GRX-3000 Midtronics Battery Diagnostic Station 6 & 12 Volt Midtronics GRX-3000 Battery Diagnostic Station. Easy-to-use scalable solution designed to support full-service battery management programs. Fast, accurate and reliable, the GRX can determine, often in less than five minutes, the difference between a recoverable battery and one that is not. Midtronics is recognized as the world leader in battery management technology. Using patented Conductance Technology, we create innovative battery testing, monitoring, and diagnostic charging solutions for a wide range of battery applications, including vehicle starting batteries, standby or backup power, and motive power.