Sorry to take so long getting back to you.
Detailed information is available on the DC to DC Converter board made by Artesyn.
The link to their webpage about the converter is
Be sure to download the Data Sheet to get important hookup information.
It may be ordered from Mouser Electronics and their page is
The circuit board needs someone who knows electronics to solder connection wires for DC input, DC output and Voltage Control. Then the board needs to be mounted in an enclosure with several capacitors, and the voltage control potentiometer, and a small fan to provide cooling air. It is a very efficient synchronous converter which will develop little heat even at full load, but it is always a good idea to provide air flow in case environmental conditions become hot.
The data sheet tells how to connect two or more converters for current sharing in the event you desire to go beyond 40 Amperes of output current.
It is possible to build your own less sophisticated circuit which will accomplish the same conversion but it would be less efficient, from 70% to 80% tops. However, the total cost for a home built unit would be about half the price.
It would probably be best to install it under the dash rather than in the engine compartment, although the relay to control input power may be mounted in the engine compartment. Just run heavy wiring to and from for DC input and DC output to your cell wherever it is installed.