Schumacher SC1667 Battery Charger User Manual

The Schumacher SC1667 Manual Timer-Controlled Battery Charger is a heavy-duty 12-volt battery charger and engine starter designed for charging automotive, marine, and deep-cycle lead-acid batteries. Featuring multiple charging rates, a manual timer, engine start assistance, boost mode, and an easy-to-read ammeter, the SC1667 provides dependable charging and emergency starting support for a wide range of vehicles and equipment.

Product Overview

The Schumacher SC1667 combines battery charging and engine starting capabilities in one durable metal housing. It is intended for charging 12-volt lead-acid batteries, including:

• Standard flooded batteries
• AGM batteries
• Gel batteries
• Deep-cycle batteries

The charger is not designed for charging dry-cell household batteries or powering low-voltage systems other than starter-motor applications.

Main Functions

The SC1667 offers three primary operating modes:

Charge Mode

Used for charging automotive, marine, and deep-cycle batteries.

Boost Mode

Provides a high-rate charging boost to quickly add energy to heavily discharged batteries before starting.

Engine Start Mode

Supplies additional starting current to assist vehicles with weak or discharged batteries.

Parts and Components

The charger includes several external components designed for easy operation. The product diagram in the manual identifies the following parts:

Component	Function
Metal Case	Protects internal components
Carry Handle	Easy transport and storage
Charge Rate Selector Switch	Selects charging or starting mode
Manual Timer	Controls charging duration
Ammeter	Displays charging current
Color-Coded Battery Clamps	Connects to battery terminals
120V AC Power Plug	Connects charger to household power

Key Features

Heavy-Duty Metal Construction

The SC1667 features a durable metal housing designed for workshop, garage, and home use.

Multiple Charging Rates

The charger supports several charging levels, allowing users to match charging output to battery condition and size.

Manual Charging Timer

The built-in timer gives users full control over charging duration and prevents prolonged charging when properly monitored.

Engine Starting Assistance

The engine start function delivers additional current for cranking engines with weak batteries. It is intended for temporary starting assistance and must always be used with a battery installed.

Built-In Ammeter

The front-mounted ammeter allows users to monitor charging activity and battery condition during operation.

Important Safety Information

Battery charging involves electrical current and explosive battery gases. Always follow the safety precautions outlined in the owner’s manual.

Personal Safety Precautions

Before using the charger:

• Wear eye protection.
• Wear protective clothing.
• Remove rings, bracelets, watches, and necklaces.
• Keep fresh water and soap nearby.
• Avoid touching your eyes while working around batteries.

Battery acid can cause severe burns and requires immediate medical attention if it contacts the eyes.

Battery Safety

Always:

• Work in a well-ventilated area.
• Keep sparks and flames away from batteries.
• Never smoke near batteries.
• Keep charger clamps from touching each other.
• Never charge a frozen battery.

Lead-acid batteries generate explosive gases during normal operation.

Charger Placement Guidelines

For safe operation:

• Position the charger as far from the battery as cables allow.
• Never place the charger directly above a battery.
• Do not place batteries on top of the charger.
• Ensure adequate ventilation around the charger.

Battery gases and electrolyte can damage the charger if improperly positioned.

Understanding the Control Panel

The SC1667 uses two primary controls: the Charge Rate Selector Switch and the Timer.

Charge Rate Selector Switch

The selector switch controls operating mode.

Charge

Used for normal battery charging.

Boost

Used to quickly add charge to a severely discharged battery before starting.

Engine Start

Provides extra cranking current to help start a vehicle with a weak battery. Always use this setting with a battery connected.

Manual Timer

The timer controls charging duration.

Functions include:

• Setting charging time manually
• Preventing overcharging
• Allowing customized charging periods

Users should determine battery size and state of charge before setting the timer.

Ammeter

The ammeter shows charging current in amperes.

What the Readings Mean

• High readings indicate the battery is accepting significant charge.
• Readings gradually decrease as the battery approaches full charge.
• When current stops decreasing, the battery is typically fully charged.
• During engine cranking, the needle moves to the far right of the meter.

How to Set Up the Charger

Before first use:

1. Remove all packaging materials.
2. Remove cord wraps.
3. Fully uncoil all cables.
4. Inspect the charger for damage.
5. Verify that the power cord and clamps are in good condition.

The manual recommends fully extending and organizing cables before operation.

Connecting the Charger to a Battery

Charging a Battery Installed in a Vehicle

Negative-Ground Vehicles

Most vehicles use a negative-ground system.

1. Connect the red clamp to the positive battery terminal.
2. Connect the black clamp to the vehicle chassis or engine block away from the battery.
3. Avoid carburetors, fuel lines, and sheet metal.
4. Connect to a heavy metal frame or engine component.

Positive-Ground Vehicles

1. Connect the black clamp to the negative battery terminal.
2. Connect the red clamp to the vehicle chassis or engine block away from the battery.

Always disconnect in reverse order after charging.

Charging a Battery Outside the Vehicle

1. Verify battery polarity.
2. Connect the red clamp to the positive terminal.
3. Attach a 24-inch insulated cable to the negative terminal.
4. Connect the black clamp to the free end of the cable.
5. Stay away from the battery during the final connection.

This procedure helps reduce the risk of sparks near the battery.

Charging a Battery

Charging a Battery Installed in a Vehicle

1. Turn off all vehicle accessories.
2. Open the hood.
3. Clean battery terminals.
4. Set the timer to OFF.
5. Connect the battery clamps.
6. Plug the charger into a 120V outlet.
7. Select the desired charging rate.
8. Set the timer to the required charging time.
9. Monitor both the charger and battery throughout charging.
10. Disconnect when charging is complete.

Charging a Battery Outside a Vehicle

1. Place the battery in a ventilated location.
2. Set the timer to OFF.
3. Clean terminals.
4. Connect clamps correctly.
5. Plug in the charger.
6. Select charging rate.
7. Set timer.
8. Monitor charging progress.
9. Disconnect clamps in reverse order when finished.

Using Charge Mode

Charge Mode is intended for:

• Passenger vehicles
• Trucks
• Marine batteries
• Deep-cycle batteries

The charging process must be monitored continuously. Stop charging when the battery reaches full charge to prevent damage.

Using Boost Mode

Boost Mode quickly restores energy to:

• Heavily discharged batteries
• Large-capacity batteries

This mode is commonly used before attempting engine starting. Monitor the battery throughout the process.

Using Engine Start Mode

The Engine Start feature provides temporary starting assistance for vehicles with weak batteries.

Engine Start Procedure

1. Set the timer to OFF.
2. Connect the charger to the battery.
3. Plug the charger into a 120V outlet.
4. Turn the selector switch to Engine Start.
5. Crank the engine for up to 5 seconds.
6. If the engine does not start, wait 3 minutes.
7. Try again.

In very cold weather or when battery voltage falls below 2 volts, use Boost or Engine Start for 5 minutes before attempting to crank the engine.

Important Engine Start Notes

• Never use Engine Start without a battery installed.
• If the battery has been charged and the vehicle still will not start, have the battery tested.
• Repeated unsuccessful starting attempts may indicate vehicle problems unrelated to the battery.

Fan Operation

The internal cooling fan operates whenever the timer is active.

Keep the charger vents clear of obstructions to ensure proper airflow and cooling. Fan operation during charging is normal.

Calculating Charge Time

The charger uses manual timing, so estimating charging duration is important.

Charge Time Formula

1. Determine battery amp-hour (Ah) rating.
2. Determine percentage of charge required.
3. Multiply Ah rating by required charge percentage.
4. Divide by charging rate.
5. Multiply by 1.25.
6. Add one additional hour for deep-cycle batteries.

Example:

100 Ah × 50% × 1.25 ÷ 20A = approximately 3.1 hours

This calculation provides an estimated charging duration.

Typical Charging Times

Cars and Trucks

Battery Rating	10A	20A	40A	50A
200–315 CCA	2¼–3 hrs	1–1½ hrs	½–¾ hr	25–35 min
315–550 CCA	3–3¾ hrs	1½–2 hrs	¾–1 hr	½–¾ hr
550–1000 CCA	3¾–7 hrs	2–3½ hrs	1–1¾ hrs	¾–1½ hrs

Marine and Deep-Cycle Batteries

Battery Rating	10A	20A
80 RC	3½ hrs	1¾ hrs
140 RC	5½ hrs	2¾ hrs
160 RC	6 hrs	3 hrs
180 RC	6½ hrs	3¼ hrs

These estimates assume a battery starting at approximately 50% charge.

Maintenance

Routine maintenance helps maximize charger life.

Cleaning

After each use:

• Clean battery clamps.
• Remove battery residue and acid.
• Wipe down the charger housing.
• Inspect cables for wear.

Periodic cleaning helps prevent corrosion and maintains reliable operation.

Storage

When storing the charger:

1. Unplug it from AC power.
2. Coil cables neatly.
3. Store upright.
4. Keep in a cool, dry indoor location.
5. Do not clip clamps together.
6. Avoid storing clamps against metal objects.

Proper storage helps prevent cable damage and corrosion.

Troubleshooting

Charger Will Not Turn On

Possible Causes:

• Dead AC outlet
• Loose electrical connection

Solutions:

• Check circuit breakers and fuses.
• Verify power cord connections.
• Inspect extension cords.

Battery Is Connected But Not Charging

Possible Cause:

• Poor clamp connection

Solution:

• Clean battery terminals.
• Reposition clamps.
• Ensure a solid connection to battery and frame.

Charger Makes Clicking Sounds

Possible Causes:

• Circuit breaker cycling
• Defective battery
• Shorted cables
• Reverse polarity

Solutions:

• Check charger settings.
• Inspect battery condition.
• Verify correct clamp connections.
• Replace damaged cables.

Charger Produces Loud Buzzing

Possible Causes:

• Transformer vibration
• Internal component issue

Solution:

• Mild buzzing may be normal.
• Persistent humming should be inspected by a qualified technician.

Engine Start Function Does Not Work Properly

Possible Causes:

• Excessive current draw
• Insufficient cooling time
• Poor battery connections
• Overheating protection activated

Solutions:

• Wait 3 minutes between cranking attempts.
• Check clamp connections.
• Verify AC power supply.
• Use Boost mode for 10–15 minutes before starting heavily discharged batteries.

Technical Specifications

Specification	Details
Product Type	Manual Timer-Controlled Battery Charger
Battery Compatibility	12V Lead-Acid (STD, AGM, GEL, Deep-Cycle)
Input Voltage	120V AC
Charging Modes	Charge, Boost, Engine Start
Timer Type	Manual
Display Type	Analog Ammeter
Cooling System	Internal Fan
Case Material	Metal

Specifications are based on information provided in the owner’s manual.

Warranty and Support

The Schumacher SC1667 includes a one-year limited warranty. Warranty details are available directly from Schumacher Electric.

Website:
www.schumacherelectric.com

Warranty Assistance:
1-800-621-5485

Repairs and Returns:
www.365rma.com

Official User Manual (PDF)