideas?

bench test the alternator, load test the batteries individually and not connected to each other and the truck.

Do the batteries first. They are probably bad.