The rain sensor stopped working, then wind became erratic. I then noticed a gradual decline in battery voltage over several months (see figure). Today the unit went offline. Suggestions?
Can you let us know your Station ID so that we can look at your data?
There is some charging but clearly not in level with solar radiation.
Time to open a ticket with support that will help you out. Not much more we can do here. Clearly a hardware problem.
BTW, that is the serial number of your Tempest device. The Station ID can be found as described here.