Alternator chargers put every ounce of power to good use. While on the water, they take your alternator's excess power and redistribute it to your trolling batteries. You get an extra boost, and better battery life. Charge-on-the-fly: After the boat's alternator has fully charged the starting battery, this technology will reroute the alternator power to the trolling motor batteries. Battery Protection: extends battery life by protecting your battery from frequent deep discharges. LED Indicator Lights: Inform of charge stage, maintenance mode status, error notifications and full charge. Waterproof Construction: All on-board chargers are built to be waterproof, shock-resistant and vibration-resistant. 3-Year Warranty: All battery chargers come with a full 3-year replacement warranty.