Automatic Battery Charger SC1634

Schumacher Automatic Battery Charger SC1634

The Schumacher SC1634 Automatic Battery Charger & Engine Starter is designed to charge, maintain, test, and assist with starting vehicles equipped with compatible 12V lead-acid batteries. The unit combines automatic battery charging, a 50A boost function, battery voltage testing, alternator performance testing, and an engine-start feature.

The SC1634 uses internal ultracapacitors (UltraCaps) and a rechargeable lithium battery to store electrical energy for portable engine starting. This allows the engine-start function to operate even when the charger is disconnected from an AC electrical outlet.

The charger features a digital display, LED status indicators, selectable operating modes, battery clamps, wheels, and an extendable handle.

Three primary operating selections are available:

• 6A CHARGE: Charges compatible 12V lead-acid batteries.
• 50A BOOST: Quickly supplies additional charging current to a severely discharged or large-capacity battery before starting.
• ENGINE START: Provides additional current to assist engine cranking when the vehicle battery is weak.

The SC1634 also switches automatically to maintain mode after charging a healthy battery.

Product Features

The Schumacher SC1634 includes the following functions and features:

• Automatic 12V lead-acid battery charging.
• 6A charging mode.
• 50A boost mode.
• Engine-start assistance.
• Portable engine starting using internal ultracapacitors.
• Internal rechargeable lithium battery.
• Automatic battery maintenance mode.
• Desulfation function.
• Digital voltage and charging percentage display.
• Battery voltage tester.
• Alternator performance tester.
• Reverse-polarity warning indicator.
• Bad battery warning indicator.
• Battery charging status LEDs.
• UltraCap charging status LED.
• Internal lithium battery charging status LED.
• Automatic charging shutdown during specified fault conditions.
• Wheels and extendable handle for moving the charger.
• 120V AC power connection.
• Battery clamps for connection to the vehicle battery.

Technical Specifications

Compatible Battery Types

The SC1634 is intended for charging rechargeable 12V lead-acid batteries.

The English operating instructions identify these supported battery types:

The charger is designed for 12V charging. Its internal lithium battery is used to supply energy to the ultracapacitors for portable engine starting.

Warning: Do not use the SC1634 to charge household dry-cell batteries or batteries that are not compatible with the charger’s specified 12V lead-acid charging function.

The battery manufacturer’s charging instructions and recommended charging rates must also be followed.

Parts and Components

The SC1634 includes charging controls, status indicators, electrical connections, and components that support movement and storage.

Main Components

Assembly Instructions

The SC1634 must be assembled before its first use.

Assembly Parts and Tools

Attaching the Feet and Wheels

1. Remove the charger from its packaging.
2. Place the charger with its back facing downward on a flat surface.
3. Position the feet on the charger.
4. Secure the feet using the four supplied 1/4-20 × 3/4-inch screws.
5. Attach the wheels to the axle.
6. Remove the cord wraps and uncoil the cables before operation.

Extending the Handle

1. Locate the retractable handle.
2. Pull the handle upward.
3. Continue extending it until it locks into position.
4. If necessary, press the small silver buttons inward while adjusting the handle.

Control Panel and Button Functions

The SC1634 control panel includes a digital display, function buttons, and charging status LEDs.

Control Buttons

POWER ON/OFF Button

The POWER ON/OFF button enables or disables the front-panel display and operating controls.

When the AC cord is connected but the POWER ON/OFF button has not been pressed, the digital display and most LEDs remain off.

The CAP CHARGING and LITH CHARGING LEDs may continue indicating the charging condition of the internal components.

RATE Selection Button

The RATE button switches between the three operating selections.

The 6A CHARGE function is not recommended for industrial applications.

START/STOP Button

When the charger is connected to AC power, pressing START/STOP begins charging a properly connected battery.

When the charger is operating without an AC connection, START/STOP enables engine-crank detection for portable engine starting.

Digital Display Guide

The digital display provides information about battery voltage, charging percentage, internal ultracapacitor charge, and engine-start operation.

Display Information

The display can show:

• Vehicle battery voltage.
• Estimated vehicle battery charging percentage.
• Internal ultracapacitor charging percentage.
• Charging status.
• Engine-start readiness.
• Engine-start cooldown countdown.
• Error codes.

Voltage and Percentage Indicators

When the charger is connected to a battery but not actively charging, the display initially shows the internal ultracapacitor charge percentage.

After the ultracapacitors are fully charged, the display changes to the voltage measured at the battery clamps.

Display During Battery Charging

When charging starts, the display shows 12, indicating charging of a 12V battery.

In 6A CHARGE mode, the display alternates between the battery’s estimated charging percentage and 12, approximately every 10 seconds.

After charging is complete, the 12V CHARGING LED remains solid green and the display turns off to conserve energy during maintain mode.

LED Indicator Guide

Battery and Charging Status Indicators

Operating Mode LEDs

Important Safety Instructions

Warning: Risk of explosive gases, electric shock, fire, burns, and serious personal injury.

Lead-acid batteries produce explosive gases during normal operation. Safety precautions must be followed whenever charging, testing, or starting a vehicle battery.

General Safety Precautions

• Keep the charger away from children.
• Read the instructions before each use.
• Do not expose the charger to rain or snow.
• Do not use attachments that are not recommended or sold by the manufacturer.
• Disconnect the AC cord by pulling the plug, not the cord.
• Avoid using extension cords unless absolutely necessary.
• Do not operate the charger with a damaged power cord or plug.
• Do not use the charger after a severe impact, drop, or other damage.
• Never open or disassemble the charger.
• Have repairs performed by qualified service personnel using identical replacement parts.
• Turn off and unplug the charger before cleaning or maintenance.
• Never charge a frozen battery.
• Do not expose the internal power pack to fire or temperatures above 265°F (130°C).

Battery Explosion Prevention

• Never smoke near a battery or engine.
• Keep sparks and open flames away from the battery.
• Use the charger in a well-ventilated area.
• Do not allow the battery clamps to touch each other.
• Keep metal tools away from battery terminals.
• Remove metal jewelry, watches, bracelets, and rings before working near a battery.
• Follow the battery manufacturer’s safety instructions.
• Keep another person nearby when working around a lead-acid battery.

Personal Protection

Wear eye protection and protective clothing when working near lead-acid batteries.

Keep fresh water and soap nearby.

If battery acid contacts skin or clothing, wash the affected area immediately with soap and water.

If battery acid enters the eyes, flush the eyes with cold running water for at least 10 minutes and obtain immediate medical attention.

Charger Placement Safety

• Position the charger as far from the battery as the DC cables allow.
• Never place the charger directly above the battery.
• Do not place a battery on top of the charger.
• Do not allow battery acid to drip onto the charger.
• Do not operate the charger in a closed or poorly ventilated area.
• Keep ventilation openings clear.

Indoor and Outdoor Use Precautions

The operating instructions specify indoor use and warn against operating the charger outdoors.

The general safety section also describes precautions for temporary outdoor use, including protection from rain, snow, sleet, and other weather conditions, indoor storage, and no outdoor charging of the unit.

Because these sections differ, indoor operation is the stated operating instruction. Confirm any intended temporary outdoor use with Schumacher before proceeding.

AC Power and Grounding Requirements

The SC1634 is designed for a nominal 120V AC electrical circuit.

The charger must be connected to a properly grounded electrical outlet.

Grounding Instructions

1. Use a properly installed grounded 120V AC outlet.
2. Verify that the outlet matches the charger plug.
3. Do not modify the supplied AC plug.
4. Do not connect the charger to an ungrounded electrical system.

If the plug does not fit the outlet, a qualified electrician must install a suitable grounded outlet.

Extension Cord Requirements

Extension cords are not recommended.

If an extension cord is necessary, it must be properly wired, in good condition, and have a plug compatible with the charger.

Before Charging a Battery

Before connecting the SC1634 to a battery:

1. Confirm that the battery is a compatible 12V lead-acid battery.
2. Turn off all vehicle accessories.
3. Check the battery manufacturer’s charging precautions.
4. Clean the battery terminals.
5. Provide adequate ventilation around the battery.
6. Position the charger away from the battery.
7. Keep cables away from moving engine components.
8. Identify the battery’s positive and negative terminals.

For serviceable batteries with removable cell caps, add distilled water only as directed by the battery manufacturer. Do not overfill.

For sealed or valve-regulated batteries, follow the battery manufacturer’s charging instructions.

Connecting the Charger to a Battery Installed in a Vehicle

Warning: A spark near the battery can cause an explosion.

The charger must be switched off and disconnected from AC power before attaching or removing battery clamps.

Negative-Grounded Vehicle Connection

Most vehicles use a negative-ground electrical system.

1. Turn off the vehicle’s accessories.
2. Identify the positive and negative battery terminals.
3. Connect the red positive clamp to the battery’s positive (+) terminal.
4. Connect the black negative clamp to a heavy-gauge metal part of the vehicle chassis or engine block, away from the battery.
5. Do not connect the black clamp to fuel lines, a carburetor, or sheet-metal body panels.
6. Route the cables away from fan blades, belts, pulleys, and other moving parts.

Positive-Grounded Vehicle Connection

For a positive-grounded vehicle:

1. Connect the black negative clamp to the battery’s negative (-) terminal.
2. Connect the red positive clamp to a heavy-gauge metal part of the vehicle chassis or engine block, away from the battery.
3. Keep the connection away from fuel lines and moving engine components.

Disconnecting the Charger

1. Stop charging and turn the charger off.
2. Disconnect the AC power cord.
3. Remove the clamp connected to the vehicle chassis.
4. Remove the clamp connected to the battery terminal.

Connecting the Charger to a Battery Outside the Vehicle

When charging a battery that has been removed from a vehicle, an additional insulated battery cable is required for the negative connection.

Battery Connection Instructions

1. Place the battery in a well-ventilated area.
2. Identify the positive and negative terminals.
3. Attach a minimum 24-inch-long, 6 AWG insulated battery cable to the battery’s negative terminal.
4. Connect the charger’s red positive clamp to the battery’s positive terminal.
5. Position the free end of the insulated cable as far from the battery as practical.
6. Connect the charger’s black negative clamp to the free end of the cable.
7. Do not face the battery while making the final connection.

When disconnecting, switch off and unplug the charger, then remove the connections in reverse order, making the first disconnection as far from the battery as practical.

A marine battery must be removed from the boat and charged on shore.

How to Charge a Battery Installed in a Vehicle

The SC1634 can automatically charge a compatible 12V lead-acid battery while it remains installed in the vehicle.

Charging Instructions

1. Turn off all vehicle accessories.
2. Keep the vehicle hood open.
3. Clean the battery terminals.
4. Position the charger on a dry, non-flammable surface.
5. Route the AC and DC cables away from moving engine parts.
6. Connect the battery clamps using the correct grounded-vehicle procedure.
7. Plug the charger into a live, grounded 120V AC outlet.
8. Press POWER ON/OFF.
9. Select the required charging rate using the RATE button.
10. Press START/STOP to begin charging.
11. Allow the charger to complete the charging process.

When 6A CHARGE or 50A BOOST is selected, the charger may automatically use 50A BOOST during the first 10 minutes if needed.

After the first 10 minutes, the selected charging rate is used.

Stopping Battery Charging

1. Press START/STOP.
2. Press POWER ON/OFF.
3. Disconnect the charger from the AC outlet.
4. Remove the clamp connected to the vehicle chassis.
5. Remove the remaining clamp from the battery terminal.

How to Charge a Battery Outside the Vehicle

The battery must be placed in a well-ventilated location and connected using the separate-battery procedure.

Charging Instructions

1. Position the battery in a well-ventilated area.
2. Clean the battery terminals.
3. Connect the charger clamps according to the battery-outside-vehicle instructions.
4. Connect the charger to a grounded 120V AC outlet.
5. Press POWER ON/OFF.
6. Select the charging rate.
7. Press START/STOP to begin charging.
8. Allow the automatic charging cycle to complete.
9. Stop charging, turn the charger off, unplug the AC power cord, and disconnect the battery connections in the reverse order.

Charging Modes and Settings

The Schumacher SC1634 provides 6A charging, 50A boost, engine-start assistance, and automatic maintenance.

6A CHARGE Mode

The 6A CHARGE setting is designed for charging small and large compatible 12V batteries.

The charger automatically adjusts the charging current according to battery size during the charging process.

The charging percentage is displayed in this mode, alternating with the 12 display approximately every 10 seconds.

50A BOOST Mode

The 50A BOOST setting is intended to quickly add energy to a large-capacity or severely discharged battery before engine starting.

To use this setting:

1. Connect the charger to the battery.
2. Plug the charger into a grounded 120V AC outlet.
3. Press POWER ON/OFF.
4. Select 50A BOOST using the RATE button.
5. Press START/STOP to begin charging.

When first powered on with an AC connection, the SC1634 defaults to the 50A BOOST selection.

ENGINE START Mode

ENGINE START supplies additional current to assist with cranking a vehicle engine when the battery is weak.

The function can operate with or without an AC power connection.

Warning: ENGINE START must always be used with a battery installed in the vehicle. Using this function without a vehicle battery can damage the vehicle’s electrical system.

Battery Charging Time Chart

Charging time depends on the battery’s capacity, condition, age, and level of discharge.

The following charging-time estimates are provided in the manual.

These estimates are based on batteries discharged to approximately 50% capacity.

The 2A, 8A, and 10A columns are reference estimates from the manual, not additional selectable charge-rate modes on the SC1634. Its normal charging selection is 6A CHARGE.

Automatic Charging Mode

The SC1634 automatically manages the charging process for a compatible 12V battery.

After the battery reaches full charge, the charger automatically switches to maintain mode.

Charge Completion Indicator

A solid green 12V CHARGING LED indicates that the battery is fully charged and the charger has entered maintain mode.

The digital display and most other LEDs turn off to conserve energy.

Maintain Mode (Float Mode Monitoring)

Maintain mode keeps a healthy battery charged by supplying a small amount of current when needed.

When maintain mode is active:

• The 12V CHARGING LED remains solid green.
• The battery receives maintenance current as needed.
• The charger monitors the charging condition.

If the charger must supply its maximum maintenance current continuously for 12 hours, charging is aborted.

This can occur because of an electrical drain or a defective battery.

Maintain mode permits extended battery maintenance, but the battery and charging process must still be checked periodically.

Desulfation Mode

The SC1634 can detect a sulfated battery and enter desulfation mode.

Desulfation may take approximately 8 to 10 hours.

When sulfation is detected, the digital display shows SUL.

If desulfation is unsuccessful after 10 hours, the charger stops charging and enters abort mode.

The red BAD BATTERY LED illuminates.

The battery should then be inspected or replaced.

Aborted Charge Protection

If the charger cannot complete a normal charging cycle, it stops the charging process.

When charging is aborted:

1. The charging output switches off.
2. The red BAD BATTERY LED illuminates.
3. An error code appears on the display.

Do not repeatedly attempt to charge a battery after an aborted charge. Have the battery checked or replaced.

Using Engine Start With an AC Power Connection

The engine-start function can assist a vehicle with a weak or discharged battery while the charger is plugged into a grounded electrical outlet.

Engine Starting Instructions

1. Make sure the charger is unplugged from AC power.
2. Connect the battery clamps according to the instructions for a battery installed in the vehicle.
3. Plug the charger into a live, grounded 120V AC outlet.
4. Press POWER ON/OFF.
5. Press the RATE button until the green ENGINE START LED is illuminated.
6. Press START/STOP.
7. Crank the engine until it starts or until 5 seconds have passed.
8. Do not crank during the required cooldown period.
9. If the engine does not start, charge the battery for another 5 minutes before attempting to start it again.
10. Once the engine starts, unplug the AC power cord before disconnecting the battery clamps.

Engine Starting in Extremely Cold Weather

During extremely cold weather, or when battery voltage is below 2V, charge the battery for 5 minutes before attempting engine starting.

Important Engine Start Warning

If the battery has been charged but the vehicle still does not start, do not continue using ENGINE START.

The battery or vehicle should be checked.

If the engine cranks normally but fails to start, stop cranking until the underlying vehicle problem has been diagnosed.

AC Engine Start Display States

During engine starting with AC power, the charger progresses through several operating states.

Wait for Ready

The charger initially charges the battery for approximately 2 minutes before entering the waiting-for-cranking state.

The display shows On.

Cranking during this preparation period is not recommended for severely discharged batteries.

Wait for Cranking

The display shows rdy.

The charger waits for the engine to be cranked before delivering the engine-start current.

Cranking

When engine cranking is detected, the charger automatically supplies the required output up to its maximum capability.

The cranking output is provided for up to 5 seconds.

Cooldown

The charger has a mandatory 3-minute cooldown cycle.

The display counts down from 180 seconds to 0.

After cooldown, rdy appears again.

After 2 hours in engine-start operation, the unit automatically returns to Tester mode.

Using Portable Engine Start Without AC Power

The SC1634 can assist with starting an engine even when disconnected from an AC outlet.

This function uses internal ultracapacitors and a rechargeable lithium battery.

How the Portable Engine Starter Works

The ultracapacitors store electrical energy for engine starting.

When AC power is connected, the ultracapacitors are charged using AC power.

When the charger is disconnected from AC power, the internal lithium battery charges the ultracapacitors.

Charging the ultracapacitors through AC power is faster than charging them using the internal lithium battery.

Preparing for Portable Engine Starting

For best results, charge the internal energy components before portable use.

1. Disconnect the battery clamps from the vehicle.
2. Connect the charger to a grounded 120V AC outlet.
3. Allow the internal ultracapacitors and lithium battery to charge.
4. Wait until both CAP CHARGING and LITH CHARGING LEDs are solid green.
5. Disconnect the AC power cord before using the charger in portable mode.

If the unit has been connected to AC power for more than one day, neither LED is flashing, and full charging is not indicated, disconnect and reconnect the AC power to reset charging.

Portable Engine Start Instructions

1. Press POWER ON/OFF.
2. The green ENGINE START LED illuminates.
3. If the ultracapacitors need charging, the internal lithium battery begins charging them.
4. The display shows the ultracapacitor charging percentage.
5. When ultracapacitor charge reaches 100%, the display switches to voltage at the battery clamps.
6. Connect the charger to the vehicle battery using the correct battery-clamp procedure.
7. Wait until the ultracapacitors are fully charged.
8. Press START/STOP.
9. The display shows rdy, indicating that the unit is ready to detect engine cranking.
10. Crank the vehicle engine.
11. When cranking is detected, the display changes to On and the ultracapacitors provide starting power.
12. Continue cranking until the engine starts or the display returns to the ultracapacitor charging percentage.
13. If the engine does not start, repeat the starting sequence after the ultracapacitors recharge.

Immediate Portable Engine Start

Pressing and holding START/STOP activates immediate ultracapacitor output.

The display changes to On, and the unit supplies maximum ultracapacitor power without waiting to detect engine cranking.

Portable Engine Start Limitations

When the charger is disconnected from AC power, ENGINE START is the only available operating selection.

The 6A CHARGE and 50A BOOST charging functions cannot be used without an AC connection.

When the Display Shows Chg

If the display shows Chg, the internal lithium battery does not have sufficient energy to recharge the ultracapacitors for another portable starting attempt.

The CAP CHARGING and LITH CHARGING LEDs are off.

Connect the SC1634 to AC power to recharge its internal components before portable use continues.

Stopping Portable Engine Start

1. Press START/STOP.
2. Press POWER ON/OFF.
3. Disconnect the battery clamps from the vehicle using the proper disconnection sequence.
4. Connect the charger to a grounded 120V AC outlet.
5. Recharge the internal ultracapacitors and lithium battery.

How to Recharge the Internal Ultracapacitors and Lithium Battery

The charger includes internal energy storage components used for portable engine starting.

Internal Charging Instructions

1. Disconnect the charger clamps from the vehicle battery.
2. Connect the unit to a live, grounded 120V AC outlet.
3. Monitor the CAP CHARGING LED.
4. Monitor the LITH CHARGING LED.
5. Allow both indicators to become solid green.

The internal components should be recharged periodically to maintain portable engine-start readiness.

Tester and Charger Modes

The SC1634 can work as a battery tester or charger.

When initially connected to AC power and powered on, the charger operates in Tester mode after the internal ultracapacitors are fully charged.

Switching Between Modes

Using the Battery Voltage Tester

The SC1634 includes a battery voltage testing function.

Battery Voltage Test Instructions

1. Disconnect the charger from the AC outlet.
2. Connect the battery clamps according to the correct connection procedure.
3. Connect the charger to a grounded 120V AC outlet.
4. Allow the internal ultracapacitors to become fully charged.
5. Wait until the display changes from the ultracapacitor charging percentage to battery voltage.
6. Check that the V VOLTAGE indicator is illuminated.
7. Read the voltage shown on the digital display.

Battery Voltage Reference Table

The manual also provides 24V reference readings in its voltage-testing chart. This does not change the charger’s specified 12V-only battery charging application.

The battery voltage reading may be affected by surface charge and should not be treated as a complete battery-condition diagnosis.

The testing function is intended for batteries, not for devices whose voltage changes rapidly.

Using the Alternator Performance Tester

The SC1634 can measure battery voltage while the vehicle engine is running to help evaluate alternator performance.

Alternator Test Instructions

1. Disconnect the charger from AC power.
2. Connect the clamps to the vehicle battery using the correct procedure.
3. Connect the charger to a grounded 120V AC outlet.
4. Press POWER ON/OFF.
5. Wait until the ultracapacitors are fully charged.
6. Confirm that battery voltage appears on the digital display.
7. Start the vehicle engine.
8. Run the engine at approximately 2,000 RPM for 30 seconds.
9. Turn on the headlights or other vehicle accessories.
10. Read the voltage displayed by the charger.

Alternator Voltage Results

The vehicle owner’s manual should be consulted for the appropriate alternator voltage range for the specific vehicle.

Digital Display Messages

The following messages appear during operation and testing.

Error Codes and Troubleshooting

The SC1634 displays error codes when it detects a battery problem, incorrect connection, charging failure, or internal protection condition.

SC1634 Error Code Table

F01 – Battery Voltage Too Low

F01 appears when battery voltage remains below 10V after two hours of charging.

The battery may be defective.

Have the battery inspected or replaced.

SUL – Battery Sulfation Detected

The SUL message indicates that the charger has detected a sulfated battery.

The charger enters desulfation mode.

If the process is unsuccessful after 10 hours, charging aborts.

F02 – Desulfation Failed

F02 means the charger was unable to desulfate the battery.

The battery should be checked or replaced.

F03 – Full-Charge Voltage Not Reached

F03 appears when the battery does not reach the required full-charge voltage.

This may occur when charging a large battery or battery bank using too low a current setting.

Try an appropriate higher charging setting, or have the battery checked or replaced.

F04 – Battery Clamps Reversed

F04 indicates reversed battery connections.

The red CLAMPS REVERSED LED flashes.

Correction:

1. Turn off the charger.
2. Disconnect it from AC power.
3. Correct the battery-clamp connections.
4. Reconnect the charger using the proper procedure.

F05 – Battery Cannot Maintain Charge

F05 occurs when the charger cannot keep the battery fully charged in maintain mode.

An external electrical load or a defective battery may be responsible.

Remove connected loads. If the problem continues without an external load, have the battery checked or replaced.

F06 – Battery Overheating

F06 indicates that the battery may be experiencing excessive heating or thermal runaway.

The charger automatically stops supplying current.

Have the battery checked or replaced.

F07 – Charger Overheating

F07 indicates that the charger’s internal temperature has exceeded its operating limit.

Check the side ventilation openings and remove any obstruction.

Move the charger out of direct sunlight and into a shaded location.

F08 – Low Battery Voltage During Maintain Mode

F08 appears when battery voltage drops too low during maintain mode.

Remove external electrical loads.

If the battery still cannot maintain its charge, have it checked or replaced.

F12 – Internal Lithium Battery Fault

F12 indicates that the internal lithium battery cannot be charged adequately.

The internal lithium battery is defective and requires qualified replacement service.

General Troubleshooting Guide

Charger Does Not Turn On

Engine Start Cycle Is Short or Does Not Begin

Battery Percentage Does Not Appear

When initially connected, the display may show battery voltage rather than a charging percentage.

The charging percentage is displayed during the appropriate charging operation.

12V CHARGING LED Does Not Light Immediately

When a battery is correctly connected, charging may begin after approximately 30 seconds if START/STOP is not pressed.

This delay is normal.

12V CHARGING LED Never Lights

Low battery voltage may prevent charging from beginning automatically.

Press START/STOP to begin charging.

BAD BATTERY LED Remains Solid Red

A solid red BAD BATTERY LED may indicate:

• Battery voltage remained below 10V after two hours of charging.
• Maintain-mode output exceeded 1.5A for 12 hours.
• Desulfation failed.
• Charging progress stopped while battery voltage remained below 14.2V.
• Battery voltage dropped below 10.8V during maintain mode.

Remove any connected electrical loads.

If the battery is overheating, allow it to cool.

Have the battery checked or replaced when the fault persists.

Resetting the Charger

To reset after a fault where resetting is appropriate:

1. Disconnect the charger from the AC outlet.
2. Wait a few moments.
3. Reconnect the charger.

Do not continue charging a battery that repeatedly enters aborted-charge mode.

Maintenance and Care

Regular care helps keep the SC1634 operating properly.

Maintaining the Internal Ultracapacitors and Lithium Battery

Periodically connect the charger to a grounded 120V AC outlet.

Keep it connected until:

• CAP CHARGING LED is solid green.
• LITH CHARGING LED is solid green.

This keeps the internal energy storage components ready for portable engine-start operation.

Cleaning the Battery Clamps

After charging:

1. Turn off the charger.
2. Disconnect it from AC power.
3. Remove the battery clamps.
4. Wipe away any battery fluid or residue from the clamps.

Cleaning the clamps helps prevent corrosion.

Cleaning the Charger Housing

Occasionally clean the outer housing using a soft cloth.

The charger must be off and disconnected from AC power before cleaning.

Preventing Cable Damage

Coil the AC power cord and DC output cables neatly after use.

Avoid storage arrangements that could damage the cords or clamps.

Storage Instructions

Store the SC1634:

• Indoors.
• In a cool, dry location.
• Unplugged from AC power.
• Powered off.
• In an upright position.
• With input and output cables neatly coiled.

Do not store battery clamps touching each other, attached to metal objects, or clipped onto the cables.

Storage Temperature

Replacement Parts and Repair Service

Replacement parts and repair information are available through Schumacher Electric.

Service Information

Have servicing performed by qualified repair personnel using identical replacement parts.

The charger must not be disassembled by the user.

Limited Warranty

The SC1634 owner’s manual includes limited warranty information.

Warranty Duration

The English section states a one-year limited warranty, while the Spanish and French sections state a two-year limited warranty.

Because the warranty periods differ within this document, the applicable period should be confirmed with Schumacher for the purchased unit.

Warranty Information and Registration

For limited warranty information:

• Visit schumacherelectric.com.
• Call 1-800-621-5485 to request a warranty copy.
• Register the product online at schumacherelectric.com.

Repairs and Returns

Repair and return requests are handled through:

365rma.com

Customer Support Information

Frequently Asked Questions

1. What types of batteries can the Schumacher SC1634 charge?

The Schumacher SC1634 is designed to charge 12V rechargeable lead-acid batteries, including STD, AGM, GEL, and deep-cycle batteries. It should not be used to charge household dry-cell batteries or incompatible battery chemistries.

2. What is the difference between 6A CHARGE and 50A BOOST on the Schumacher SC1634?

The 6A CHARGE setting is used for normal charging of compatible 12V batteries. The 50A BOOST setting quickly adds energy to a severely discharged or large-capacity battery before starting the engine. The charger may automatically use 50A BOOST during the first 10 minutes of charging when needed.

3. Can the Schumacher SC1634 start an engine without being plugged into an electrical outlet?

Yes. The SC1634 uses internal ultracapacitors and a rechargeable lithium battery for portable engine-start assistance. The internal lithium battery supplies energy to the ultracapacitors when AC power is disconnected. Only ENGINE START is available in this portable operating mode.

4. How do I know when the Schumacher SC1634 has fully charged a battery?

When the vehicle battery is fully charged, the 12V CHARGING LED remains solid green, indicating that the charger has entered maintain mode. The digital display and most other LEDs turn off to conserve energy.

5. What does F04 mean on the Schumacher SC1634 battery charger?

Error code F04 means the positive and negative battery connections are reversed. The CLAMPS REVERSED LED also flashes red. Turn off and unplug the charger before correcting the battery-clamp connections.

6. Why does the Schumacher SC1634 show Chg when using portable engine start?

The Chg message means the internal lithium battery cannot supply enough energy to recharge the ultracapacitors for portable engine starting. Connect the unit to a grounded 120V AC outlet and recharge the internal components before using portable engine start again.

7. How long does the Schumacher SC1634 engine-start cooldown take?

During AC-powered engine starting, the charger uses a mandatory 3-minute (180-second) cooldown period. The display counts down from 180 to 0. After the countdown, rdy appears, indicating readiness for another starting attempt.

8. Can the Schumacher SC1634 test a vehicle’s alternator?

Yes. The SC1634 includes an alternator performance tester. With the engine running at approximately 2,000 RPM for 30 seconds and the headlights or other accessories switched on, the charger measures voltage at the battery clamps. The manual identifies 13.4V to 14.6V as its normal reference range, while the vehicle manufacturer’s voltage specifications should also be followed.