Problem after using Battery Tender

[JPERL]

I have been keeping a battery tender attached to the battery to keep it charged since I don't use the van much. But now when I turn the engine off and remove the key I noticed that the green illumination on the stock radio LCD panel is lit, the radio is off the LCD readout is off but the green illumination only for the LCD panel remains backlit anywhere from a 1 to 10 minutes. Important to note its not the illumination that lights the buttons when you turn the headlights on.

Can damage occur from using a tender?

[trestlehed]

I do the same as you with the Battery Tender.

I haven't had any issues. My radio is fairly new though.
Did you say your radio is the stock toy van radio?
If so, maybe there is an internal failure. Might be time to consider and upgrade?

[JPERL]

Its an original stereo everything works its just parts of the illumination stays illuminated for a few minutes after the igntion key is turned to the off position. Its just the lights on the radio nothing else. does not run the battery down because the stereo lights stay lit for a few minutes.