Solar door Mount - How can I tell it is charging

Had the ring door bell Gen 2 , and purchased the solar backing plate . its in a very sunny location. The device health says it is connected  but the battery life is reducing by 1% a day  currently at 95%. Given the weather is very sunny  I would have thought the  the solar would maintain the battery life at this time of year. I can see it is connected but can't see that it is charging  the door bell has very little use  maybe once our twice a day  How can I tell it is working and not faulty ?