The smarTROLL Clip-on Battery Pack provides 80 hours of continuous field use to the smarTROLL MP Handheld and smarTROLL RDO Handheld through four replaceable 1.5 V (AA) batteries. The Battery Pack also wirelessly communicates with the user's iPhone, iPod, or iPad device using Bluetooth Low Energy radio technology. Probe data is sent directly to the iSitu App. The Battery Pack is capable of measuring air temperature and barometric pressure for real-time water level and dissolved oxygen data compensation.