1. Introduction
This manual provides essential information for the safe and effective use of your Cartrend Unitec 77947 Professional Battery Maintenance Device. Please read these instructions carefully before operating the device and retain them for future reference. This device is designed to maintain the charge of 12-volt vehicle batteries, ensuring they remain in optimal condition and ready for use.
2. Safety Instructions
WARNING: Failure to follow these safety instructions may result in electric shock, fire, or serious injury.
- Always ensure the device is disconnected from the power supply before making or breaking connections to the battery.
- Wear appropriate eye protection and protective clothing when working with batteries.
- Do not expose the device to rain or excessive moisture.
- Ensure adequate ventilation when charging batteries, as they can emit explosive gases.
- Keep out of reach of children.
- Do not use the device if the cables or housing are damaged.
- Connect the positive (red) clamp to the positive (+) battery terminal and the negative (black) clamp to the negative (-) battery terminal.
3. Package Contents
Verify that all components are present in the package:
- Cartrend Unitec 77947 Battery Maintenance Unit
- Battery Clamps (Red for positive, Black for negative)
- Power Adapter with European Plug

Image: An overview of the main components included: the battery maintenance unit, battery clamps (red and black), and the power adapter.

Image: Another view of the battery maintenance device components, showing the power adapter and the main unit with connected clamps.
4. Product Overview
The Cartrend Unitec 77947 is a professional battery maintenance device designed to keep your 12V vehicle batteries optimally charged. It is compatible with various battery types and features intelligent charging to prevent overcharging and self-discharge.
Key Features:
- Suitable for all 12V battery types (Lead/Acid, GEL, AGM).
- Maximum charging current: 500 mA.
- Designed for batteries with capacities up to 120 Ah.
- Prevents self-discharge, ensuring the battery is always ready.
- Permanent monitoring of the charge status.
- Insulated and protective charging terminals for safety.

Image: The Cartrend Unitec 77947 battery maintenance device with its technical specifications, highlighting its compatibility with various battery types and charging current.

Image: Illustrating the device's electrical specifications: 12V DC output and 500mA charging current.
5. Setup
Follow these steps to correctly set up your battery maintenance device:
- Prepare the Battery: Ensure the vehicle is turned off and the ignition is switched off. Locate the vehicle's 12V battery.
- Connect Positive Clamp: Connect the RED positive (+) clamp to the positive (+) terminal of the battery. Ensure a secure connection.

Image: A hand connecting the red positive clamp of the device to the positive terminal of a car battery.
- Connect Negative Clamp: Connect the BLACK negative (-) clamp to the negative (-) terminal of the battery. Ensure a secure connection.

Image: A hand connecting the black negative clamp of the device to the negative terminal of a car battery.
- Connect Power Adapter: Plug the power adapter into the main battery maintenance unit.

Image: A hand connecting the power adapter to the main unit of the battery maintenance device.
- Connect to Mains Power: Plug the power adapter into a suitable 230V AC wall outlet.

Image: A hand plugging the power adapter into a power strip, indicating the final step of connecting the device to a power source.
6. Operating Instructions
Once properly connected, the Cartrend Unitec 77947 device will automatically begin its maintenance cycle. It features intelligent charging and continuous monitoring.
- Automatic Operation: The device will detect the battery's charge status and automatically initiate the appropriate charging or maintenance mode.
- Status Indicators: The device is equipped with indicator lights (e.g., red for charging, green for fully charged/maintenance mode) to show its current status. Refer to the device itself for specific light indications.
- Continuous Monitoring: The device continuously monitors the battery's charge level, preventing both overcharging and self-discharge. This ensures the battery remains at an optimal charge, keeping your engine ready to start at all times.

Image: The battery maintenance device connected to a car battery, with indicator lights showing its operational status.
7. Maintenance
To ensure the longevity and proper functioning of your device:
- Cleaning: Disconnect the device from both the battery and mains power before cleaning. Wipe the exterior with a soft, dry cloth. Do not use abrasive cleaners or solvents.
- Storage: Store the device in a cool, dry place when not in use. Ensure cables are not kinked or damaged.
- Inspection: Periodically inspect the cables, clamps, and housing for any signs of wear or damage. Do not use a damaged device.
8. Troubleshooting
If you encounter issues with your device, refer to the following common problems and solutions:
| Problem | Possible Cause | Solution |
|---|---|---|
| Device not turning on / No indicator lights | No power from mains outlet; Loose power connection; Damaged power adapter. | Check mains power supply; Ensure power adapter is securely plugged in; Inspect power adapter for damage. |
| Battery not charging / Red light not on | Incorrect battery connection; Battery is already fully charged; Severely discharged or faulty battery. | Verify correct polarity (+ to +, - to -) and secure clamp connections; If battery is full, device will enter maintenance mode (green light); Have battery tested by a professional. |
| Green light on immediately after connection | Battery is already fully charged. | This is normal. The device is in maintenance mode. |
If the problem persists after attempting these solutions, please contact customer support.
9. Specifications
| Feature | Specification |
|---|---|
| Brand | Cartrend |
| Model | 77947 |
| Manufacturer | Unitec |
| Input Voltage | 230V AC (via power adapter) |
| Output Voltage | 12V DC |
| Max. Charging Current | 500 mA |
| Battery Capacity Range | Up to 120 Ah |
| Compatible Battery Types | Lead/Acid, GEL, AGM |
| Item Weight | 370 g |
| Shipping Dimensions | 16.7 x 10.8 x 6.1 cm |
10. Warranty and Support
For warranty information and customer support, please refer to the documentation provided with your purchase or contact the retailer/manufacturer directly. Keep your proof of purchase for warranty claims.
Manufacturer: Unitec
Model: 77947



