Amazon.com: dkplnt 12V 24V to 56V 10A 560W DC to DC Charge 48V Battery Converter for Flooded, Gel, AGM, and Lithium, Using Multi-Stage Charging in RVs, Vehicles, Boats, Yachts with Acc Ignition :
Battery Charger 12V into 48V
Car Li-ion Battery Charger 1.5A DC 12V to 36V Converter - China DC 12V to 36V Converter, DC DC Converter 12V 48V | Made-in-China.com