Indeed, the HP CASL Framework is a package needed by the Battery utility app. It gives the battery certain access to sensors, information and provides to the end user various statistics about it. If you don't have the package installed, the battery's utility won't work as it should.
The best place to download the file is from the download page provided by HP for your product. Access the support page, input your model number and then check the downloads. In most of the cases, that package is installed through the Windows Update section, therefore check the Windows Update info.