As I promised the cutter will be connectable to a home solar kit. That means that you want to connect it to a 12V or 24V DC power source. Unfortunately lead batteries vary their voltage depending on their stored energy. A full battery has a voltage of approx. 13V, an empty battery has a voltage of about 10V.

I use two DC/DC converters to get the voltage down to 5V for operating the raspberry PI.

You can use any DC/DC breakout board. An Example is this one: https://www.sparkfun.com/products/9370

I purchased these: http://www.ebay.com/itm/5Pcs-Output-1-23V-30V-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Supply-/321476590827?hash=item4ad97f7ceb which are based on the LM2596.