Why Circuit not outputting max voltage?

[roineust]

Hello!

I am using the following circuit, with a LiPo 3S 11.1V (which charged, outputs 12.5V), with a split from the bat, one side to a regulator, that converts to 5V towards the Arduino and rest of chip legs, that need 5V and the other split side, stays 12.5V, for the motor that is switched on/off, by the chip via the Arduino, here is the schematics (in case you can't see the link, a picture is attached) :

http://fritzing.org/projects/drive-m...l293d-sn754410

I have 2 questions, regarding this circuit:

1. Why when bat is fully charged (12.5V), still, the motor gets only about 10.5V? Is it the grade of the pot i am using? should i use a higher quality pot? What would happen, if i used instead of that 10k pot a 5k pot? How can i get the full 12.5V?

2. If i want to have this circuit without a pot, just switch the max 12.5V on/off, without changing the voltage, what should i change in the circuit?

Thanks a lot!

[pebe]

You received an answer on another forum that suggested you use a power FET.
That is the best way to go.