Renogy's DC to DC MPPT on-board Battery Charger is designed to give you options! This multi-stage, multi-input battery charger can charge a service battery from a starting battery linked to an alternator or by utilizing solar panels connected directly to the unit. While your vehicle's alternator prioritizes your starting battery, this unit will allow your solar system to charge your service battery first! It's the smart way to keep yourself fully charged and off-grid longer! And with multi-stage charging and multi-chemistry functionality, Renogy's DC to DC MPPT Charger has you covered whether you're using Flooded, Gel, AGM, or Lithium batteries. With RJ45 communication port featured, you can unlock monitoring features exclusively using the BT-2 Bluetooth Module and Renogy DC Home App, control and monitor the device remotely through your phone in real time.