Does yours keep up with the battery depletion? First time I have tried one & it seems to NOT be working as I thought it would. I put a voltmeter on my feeder & it is losing 1/10 volt per day.

I've never had any problems. Are you sure your battery is good? Will it discharge on it's own if it's not connected to anything?

Battery is new. Do these chargers have a life expectancy?

With 6 volt systems the batteries do run down after extended periods with a working solar panel and fresh battery.
I have had no issues with any of my 12 volt systems. They run and run without any issues as long as the panel is providing power
and the battery holds a charge.

The solar panel might not have a blocking diode built in. Without one it can drain power from the battery at night or over long times of cloud cover or shade.
If it's a 12 volt battery, you could have a 6 volt panel hooked up to it. Check the power coming out of the panel. I bought a used feeder last year that had a 12 volt battery that was not keeping up. I found the solar panel on it was a 6 volt. I disconnected the panel until I replace either the battery or the panel to match them up correctly.
And to your last question, I don't know about life expectancy, but I do know they can go bad.

Which solar panels are you using? I've had issues with the Academy brand ones, but have boss buck now and they have worked good. I've also had more issues with 6v panels than 12v panels.

could just be defective. I used 6v batteries and solar panels for years with minimal issues. Most of my issues were factory defect right out of the box. I used wildgame innovations panels

Make sure a squirrel or rat has not chewed on your solar panel wire. Could be in a place that is hard to see and that could be your issue. I have had solar panels that go bad after 10 yrs from constant direct sun. Mine now are turning yellow and not getting the full amount of sun they used to get when they were brand new.

The wire on your charger may be reversed they are positive and negative.

With thoughts of checking the simple things first, have you measured the voltage drop over a day with the solar panel not connected to the battery?

I've found too the output of solar panels drops significantly without direct sunlight hitting them. Changes in the angle that sunlight hits a panel can also vary its output.

One of mine, 3rd year with the same battery and charger, never turned the feeder off, Academy brand. I am impressed, I did not think it would last this long.

Oh and I face the charger South, not sure if that matters.

Is the battery you are using a rechargeable battery?

Check for good contact or moisture, frayed wires or even crimped wires. replaced the wires and connectors on my when the coons started hanging on them.

Limiting factor is battery life, my panel is 10+ years old but I'm on my 3rd battery. Should be trouble free for several years, check you output in full sun, not just Voltage but actual mA output.

I use the 6 volt 19.99 panels from Academy, I just had to change my first panel after 8 years. Batteries seem to last 2 or 3 but my panels almost never fail. Really pleased with performance. I have 5 feeders running for 4 months

If you've ever played around with a solar panel with a volt meter you know it matters a lot. The angle at which you tilt it can improve performance as well.

Test the voltage output of solar panel. Is a Wildgame battery? Wildgame anything suck. We will not use their batteries. We buy all of ours at Brown's feed in Lampasas.