Thunder helps take you places you??ve never been before, making adventure more affordable and accessible for 4WD enthusiasts. Designed for the working adventurer, Thunder products have been tested and developed to handle anything you can throw at them without breaking the bank. The Thunder Battery Monitor is an easy to use battery monitor that shows monitor time to empty, battery percentage, current draw, current inwards, and wattage usage. This 12V battery monitor is sophisticated and is designed to work with most 12 Volt Gel, Lead Acid, Lithium, Lithium Ion phosphate and Calcium batteries.