boosting the voltage of a 12V battery

[lemains]

What's the most practical/cheap method to boost the voltage of a 12V battery to let's say 40V ?

I was looking at a 12 volt to 36 volt DC/DC Converter ($154) BUT the current you can pass is only 7.5A

(http://www.powerstream.com/dcdc.htm)

I know I can get a more expensive converter (currents at +20A) but just wanted to know if there is a cheaper alternative to this.

any hints?

[redneckgearhead34]

I am not sure but I believe there is a way to run a 24v system with only one 12v alternator. I saw it on a Land Rover one time but cant remeber the spec. All I know is that he had two batteries.

So if you can get 24v then you can get 36v