This is probably a dumb one, but here goes: I just bought a used fish finder (Humminbird) but I'm not sure what kind of battery to use. The seller didn't know because it had belonged to his grandfather who recently passed away. I think it would take a 12 volt but I'm not sure since this is my first fish finder. Where would I buy a battery that would be appropriate. I'm old school and never used anything but trial and error. Mostly error so I thought I'd give this electronics thing a try. Thanks in advance for your help. NamVet66
