There is supposed to be a small stainless hex screw that threads into the underside of the big button, passes through a small hole in the top of the down tube into the powertube compartment. You push at the top end of the range boost to remove the battery. It should protrude just enough so that, when the release button is pushed in, the flat head of the bolt makes contact with your interior power tube battery, preventing it from engaging the unlatch mechanism, unless you move the powertube battery out of the way. That way the one battery lock works to secure both batteries. Unlock the main power tube battery and remove it, then push the button to free the power pack from the outer range boost mount. If the bolt is adjusted too far out in it will interfere with complete insertion of the powertube. It should be adjusted so that the power tube just clears underneath it upon insertion, clear of any contact. I think using some blue locktite thread sealant would be wise to keep the screw from either working its way in or our and remain in proper adjustment.