my right rear airmatic shock goes down after 24hrs,there seem to be no leakage. what else could be the cause

It is likely your Air Spring is def. They getting a micro hole you can not see. You can pump it up and spray the air spring with soap. And you will see the bubbles. The battery light could be a that you need update for the Battery Control unit. Or corrosion at the connector for the control unit. Or one of your two Battery's are def.