This is so awesome that my daughter stole mine, so I have to purchase another. Running off of the car charger, we were able to plug in, via the power plug, two tablets. A kindle, and my phone were connected via the USB. The kindle and one tablet were being used for games, one tablet was being used to browse the internet, the phone was being used as a hotspot. It kept them all fully charged. It does get a little warm, but not hot enough to be uncomfortable if you were to touch it. I just kept it where there was airflow. I have not used it connected to the battery. The clamps are not anything special, they’re pretty lightweight, but they do appear to have a decent clamp to them. The car charger piece is good and sturdy and provides a solid connection. The cable could be a little longer, but it’s adequate.