My battery on my stick up cam it's draining even though connected to a solar panel

I have several stick'em up outdoor cams that are connected to solar panels. Twice in the last 2 weeks on different cameras I am told that I need to charge the battery. I'm not understanding why since they are hooked up to solar panels. Yesterday was sunny, but it was also very cold. This should definitely have charged the battery life through the solar panel. Has anybody else experienced this? I'm not sure if two different solar panels are defective, or if it's due to the extreme cold? Last week it was not nearly as cold and I experienced this with the different stick em up cam.