Sterling Power BB124865 12V/24V to 48V 65A Bidirectional DC-DC Battery Charger

The Sterling Power BB124865 is the Saturn series charger for rigs and vessels that have made the move to 48V house battery systems. It takes alternator power from a 12V or 24V starting system and delivers a fully regulated, 4-stage charge to your 48V house bank at up to 13A output and 750W of continuous charging power. For builders running 48V LiFePO4 rack batteries, high-efficiency inverter systems, or e-bike style battery banks in a camper or overland build, the BB124865 is the compact, purpose-built bridge between your vehicle's starting system and your house bank.

The unit auto-detects whether your input is 12V or 24V — drawing approximately 60A from a 12V source or 30A from a 24V source — and configures itself accordingly. Like every Saturn series unit, it applies the correct charge algorithm for your battery chemistry rather than sitting at a fixed output voltage. Six preset profiles cover Lead I and II, AGM I and II, and Lithium I and II, with a low-temperature cutoff that protects lithium cells in freezing conditions. Six self-recovering protection circuits manage over-voltage, under-voltage, over-current, and over-temperature faults without manual intervention. For those running 15S Pylontech or similar batteries requiring a custom absorption voltage, the optional BBR remote allows full charge profile customization.

Bidirectional reverse charging is standard. When your 48V house bank is on charge and sits above the trigger threshold, the BB124865 automatically feeds up to 20A back to the 12V starter battery (or 10A to a 24V starter) to maintain it at a healthy 13.4V — so if solar is looking after your house bank while the rig sits, your starter is looked after too. If the starter ever gets too low to turn the engine over, Jump Start Assist mode forces the reverse charge to run for 20 minutes to get you back in action.

The BB124865 is fully parallelable with other Saturn series units for expanded output, making it a scalable foundation as your 48V system grows.

Key Specs:

• Input voltage range: 9–32V (auto-detecting 12V or 24V)
• Rated input current: ~60A (12V input) / ~30A (24V input)
• Rated output: 13A at 54.8V (~740W continuous)
• Reverse charge current: 20A to 13.4V (12V) / 10A to 26.8V (24V)
• Efficiency: 92–94%
• Dimensions: 200mm × 130mm × 56mm
• Weight: 1.0 kg
• Recommended input cable: 16mm² / 6AWG
• Recommended input fuse: 80A
• Recommended output cable: 4mm² / 12AWG
• Recommended output fuse: 20A
• Certifications: CE, UKCA, E-Mark
• Cooling: thermostatically controlled variable-speed fan
• Compatible: lead acid (AGM, gel, flooded), lithium LiFePO4

Compatible with smart/variable alternators (Euro 6/7+). Ignition feed or vibration sense activation modes. Optional BBR remote available for display monitoring, custom charge voltage adjustment, and output current limiting.