I have a battery tender 12v 750 mA. The tender is several years old. I use it for a battery that I keep out of one of my vehicles I hardly drive. When I first connect the tender to the battery the light is a solid red. The light stays red for the longest time. So I disconnect the tender and reconnect it, the light blinks green and eventually goes to solid green. The fact I have to disconnect and reconnect it so it's starts blinking is concerning me that it doesn't start blinking and eventually turns solid green by itself. Is that a indication the tender is defective?