What is the use of V_Batt connector

[Tom]

No the BAT pin is only a voltage sensor.

From a second point of view it is better not to use the 6V6:
There is one IC which uses the 5V supply: PWM level shifting from 3V3 to 5V.

So: sorry, but better not do it

[magellan]

No Problem, I'll use a regulator to bring the 6.6 down to 5V.

Thanks,

Olivier