Sterling Power
Sterling Power BB1225 – 12V 25A DC-DC Battery Charger
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The Sterling Power BB1225 is a 12V-to-12V DC-DC (battery-to-battery) charger that keeps your second, or house, battery correctly charged from the vehicle's alternator while you drive. It is the heart of any dual-battery or overland power system: rated at 25A (about 345W), it suits most builds running a fridge, lighting, and device charging.
If you are new to dual-battery systems, the short version is this: a modern alternator will not properly charge a separate house battery on its own, and a lithium battery in particular needs a controlled, multi-stage charge. The BB1225 sits between the two batteries and does exactly that. Unlike a simple voltage-sensitive relay, it measures both current and voltage and steps intelligently through bulk, absorption, and float, so your battery gets a full, correct charge on every drive.
Charging Specifications
| Type | 12V → 12V battery-to-battery (DC-DC) charger, Saturn series |
|---|---|
| Input voltage range | 9–16V DC |
| Nominal output voltage | 12V DC |
| Output voltage range | 0–15V |
| Max output current | 24A at 14.41V (≈345W) |
| Max output power | ≈345W |
| Max input current | 26A at 13.68V (≈355W) |
| Efficiency | Up to 98% (95–98%, buck-boost) |
| Standby current | 5mA |
| Reverse / jump-start current | Bidirectional reverse-charge + jump-start assist (from ≥6V) – exact reverse current available on the datasheet; contact us to confirm |
| Battery profiles | 6 selectable (Lead, AGM, Lithium) + custom via optional BBR remote |
| Temperature sensor | Included – temperature compensation and 0°C lithium trip |
| Cooling | Thermostatically controlled variable-speed fan |
| Protections | Self-recovering: under-voltage, input & output over-voltage, over-current, over-temperature |
| Recommended cable / fuse | 6mm² cable / 30A fuse |
| Dimensions | 123 × 130 × 56 mm |
| Weight | 0.6 kg |
| Operating temperature | −20°C to +60°C |
| Certifications | CE, UKCA, E-marked (certificate no. 24*10R06/01*3789*00) |
| Warranty | 5-year return-to-factory |
Key Features
- 25A output (about 345W) – sized for most van, camper, and overland dual-battery builds
- Buck-boost design charges fully even when a smart alternator drops its voltage – Euro 6+ compatible
- Lithium-safe with 6 selectable battery profiles (lithium, AGM, and lead) plus custom profiles via the optional BBR remote
- Bidirectional reverse-charge and jump-start assistance back to the starter battery
- Included temperature sensor, up to 98% efficiency, and self-recovering protections
- CE / UKCA / E-marked; 5-year return-to-factory warranty
- Features named current-limiting technology
- Optional BBR remote control offers adjustable current-limit presets at 65%/85%/100% plus live voltage/current readout from the output
- Reverse-charge engages automatically once the output (lithium profile) battery exceeds approximately 13.5V, holding the input/starter battery around 13.4V
Smart Alternator / Euro-6 Ready
Three engagement modes cover any vehicle: automatic voltage sense (turns on above roughly 13.5V input), ignition-feed control (for smart / Euro-6 alternators), and vibration sense (begins charging once the internal accelerometer detects the engine running – no ignition wire required).
Installation Notes
Use a common, direct negative between the starter battery, charger, and auxiliary bank. Take the positive input from a circuit fed by the starter battery (or an Alternator Linearisation Device) – not straight off a bare alternator. Rate the charger to no more than about 80% of your alternator's output; Sterling recommends an alternator of at least 35A. Fuse both the input and the output; recommended cable is 6mm² with 30A fusing.
Presented by Overland Kitted
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