possible battery backup?

[salty joe]

I just read the very well written plan by chipmunkkofdoo m2 for a battery backup and it inspired this idea.
Since I have a DC pump that runs well on 12V as well as 20V, could I skip the inverter and not switch from DC to AC then back to DC using diodes? So during a power outage, the battery would be directly connected to the DC pump.

 

[salty joe]

I probably got the wiring wrong in the attachment but my question is, Is it possible to use diode in a similar fashion?