488 battery tender won't "stick"

clean the contacts on both car and plug. Dirt or other material can get stuck there, and interfere with the magnetic connection.

 

Also,

Make sure you have the correct maintainer.

Li Ion battery maintainers ( Pista ) are reverse polarity of say a 488 maintainer, so it will not accidently " stick " and short out the system.

Otherwise, do as Jordan mentioned, make sure the contacts are clean.

Steve

 

This is the Lithium tender and snap magnetic connector.