when driving the battery light will come on

i have a 2001 ford windstar with 80,000 miles when driving the battery light will come on i have hooked up a digital multimeter when light is on im getting 14.10 to 14.13 volts when i come to a stop the light goes out and sometimes the voltage will spike to 15.6 to 15.8 and then drops back to 14.10 to 14.13 it never goes below that unless im running all accesories i have cleaned all terminals and checked all connections