3 stage voltage converter

[mndless]

I am new to working with circuits.... and I find myself over my head on this project...

I am working on emergency radio communications box... In the box will be a 24V lithium Ion battery pack... but the radio requires a constant voltage of 13.8v +/- 10%

There are 3 levels of current demand from the radio...

1) idle - 450 mA
2) max audio only - 1A
3) transmitting - 10A

So, the circuit needs to sence the current demand and adjust the resistance to allow for a relatively constant voltage.

The input voltage could vary... between 18, 24 or 36 volts... but I can deal with that with 3 seperate independant circuits, once I understand the basic approach...

So... is there a simple approach to how this could be accomplished?

Any suggestions to point me in the right direction would be greatly appreciated...

Thanks in advance!!!

 

[crutschow]

For maximum battery life, your best choice is a switching regulator to generate the 13.8V. They generally have 80-90% efficiency. Dropping the voltage through a resistor or a linear regulator will give you only about 57% efficiency and you would be wasting over 100W (which would have to be dissipated in some manner) when transmitting.

A Google search should turn up many manufacturers that build such units. I don't recommend trying to build one yourself unless you are quite familiar with electronics.

 

[Hero999]

A switcher can supply a constant 13.8V over from 18V to 36V input.

Don't use a linear, if you do, you might as well use a cheaper 12V lead acid battery which will last as long as the expensive Li-ion battery runing a linear.

 

[mndless]

Well ok then... save me some time and hair pulling

Thanks