Maximum power point tracking (MPPT): The Renogy MPPT solar charge controller ensures that every drop of the available power is flushed out of your modules and used for storage. Tracking efficiency reaches 99% and conversion efficiency reaches 98%. Automatic detection: The intelligent controller can automatically detect 12 V/24 V DC system voltages (lithium battery should be adjusted manually). The LED indicators show solar charging and battery operation information, customizable parameters and error codes. 4-stage safe charging: Renogy 20Ah charge controller has 4-stage charging (most, increase, hover and rectification) of lead-acid batteries and 2-stage charging (bulk and increase) for lithium batteries as well as lithium reactivation. Full system protection: the self-diagnosis function can assess and protect your system from reverse polarity, overcharging, over-discharge, overload, short circuit and reverse current Remote monitoring: The RS232 communication port allows the Renogy Rover to communicate with the Renogy BT-1 Bluetooth module, which allows you to monitor the status and productivity of your panels via the Renogy DC Home app.