I'm looking for relay boards that can handle 20V/20A DC easily and can be switched with the raspberry pi. I have been googling for days but haven't found anything ready made for DC, only for AC. I want to turn on a cheap tire inflator (12V and 12Amps) with the pi and the power for the inflator comes from a power adaptor. The relays I have found are mostly found in cars and I'm not experienced enough to come up with my own solution as these types of relays require more than 5V to be switched. Can you help or provide a diagram?
if you want to high current capacity Relay for control device you can use Solid state relay
refer this link for SSR Solid State Relay
Use an N-chsnnel MOSFET to switch a 12V (car) relay. A 2N7000 is good for this.