I use 2 of the 1700's don't have any problem with them fitting the box... . the new ones have a metal cover around the outside..... I took this off as it was siliconed in place and they fit the box... (barely) ... these are so strong, I was able to use only 1 battery in the winter time here in Salt Lake City..... so unless you want only 1 battery, the 2150 is too much waste of battery and money... . you don't need 2 of those..... 2, 1700's is plenty. and since these are a dry cel, they are better than even the red top or anything else... .