Introducing the XTM DC-DC Charger, the perfect solution for keeping your second battery charged while you're in the great outdoors. It has a 40A capacity and can be used with either DC or solar so can be set up to suit your needs. The DC-DC charger is compatible with Lead-acid, AGM, Gel, Calcium and LiON (LiFeP04) batteries. It features 6 charging steps for optimal charging and to protect your battery. The 6 stages are; Qualification: The charger will test the battery for faults. If the battery voltage is lower than 2V then it can't be charged. If it is higher than 2V it will move on to stage 2. Recondition: After the charger identifies the battery voltage, it will start to charge the battery with a small current to activate the battery and improve battery charging efficiency. Absorption: With the increase of battery voltage, the charging current to the battery will then reduce to avoid over charging. Full and Analysis: When the battery voltage level reaches a fully charged state, the charging current will drop to 0. The charger will then shut off all output and measure the voltage drop over 1 minute before entering the next charging stage. Maintenance: The charger will continue sending small pulse currents to the battery keeping the voltage on about 13.5V. If the voltage drops below 13V, stages 1-5 will repeat.