The radio memory only draws a tiny amount, some people hook up an
ordinary 9 volt alkaline battery to keep all the memory things alive
when the system is "off" The 9 volts is enough & one battery should
last
you the season.

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Question: If the 9-volt battery should "last a season" wouldn't there
be almost no chance that the radio memory was drawing down the primary
12-volt battery in a week?