how to change lower linit for'charge bit?

I just bought this ENVY-DV6 7206 product.
i read about 'terminate charge bit' when battery charge is between 94% to 100%.
I want to change that lower limit to 75 or 80%.
Is there any recommended or safe lower limit for this?
Also inform me if there is any other or better way to stop battery charging while ac charger is plugged in like DELL BATTERY METER where we manually can stop battery charging.
Thank You