I would suggest an external battery!
Everybody with Cell Cams that are going to be unattended goes that route sooner or later, may as well do it from the start and save the headache. We found you need a 6v 12ah SLA battery to run the cam for 30 days without a solar charger, and with reserve left that the battery isn't depleted or shuts down the cam. The bigger ah battery the better and the longer it will run. I run my HCO and Covert cams on real time and get about 30 days or more between battery change with the 6v 12ah SLA battery. When I fill up the feeders I swap Batteries so It's one operation and I don't have to go back for a month. I could go with a bigger SLA battery but I find the 6v 12ah SLA battery gets me through one feeding cycle without the expense of solar charging and the price of the larger SLA batteries. I would also have a problem with solar charging because of tree cover.
I also only use 4 AA batteries for the internal cam Batteries because I found that they get depleted right along with the external battery, with about the same voltage left in them. I swap them out as well when I swap out the external so everything stays fresh.
I have only 2 Coverts one 2015 FW upgraded to 2016 for App portal use and one 2016 that I'm just going to get ready to update FW that is supposed to correct some issues. GFORCE have you performed the FW upgrade on Covert? If so, can you also keep us up to date on how it's operating?
I have my 2015 in the woods with the FW update with 12v 7ah battery level 7 since around 17 July 2016 and only roughly 50 - 100 photo's. With deer movement very low since the heat and humidity put its grasp on East Coast. I'm hoping that when I go to PA end of the month the deer movement will be better.
What I my do is put the 2015 upgraded FW camera in sunny location with the Covert Solar panel that has the battery inside the solar panel. Of course Covert no longer sells that solar panel for whatever reason but before I upgraded to the current FW the panel always kept the camera operating with no problems. I might put the Wildgame Innovations 12v 7ah battery connected to it with solar panel and put the 2016 upgraded FW in the woods with no sun connected to 6v 12 amp battery.