HQST 100 Watt 12 Volt Monocrystalline Solar Marine Kit 10 Amp PWM Duo Battery Charge Controller allows for charging more than one battery simultaneously. Bypass diodes minimizes performance drop due to partial shade and prevent battery discharge at night. Ideal for storage in tight spaces or crowded areas that are typically off limits for traditional glass and aluminum models. The junction box and MC4 connectors are sealed and waterproof. Can be installed without costly structural roof reinforcements.