Cen-Tech 55 Amp Battery Charger 6678 Manual

The Cen-Tech 55 Amp Battery Charger (Model 6678) is a versatile automotive battery charger designed for 12V lead-acid batteries. It features a 55-amp engine start function, 10-amp fast charge, 2-amp trickle charge, automatic voltage detection, reverse polarity protection, digital display with charge status indicators, and a built-in cooling fan. Suitable for cars, trucks, motorcycles, boats, and other vehicles. Below are key sections for safety, features, installation, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Safety Instructions 3. Installation & Setup 4. Specifications 5. Controls and Indicators 6. Charging Procedures 7. Engine Start Function 8. Maintenance & Storage 9. Regulatory Information 10. Troubleshooting

Features at a Glance

Key components: Charger unit with digital display, Charge rate selector switch, Engine Start button, Clamp cables (red/black), AC power cord, Cooling fan, Reverse polarity alarm.

Feature	Description
55A Engine Start	Provides high current for starting engines with dead batteries
10A Fast Charge	Standard charging for typical automotive batteries
2A Trickle Charge	Maintenance charging for motorcycles, small batteries
Automatic Voltage Detection	Detects 6V/12V batteries automatically
Reverse Polarity Protection	Alarm sounds if clamps are connected incorrectly
Digital Display	Shows voltage, charge status, and error codes
Charge Status LEDs	Indicates charging, fully charged, and fault conditions
Cooling Fan	Prevents overheating during high-current charging
Heavy-Duty Clamps	Insulated copper clamps for secure connection
Overcharge Protection	Automatically switches to float mode when full

Safety Instructions

Read all instructions before use. Failure to follow may cause injury or damage.

Use only with 12V lead-acid batteries. Do not charge dry-cell or lithium batteries.
Work in well-ventilated area. Batteries produce explosive gases.
Wear eye protection and gloves. Battery acid can cause severe burns.
Disconnect AC power before connecting/disconnecting battery clamps.
Connect positive (red) to positive terminal first, then negative (black) to chassis ground.
Keep charger dry. Do not expose to rain or moisture.

WARNING! Risk of explosion. Do not smoke or create sparks near battery. Keep children away.

Installation & Setup

Unpack and inspect contents. Ensure all parts are present and undamaged.

Place charger on stable, dry surface near battery but away from engine components.
Plug AC power cord into grounded 120V outlet. Do not use extension cords.
Set charge rate selector to OFF position before connecting to battery.
Connect clamps: Red to positive (+) terminal, black to negative (-) terminal or chassis ground.
Verify reverse polarity alarm does not sound. If alarm sounds, disconnect immediately and correct connections.

CAUTION! Ensure battery terminals are clean and free of corrosion before connecting.

Specifications

Model: 6678
Input Voltage: 120V AC, 60Hz
Output: 12V DC
Charge Rates: 55A (Engine Start), 10A (Fast), 2A (Trickle)
Battery Compatibility: 12V lead-acid (Wet, AGM, Gel)
Display: Digital LCD (voltage, charge status)
Protections: Reverse polarity, overcharge, short circuit, thermal
Cable Length: 6-foot power cord, 4-foot clamp cables
Dimensions: 10.2" x 7.1" x 5.9"
Weight: 8.8 lbs

Controls and Indicators

Front Panel: Digital display, Charge rate selector (OFF/2A/10A/55A), Engine Start button, Status LEDs.

Display Indicators: Battery voltage (xx.x V), Charging (flashing), Fully Charged (solid), Fault (Err code).

LED Status: Red (charging), Green (fully charged), Yellow (fault).

Charge Rate Selector: OFF – Disconnects power; 2A – Trickle charge for maintenance; 10A – Standard fast charge; 55A – Engine start (use only for starting, not continuous charging).

Engine Start Button: Press and hold for up to 3 seconds to deliver 55A boost while attempting to start vehicle.

Charging Procedures

Follow these steps for safe and effective battery charging.

Ensure charger is OFF and unplugged from AC power.
Connect clamps to battery terminals (red to +, black to -).
Plug charger into AC outlet. Digital display will light up.
Select charge rate: 2A for maintenance, 10A for standard charging.
Charger will automatically detect voltage and begin charging. Red LED will flash.
Monitor display: Voltage will rise as battery charges. When fully charged, green LED will light solid.
To disconnect: Turn selector to OFF, unplug AC cord, remove black clamp first, then red clamp.

Tip: For deeply discharged batteries, use 10A setting. Charging time varies by battery capacity.

Engine Start Function

Use only when battery has sufficient charge to crank engine but needs assistance.

Connect clamps as in normal charging procedure.
Set charge rate selector to 55A position.
Turn ignition key to ON position (do not start yet).
Press and hold Engine Start button for up to 3 seconds while attempting to start vehicle.
If engine does not start within 3 seconds, release button and wait 30 seconds before retrying.
After successful start, immediately set selector to OFF and disconnect clamps.

WARNING! Do not use 55A setting for continuous charging. Overheating may occur. Limit engine start attempts to three tries with cooling periods between.

Maintenance & Storage

Unplug and clean after each use. Store in dry, cool location.

Wipe exterior with dry cloth. Do not use liquids or solvents.
Inspect cables and clamps for damage before each use.
Clean battery clamps with baking soda solution if corroded.
Store charger in original box or protective case.
Do not store near chemicals or extreme temperatures.

CAUTION! Do not disassemble charger. No user-serviceable parts inside.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits for residential use. UL Listed. Copyright © 2025 Cen-Tech; trademarks of Harbor Freight Tools. For support, visit www.harborfreight.com or contact 1-800-444-3353.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No display/power	AC power not connected	Check outlet; ensure power cord is fully plugged in.
Reverse polarity alarm sounds	Clamps connected incorrectly	Disconnect immediately; reconnect red to +, black to -.
Battery not charging	Poor connection; dead battery	Clean terminals; ensure clamps have good contact. Battery may be sulfated.
Charger overheats	High ambient temp; blocked vents	Move to cooler area; ensure fan vents are clear.
Display shows "Err"	Fault detected	Turn selector to OFF, disconnect, wait 5 minutes, then retry.
Engine start not working	Battery too weak; bad connections	Charge battery first with 10A setting; check all connections.

Reset: Unplug from AC power for 5 minutes to reset internal electronics.

Service: 1-800-444-3353; www.harborfreight.com