Coolidor question

Hey all, my brother has fallen down the slope pretty hard and had to upgrade to a coolidor that he is having problems with. He got a 70 quart and is using a pound of beads which is twice that is recommended.
He is mainly keeping boxes in it but he can't keep the humidity down, it is staying between 70-75%. He keeps the coolidor at his shop which is not heated and the temperature drops down into the 40's. He has put the beads in almost dry to help with the high levels. He has heard that with cold temperatures the humidity level will go up in a confined space like a cooler. Does anyone know if this is true and if so what would you recommend to try to reduce the humidity. If he opens the cooler for a couple of hours it does drop but then by the next morning it's back to the 70's. We're in the DC area and the humidity is fairly low now so not sure what to recommend to him. So any help would be appreciated.

MarioF