Two different MR1100-100NAS units will stop charging and end up with a dead battery

Guys,

I've been through two of these units now at a remote site that I need to use one of these for some security cameras I have and both of the units I have had for whatever reason will just eventually stop charging and power themselves off when the battery finally is exhausted.  I have to pull the power supply from it and plug it back in to get the unit to start charging again.  Does anyone know of a way I can stop this behavior and have a reliable internet solution for my cabin?.. please??

Thanks in advance.  PS. I have thought about putting a timer on the charger to turn the power off each day for an hour and let it run on battery for that long to see if that doesn't keep it alive.  Looking for ideas or solutions to this.  I didn't see anything in the configuration for a charging setting.