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Attached is a schematic that demonstrates the proper method for back emf surpression. Is D1 necessary, and will D1 alone surpress the back emf if D2 is not installed? I think it will not due to the reverse politary of the induced voltage at disconnect.
Thanks,
TAP

 

D1 will prevent the battery from being used in reverse polarity and drop about 1/2 a volt while it is in operation.

D2 is arranged properly for back EMF protection, but this simple schematic has nothing that needs protecting.

 

To add to what Kermit said, relays are generally turned on/off with transistors. D2 is correct, and will protect said transistors.