Guys thank you for your input, what do you think about this little circuit?
From:
http://www.radio-electronics.com/info/data/semicond/zener-voltage-reference-diodes/applications-circuits.phpA Zener diode circuit that uses a series pass transistor. A simple circuit is shown below and here the transistor is used as an emitter follower.
Zener diode circuit for a simple regulated power supply
When utilizing this circuit, the current required from the Zener resistor potential diver should be calculated. This is the emitter current from the transistor divided by the gain.
When choosing the Zener diode voltage, it should be remembered that the emitter voltage will be lower than the Zener voltage by the amount of the base-emitter voltage - 0.6 volts for a silicon transistor.
To be honest I am having trouble wrapping my head around a Zener diode and if they will drain power after the battery drops at or below the Zener voltage and it is no longer allowing current to flow in reverse to ground.
If my thinking is correct then this little circuit should work to drain off the excess voltage and stop draining when voltage is at or below Zener voltage. Am I correct or out in left field?
Sleemanj it is my understanding that the buck converter creates a lot of emi when switching off, is this true about the emi as that is the problem I have now with the bec.