The alternate source typically is an inverter

Single Drawer Freezer w/ Ice Maker

Louvers 9 Size 5"Wx 6"L

Size Open 1-1/2"  x 1-1/2"   Description  Surface Type

Available in Brass

Battery Isolator: Argo FET 100-2 Connectors The alternate source typically isSimilarly to Argodiode battery isolators, Argofet isolators allow simultaneous charging of two or more batteries from one alternator (or a single output battery charger), without connecting the batteries together. In contrast with Argodiode battery isolators, Argofet isolators have virtually no voltage loss. Voltage drop is less than 0,02 Volt at low current and averages 0,1 Volt at higher currents.