Sterling Power BB4812 48V to 12V DC-DC Converter and Battery Charger | 550W

The Sterling Power BB4812 is a dual-purpose device that solves a problem common to any build running a 48V house battery bank: how do you power your 12V loads cleanly and efficiently without a separate 12V battery system? The BB4812 does two things in one compact unit — it converts 48V DC input to a stable, regulated 12V DC output at 40A and 550W, and it doubles as a full 4-stage multi-chemistry battery charger for a 12V battery or bank if one is part of your install.

As a converter, the BB4812 takes any input between 39–60V and delivers a rock-solid 13.8V output at up to 40A straight off the shelf — no configuration required. That's enough to run a 12V compressor fridge, 12V pumps, LED lighting, USB-C laptop and phone chargers, or a 12V inverter up to around 500W, all directly from your 48V house bank with no 12V battery needed as a buffer. The unit's high internal capacitance makes the output exceptionally stable — it behaves like a properly regulated power supply, not a variable voltage source.

As a charger, it operates exactly like the rest of the Saturn series — current limiting, 4-stage charge profile, and adjustable output voltage to match your 12V battery chemistry. If your install includes a 12V battery alongside the converter function, the BB4812 keeps it properly conditioned without overcharging. Both functions are available simultaneously — the converter and charger capabilities work together, not as a switchable mode.

At 98% efficiency and just 1.0 kg, the BB4812 is one of the most capable and compact 48V-to-12V solutions available for overland builds, expedition campers, and marine installs that have moved to 48V as their primary house voltage.

Key Specs:

• Input voltage range: 39–60V DC
• Rated output: 40A at 13.8V (~550W continuous)
• Default output voltage: 13.8V (adjustable)
• Efficiency: 98%
• Quiescent current: 1mA
• Operating temp: -20°C to 60°C
• Dimensions: 165mm × 130mm × 56mm
• Weight: 1.0 kg
• Certifications: CE, UKCA
• Cooling: thermostatically controlled variable-speed fan
• Self-recovering protections: under-voltage, input over-voltage, output over-voltage, over-current, over-temperature

No 12V battery required for converter operation. Optional 12V battery can be added — the BB4812 is fully current limiting and will charge it as part of normal operation.