Sterling Power BB12120 12V 120A Bidirectional DC-DC Battery Charger

The Sterling Power BB12120 is our go-to recommendation for vans and expedition campers running serious lithium battery systems. At 120A input and 110A output, it delivers the kind of charge current that can actually keep pace with high-capacity house banks and sustained off-grid loads. We typically recommend the BB12120 as a strong starting point for builds in the 200–400Ah range and above — though the right charger always depends on your alternator capacity, your loads, and how you actually use the rig.

Unlike a basic DC-DC converter sitting at a fixed voltage, the BB12120 applies a true 4-stage charge profile tailored to your battery chemistry. Six preset battery types cover Lead I and II, AGM I and II, and Lithium I and II, so the unit is delivering the correct absorption and float voltages your cells need — not a generic voltage that can shorten battery life over time. A low-temperature cutoff protects lithium cells in freezing conditions, and six self-recovering protection circuits handle over-voltage, under-voltage, over-current, and over-temperature faults without manual intervention.

Bidirectional reverse charging is standard. When your house bank climbs above 13.2V (13.5V on lithium profiles), the BB12120 automatically feeds up to 40A back to the 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 BB12120 is also fully parallelable — two units give you 240A total, or mix with other Saturn series units for fine-grained current control as your build evolves.

Key Specs:

• Input voltage range: 9–16V
• Rated input current: 120A
• Rated output: 110A at 14.41V (~1,584W continuous)
• Reverse charge current: 40A
• Efficiency: 92–94%
• Dimensions: 270mm × 130mm × 73mm
• Weight: 1.8 kg
• Recommended input cable: 35mm² / 2AWG
• Recommended input fuse: 150A
• Recommended output cable: 35mm² / 2AWG
• Recommended output fuse: 150A
• 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.