1. Introduction
This manual provides essential information for the safe and efficient operation of your Mastervolt ChargeMaster 12/70-3 battery charger. The ChargeMaster 12/70-3 is designed to provide fast and complete charging for your batteries using advanced 3-Step+ charging technology. It includes a memory function to prevent overcharging, even with an unstable power supply. This model offers 12 VDC/70 amp output and accepts 90-265 VAC, 50/60Hz input. For enhanced functionality, an optional remote display and MasterBus compatibility are available.
2. Safety Information
Please read all safety instructions carefully before installing or operating the ChargeMaster 12/70-3. Failure to follow these instructions may result in electric shock, fire, serious injury, or death.
- Always disconnect power before making or breaking electrical connections.
- Ensure proper ventilation around the charger to prevent overheating.
- Do not expose the charger to water or excessive moisture.
- Only qualified personnel should perform installation and maintenance.
- Use appropriate personal protective equipment (PPE) when working with electrical systems.
- Verify input voltage and frequency match the charger's specifications.
3. Setup and Installation
The Mastervolt ChargeMaster 12/70-3 comes with essential components for installation, including a battery temperature sensor, the ChargeMaster battery charger itself, documentation, and installation hardware. Proper installation is crucial for optimal performance and safety.
3.1 Product Overview

Figure 1: Front view of the Mastervolt ChargeMaster 12/70-3 battery charger, showing the display and overall design.
3.2 Electrical Connections
Ensure all connections are secure and correctly polarized. Refer to the wiring diagrams in the included documentation for detailed instructions. The charger supports 90-265 VAC input at 50/60Hz.

Figure 2: Rear view of the ChargeMaster 12/70-3, illustrating the AC input and DC output terminal connections. Note the clearly labeled positive and negative terminals for battery connections.

Figure 3: Close-up view of the internal wiring connections within the ChargeMaster 12/70-3, showing the robust terminal blocks and cable management for secure and reliable power distribution.
4. Operating Instructions
The ChargeMaster 12/70-3 is designed for user-friendly operation, automatically managing the charging process once connected and powered on.
4.1 Charging Technology
This charger utilizes advanced 3-Step+ charging technology to ensure fast, complete, and safe charging of your batteries. This process optimizes battery life and performance.
4.2 Memory Function
A key feature of the ChargeMaster 12/70-3 is its integrated memory function. This function prevents overcharging of batteries, even in situations where the incoming power supply is unstable or intermittent.
4.3 Optional Features
For enhanced monitoring and control, the charger is compatible with an optional remote display. It also supports MasterBus, Mastervolt's decentralized digital communication system, allowing for integration into a larger power system.
5. Maintenance
Regular maintenance ensures the longevity and reliable operation of your ChargeMaster 12/70-3.
- Keep the charger clean and free from dust and debris.
- Periodically check all electrical connections for tightness and corrosion.
- Ensure ventilation openings are not obstructed.
- Inspect cables for any signs of wear or damage.
6. Troubleshooting
If you encounter issues with your ChargeMaster 12/70-3, refer to the following basic troubleshooting steps. For more complex problems, consult the full documentation or contact Mastervolt support.
- Charger not powering on: Check the AC input power supply and ensure all connections are secure. Verify the circuit breaker has not tripped.
- Batteries not charging: Confirm battery connections are correct and secure. Check battery voltage; if extremely low, a different charging method might be needed initially.
- Overheating: Ensure adequate ventilation around the unit. Clear any obstructions from air vents.
7. Specifications
| Feature | Detail |
|---|---|
| Model Name | ChargeMaster 12/70-3 |
| Part Number | 44010700 |
| Brand | Mastervolt |
| Input Voltage | 90-265 VAC |
| Input Frequency | 50/60 Hz |
| Output Voltage | 12 VDC |
| Output Current | 70 Amps |
| Charging Technology | 3-Step+ |
| Item Weight | 15.4 Pounds (approx. 7 kg) |
| Item Dimensions (LxWxH) | 20 x 14 x 9 inches (approx. 50.8 x 35.6 x 22.9 cm) |
| Included Components | Battery temperature sensor, ChargeMaster battery charger, Documentation, Installation hardware |
| Manufacturer | Seawide Marine Distribution, Inc. |
| Date First Available | February 24, 2012 |
8. Warranty and Support
Warranty information for the Mastervolt ChargeMaster 12/70-3 is typically provided with your purchase documentation. Please refer to these documents for details regarding warranty coverage, terms, and conditions.
For technical support, service, or further inquiries, please visit the official Mastervolt website or contact their authorized service centers. Contact information can usually be found in the documentation included with your product or on the manufacturer's website.
Manufacturer: Seawide Marine Distribution, Inc.
Brand: Mastervolt
For the most up-to-date support resources, please visit: www.mastervolt.com





