DC-DC battery chargers
Charge your leisure or service battery from your vehicle's alternator with intelligent multi-stage charging. Ideal for marine, motorhome, and commercial vehicle applications.
Compare products
Common applications
Commercial Vehicle
24V systems are common in trucks — the 30A 24V covers most service battery needs.
Campervans & motorhomes
Rooftop solar charging while you travel — no hookup needed.
Leisure marine
Keep batteries topped up on board without running the engine or a generator.
DC-DC Chargers Specifications
| Product Name | DC-DC Charger 30A 12V | DC-DC Charger 50A 12V | DC-DC Charger 30A 24V | DC-DC Charger 100A 12V |
|---|---|---|---|---|
| Merlin Part # | 04-6002 | 04-6003 | 04-6004 | 04-6006 |
| Rating | 30A, 12V | 50A, 12V | 30A, 24V | 100A, 12V |
| DC Output | ||||
| Output Current (Maximum) | 30A | 50A | 30A | 100A |
| Output Voltage Range | ||||
| Charge | 13.5 - 15.5V | 13.5 - 15.5V | 27 - 31V | 13.5 - 15.5V |
| Float | 13 - 13.8V | 13 - 13.8V | 26 - 27.6V | 13 - 13.8V |
| Equalise | 15.5V | 15.5V | 31V | 15.5V |
| Charging Control | 5 Stages | 5 Stages | 5 Stages | 5 Stages |
| DC Output Bank | One | One | One | One |
| Efficiency | > 90% | > 90% | > 90% | > 90% |
| Battery Type Programmes | Gel, AGM, Flooded, Lithium | Gel, AGM, Flooded, Lithium | Gel, AGM, Flooded, Lithium | Gel, AGM, Flooded, Lithium |
| DC Input (Battery/ Alternator) | ||||
| DC Input Range | 10.5 - 32VDC | 10.5 - 32VDC | 10.5 - 32VDC | 10.5 - 32VDC |
| DC Input Nominal Operation | 12.8V for 12V Charging System, 25.6V for 24V Charging System | 12.8V for 12V Charging System, 25.6V for 24V Charging System | 12.8V for 12V Charging System, 25.6V for 24V Charging System | 12.8V for 12V Charging System, 25.6V for 24V Charging System |
| Engine Start Control: ON | DC Input from Battery/Alternator | DC Input from Battery/Alternator | DC Input from Battery/Alternator | DC Input from Battery/Alternator |
| Engine Start Control: OFF | DC Input from PV Input | DC Input from PV Input | DC Input from PV Input | DC Input from PV Input |
| Maximum Input Current | 30A | 30A | 30A | 30A |
| DC Input (PV Input) | ||||
| DC Input Range | 10 - 50VDC | 10 - 50VDC | 10 - 50VDC | 10 - 50VDC |
| DC Input Nominal Operation | 17.5VDC for 12V PV Panels Connected in Parallel, 35VDC for Dual 12V PV Panels Connected in Series | 17.5VDC for 12V PV Panels Connected in Parallel, 35VDC for Dual 12V PV Panels Connected in Series | 17.5VDC for 12V PV Panels Connected in Parallel, 35VDC for Dual 12V PV Panels Connected in Series | 17.5VDC for 12V PV Panels Connected in Parallel, 35VDC for Dual 12V PV Panels Connected in Series |
| MPPT Tracking Efficiency | >98% | >98% | >98% | >98% |
| DC Output Protection | ||||
| Reverse Polarity | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset |
| DC Output Short-Circuit | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset |
| Over Charge | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset | Yes (Shutdown), Auto Reset |
| Cooling | Force Air Ventilation | Force Air Ventilation | Force Air Ventilation | Force Air Ventilation |
| Display Panel | ||||
| Display | LED Display with Back Lighting | LED Display with Back Lighting | LED Display with Back Lighting | LED Display with Back Lighting |
| Digital Display | Voltage, Current, Status | Voltage, Current, Status | Voltage, Current, Status | Voltage, Current, Status |
| Enclosure | ||||
| Weight (Kg) | 1.85 | 1.85 | 1.85 | 3.23 |
| Dimensions (MM) | 242x172x74 | 242x172x74 | 242x172x74 | 356x205x97 |
DC-DC CHARGER FAQS
As a guide, choose an output current that's 20–25% of your leisure battery's Ah capacity. A 100Ah battery suits a 20–30A charger; a 200Ah bank suits a 40–50A charger.
Yes, you can use Merlin's DC-DC chargers on electric vehicles. They're a stable way of charging your additional auxiliary batteries using the onboard 12V auxiliary battery fitted as standard to the vehicle to. With a built-in MPPT, Merlin Power DC-DC chargers can also handle additional charge from solar panels.
Yes — DC-DC chargers regulate the charge profile, protecting both your alternator and the lithium battery. Do not connect a lithium battery directly to an alternator.
Yes. All Merlin DC-DC chargers are designed to work with vehicles fitted with smart alternators (variable voltage regulation), which is essential for modern vehicles.
Need Help Choosing a Battery Charger?
Our technical team can specify the right charger for your system and arrange installation anywhere in the UK.
