Sterling Power BB1224120 12V/24V to 24V 120A Bidirectional DC-DC Battery Charger

The Sterling Power BB1224120 is the Saturn series solution for rigs and vessels running a 24V house battery bank off a 12V or 24V starting system. It takes alternator power from your 12V starter battery — or a 24V input source — and delivers a fully regulated, 4-stage charge to your 24V house bank at up to 58A output and 1,700W of continuous charging power. For overlanders, expedition vehicles, and marine installs that have made the move to 24V house systems for efficiency and cable savings, this is the charger that bridges the two worlds cleanly.

The BB1224120 auto-detects whether your input is 12V or 24V and configures itself accordingly — no manual switching or wiring changes required. 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 — set it once and it handles bulk, absorption, and float autonomously. A low-temperature cutoff protects lithium cells in freezing conditions, and six self-recovering protection circuits manage over-voltage, under-voltage, over-current, and over-temperature faults without manual intervention. We recommend pairing this unit with an alternator rated at least 20% above the 120A input demand to protect your charging system under sustained load.

Bidirectional reverse charging is standard. When your 24V house bank climbs above 26.4V (27.0V on lithium profiles), the BB1224120 automatically feeds up to 50A back to the 12V starter battery 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 BB1224120 is fully parallelable with other Saturn series units for expanded output, and supports the optional BBR remote for live monitoring, custom charge profile programming, and output current limiting from anywhere in the vehicle.

Key Specs:

• Input voltage range: 9–16V (12V) / 18–32V (24V) — auto-detecting
• Rated input current: 120A (12V) / 60A (24V)
• Rated output: 58A at 28.41V (~1,540W continuous)
• Reverse charge current: 50A to 13.4V (12V input) / 25A to 26.6V (24V input)
• Efficiency: 92–94%
• Dimensions: 270mm × 130mm × 73mm
• Weight: 1.8 kg
• Recommended input cable: 35mm² / 2AWG
• Recommended input fuse: 150A
• Recommended output cable: 16mm² / 6AWG
• Recommended output fuse: 80A
• 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.