Automatic Battery Charger SC1303

Schumacher Automatic Battery Charger SC1303

The Schumacher SC1303 Automatic Battery Charger is designed to charge and maintain compatible 6V and 12V lead-acid batteries. It provides a 2A charging output for 6V batteries and a 10A charging output for 12V batteries, with automatic voltage detection and adjustable charging current based on battery size.

The charger supports standard (STD), Absorbed Glass Mat (AGM), and compatible deep-cycle lead-acid batteries. A Battery Type button allows selection between STD and AGM charging settings.

The SC1303 includes automatic charging, float mode monitoring, desulfation, and battery fault detection. After the connected battery reaches full charge, the charger automatically enters maintain mode to keep the battery charged by supplying a small amount of current when necessary.

The control panel includes charging status indicators, a battery-type selection button, and warning lights for reversed battery connections or defective batteries.

The charger operates from a grounded 120V AC electrical outlet and is intended for use with compatible automotive, powersports, and marine batteries.

Product Features

The Schumacher SC1303 includes the following features:

• Automatic 6V and 12V battery charging.
• 2A charging output for 6V batteries.
• 10A charging output for 12V batteries.
• Automatic voltage detection.
• Automatic charging current adjustment.
• STD and AGM battery-type selection.
• Support for compatible deep-cycle lead-acid batteries.
• Automatic charging mode.
• Float mode monitoring.
• Automatic battery maintenance.
• Desulfation mode.
• Automatic charge-abort protection.
• Reverse-polarity detection.
• Bad battery warning indicator.
• Yellow/orange charging status LED.
• Green charged/maintaining LED.
• Automatic startup protection.
• Battery clamps for connecting to a vehicle or battery terminals.

Technical Specifications

Battery Compatibility

The Schumacher SC1303 is designed for rechargeable lead-acid batteries.

The charger automatically detects whether a connected battery is 6V or 12V, while the battery type must be selected using the Battery Type button.

Supported Battery Types

Recommended Battery Capacities

Battery Types That Must Not Be Charged

The SC1303 must not be used to charge household dry-cell batteries.

These batteries may rupture during charging and cause personal injury or property damage.

Never charge a frozen battery.

Parts and Components

The SC1303 has a charger housing, carrying handle, control panel, AC power cord, and DC battery clamps.

Main Components

Control Panel and Button Functions

The SC1303 control panel includes LED status indicators and a Battery Type button.

Battery Type Button

The Battery Type button allows selection of the appropriate battery chemistry.

The available settings are STD and AGM.

STD Battery Setting

Standard lead-acid batteries are commonly used in cars, trucks, and motorcycles.

These batteries typically have vent caps and may be labeled as low-maintenance or maintenance-free.

They are designed to provide short bursts of electrical energy, such as those required to start an engine.

Standard starting batteries must not be used for deep-cycle applications unless specifically designed for that purpose.

AGM Battery Setting

AGM batteries use an absorbent glass mat that holds the battery electrolyte close to the plate material.

This type of battery is a form of sealed valve-regulated lead-acid (VRLA) battery.

AGM batteries are commonly used in:

• High-performance engine starting.
• Powersports applications.
• Deep-cycle applications.
• Solar power systems.
• Battery storage systems.

Select the AGM setting when charging an AGM battery.

LED Indicator Guide

The Schumacher SC1303 has three charging status indicators.

LED Status Table

Flashing Red LED – Reversed Battery Connections

A flashing red Clamps Reversed/Bad Battery LED indicates that the positive and negative connections are reversed.

Disconnect the charger from AC power before correcting the battery connections.

Solid Red LED – Bad Battery

A solid red Clamps Reversed/Bad Battery LED indicates that the charger has detected a problem with the battery.

The charger may stop charging if the battery cannot be charged normally.

Yellow/Orange LED – Charging

The yellow/orange Charging LED illuminates when the charger is actively charging the connected battery.

Pulsing Green LED – Charged/Maintaining

A pulsing green Charged/Maintaining LED indicates that charging is complete and the charger has switched to maintain mode.

In maintain mode, the charger supplies a small amount of current when necessary to keep the battery fully charged.

All Three LEDs Illuminate Briefly

When the charger is connected to an AC outlet, all three LEDs may illuminate for approximately two seconds and then turn off.

This is normal startup behavior.

Important Safety Instructions

WARNING: Risk of explosive gases, fire, electrical shock, and serious injury.

Lead-acid batteries produce explosive gases during normal operation. Follow all charger and battery manufacturer safety instructions before connecting or operating the SC1303.

General Safety Precautions

• Keep the charger away from children.
• Do not expose the charger to rain or snow.
• Use only attachments recommended or supplied by the manufacturer.
• Disconnect the charger by pulling the plug rather than the power cord.
• Do not operate the charger with a damaged power cord or plug.
• Do not use the charger if it has been dropped, struck, or otherwise damaged.
• Never disassemble the charger.
• Have repairs performed by qualified service personnel.
• Disconnect the charger from AC power before cleaning or maintenance.
• Avoid using extension cords unless necessary.
• Never attempt to charge a frozen battery.

Battery Explosion Prevention

• Never smoke near a battery or engine.
• Keep sparks and open flames away from batteries.
• Do not allow battery clamps to touch each other.
• Avoid dropping metal tools onto a battery.
• Keep charging equipment away from flammable materials.
• Follow all battery manufacturer warnings and instructions.

Personal Safety

Another person should be close enough to provide assistance when working near a lead-acid battery.

Wear complete eye protection and protective clothing.

Remove rings, bracelets, necklaces, watches, and other metal jewelry before working around battery terminals.

Keep fresh water and soap available when working near a battery.

Battery Acid Safety

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

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

Electrical Safety

The charger must be disconnected from the AC outlet before attaching or removing battery clamps.

Turning off the controls alone does not eliminate the risk of electrical shock during cleaning or maintenance.

Vehicle Starting Warning

Do not start a vehicle while the SC1303 is connected to an AC electrical outlet.

Starting the vehicle while charging may damage the battery charger.

Preparing the Battery for Charging

Before connecting the SC1303, inspect and prepare the battery.

Battery Preparation Instructions

1. Turn off all vehicle electrical accessories.
2. If the battery must be removed from the vehicle, disconnect the grounded battery terminal first.
3. Make sure the charging area is well ventilated.
4. Clean the battery terminals.
5. Prevent battery corrosion from contacting the eyes.
6. For serviceable batteries, add distilled water until the electrolyte reaches the level recommended by the battery manufacturer.
7. Do not overfill the battery cells.
8. Follow the manufacturer’s instructions for sealed or valve-regulated batteries.
9. Check the battery voltage using the vehicle owner’s manual or battery information.
10. Follow the battery manufacturer’s charging precautions and recommended charging rates.

Charger Placement Instructions

Proper charger placement helps prevent damage from battery gases, corrosion, and restricted ventilation.

Positioning the Charger

• Place the charger as far from the battery as the DC cables allow.
• Never place the charger directly above the battery.
• Do not allow battery acid to drip onto the charger.
• Do not operate the charger in an enclosed area without proper ventilation.
• Keep ventilation openings unobstructed.
• Never place a battery on top of the charger.

The charger should be placed on a dry, non-flammable surface during operation.

AC Power and Grounding Requirements

The Schumacher SC1303 operates from a nominal 120V AC electrical circuit.

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

Grounding Instructions

1. Use a grounded 120V AC outlet.
2. Confirm that the plug fits the outlet correctly.
3. Do not modify the supplied AC power cord or plug.
4. Never connect the charger to an ungrounded electrical system.
5. If the plug does not fit, have a suitable grounded outlet installed by a qualified electrician.

An improper electrical connection can cause electric shock or electrocution.

Adapter Plug Restrictions

The use of an adapter plug is not permitted in Canada under the regulations identified in the manual.

Using an adapter plug in the United States is not recommended.

Using an Extension Cord

Extension cords should only be used when necessary.

An extension cord must be properly wired, in good electrical condition, and compatible with the charger’s AC plug.

Extension Cord Requirements

The extension cord plug must have the same number, size, and shape of pins as the charger plug.

Setup and Assembly Instructions

The SC1303 requires minimal preparation before charging.

Preparing the Charger

1. Remove the cord wraps.
2. Uncoil the AC power cord.
3. Uncoil the DC charging cables.
4. Inspect the cables and clamps for damage.
5. Position the charger on a dry, non-flammable surface.
6. Keep the charger disconnected from AC power while connecting the battery clamps.
7. Follow the correct connection procedure for the battery location.

Connecting the Charger to a Battery Installed in a Vehicle

WARNING: A spark near a battery can cause an explosion.

Before connecting the charger, determine whether the vehicle uses a negative-ground or positive-ground electrical system.

Battery Terminal Identification

The positive terminal normally has a larger diameter than the negative terminal.

Connecting to a Negative-Ground Vehicle

Most vehicles use a negative-ground electrical system.

1. Turn off the vehicle ignition and electrical accessories.
2. Make sure the charger is disconnected from AC power.
3. Connect the red positive (+) clamp to the positive battery 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. Keep the clamps away from fuel lines, carburetors, and sheet-metal body panels.
6. Make sure both connections are secure.

Connecting to a Positive-Ground Vehicle

For a positive-ground vehicle:

1. Make sure the charger is disconnected from AC power.
2. Connect the black negative (-) clamp to the negative battery terminal.
3. Connect the red positive (+) clamp to a heavy-gauge metal part of the chassis or engine block away from the battery.
4. Make sure the connections are secure.

Disconnecting the Charger from a Vehicle

When charging is complete:

1. Disconnect the AC power cord.
2. Remove the clamp attached to the vehicle chassis or engine block.
3. Remove the clamp attached to the battery terminal.

Connecting the Charger to a Battery Outside the Vehicle

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

Required Battery Cable

Battery Connection Instructions

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

Disconnecting the Charger

Disconnect the charger from AC power first.

Remove the battery connections in the reverse order used for connecting, making the first disconnection as far from the battery as practical.

Marine Battery Charging

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

Charging a marine battery while it remains onboard requires equipment specifically designed for marine use.

How to Charge a Battery Installed in a Vehicle

The SC1303 can charge a compatible battery without removing it from the vehicle.

Charging Instructions

1. Turn off all vehicle accessories.
2. Keep the vehicle hood open.
3. Clean the battery terminals.
4. Place the charger on a dry, non-flammable surface.
5. Position the AC and DC cables away from fan blades, belts, pulleys, and other moving engine parts.
6. Connect the charger clamps according to the vehicle’s grounding system.
7. Plug the charger into a properly grounded 120V AC outlet.
8. Select the correct battery type using the Battery Type button.
9. Allow the charger to operate automatically.
10. Monitor the charging status LEDs.
11. When charging is complete, disconnect the charger from AC power.
12. Remove the clamp attached to the vehicle chassis.
13. Remove the remaining clamp from the battery terminal.

Charging Operation

After the charger is connected, it automatically detects the battery voltage and adjusts the charging current according to battery size.

The yellow/orange Charging LED illuminates during charging.

When the battery reaches full charge, the green Charged/Maintaining LED begins pulsing.

How to Charge a Battery Outside the Vehicle

A compatible 6V or 12V battery can also be charged outside a vehicle.

Charging Instructions

1. Place the battery in a well-ventilated area.
2. Clean the battery terminals.
3. Connect the battery clamps according to the battery-outside-vehicle connection procedure.
4. Plug the charger into a grounded 120V AC outlet.
5. Select the correct battery type.
6. Allow the charger to charge the battery automatically.
7. Monitor the charging status indicators.
8. When charging is complete, unplug the charger from AC power.
9. Disconnect the negative charger clamp.
10. Disconnect the positive charger clamp.

Marine batteries must be removed from the boat and charged on shore.

Automatic Voltage Detection

The SC1303 automatically detects the voltage of the connected battery.

Supported Charging Voltages

The charger does not require manual selection between 6V and 12V.

The Battery Type button is used to select STD or AGM battery chemistry, not the battery voltage.

Automatic Charge Rate Adjustment

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

This allows the charging process to operate at an appropriate current within the charger’s specified output ratings.

Charging Current Ratings

Battery Charging Time Chart

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

The manual includes the following comparison chart based on batteries discharged to approximately 50%.

Important: This is the general charging-rate comparison chart printed in the owner’s manual. The SC1303 does not offer selectable 6A, 12A, or 15A modes. Its specified outputs are 2A at 6V and 10A at 12V, with automatic current adjustment. The comparative times should not be treated as guaranteed SC1303 charging times, particularly for batteries outside its recommended capacity range.

Automatic Charging Mode

The SC1303 automatically charges a correctly connected battery.

How Automatic Charging Works

1. The charger detects the battery connection.
2. It identifies whether the connected battery is 6V or 12V.
3. The charger adjusts its charging current.
4. The yellow/orange Charging LED illuminates.
5. The charger continues charging until the battery reaches full charge.
6. The charger automatically switches to maintain mode.

The green Charged/Maintaining LED pulses when maintain mode is active.

Charge Completion Indicator

Charge completion is indicated by a pulsing green Charged/Maintaining LED.

When this indicator begins pulsing, the charger has switched from active charging to maintain mode.

Maintain Mode (Float Mode Monitoring)

The Schumacher SC1303 includes automatic battery maintenance.

Maintain mode keeps a healthy battery fully charged by supplying a small amount of charging current when necessary.

How Maintain Mode Works

After the battery reaches full charge:

• The green Charged/Maintaining LED begins pulsing.
• The charger monitors the battery.
• A small charging current is supplied when required.
• The battery is maintained at full charge.

Maintaining 6V and 12V Batteries

The SC1303 can maintain compatible 6V and 12V batteries.

The automatic maintenance function allows a healthy battery to remain connected for extended periods.

Maintain Mode Safety

The battery and charging process must still be checked occasionally.

Battery defects, vehicle electrical problems, improper connections, and excessive current draw may interfere with maintenance charging.

Maintain Mode Abort Protection

If the charger must provide its maximum maintenance current continuously for 12 hours, it enters abort mode.

This condition may occur because of an electrical load connected to the battery or a defective battery.

If the charger enters abort mode:

1. Check for electrical loads connected to the battery.
2. Remove any connected loads.
3. Have the battery checked if no electrical loads are present.
4. Replace the battery if necessary.

Desulfation Mode

The SC1303 includes an automatic desulfation process.

Desulfation Duration

Desulfation may take approximately 8–10 hours.

If desulfation fails, the charger stops charging and illuminates the red Clamps Reversed/Bad Battery LED.

The battery may require inspection or replacement.

Aborted Charge Protection

If charging cannot be completed normally, the charger automatically aborts the charging process.

What Happens When Charging Is Aborted?

• The charger stops supplying output current.
• The red Clamps Reversed/Bad Battery LED illuminates.
• The charging process does not continue normally.

What to Do After Charging Is Aborted

Do not continue attempting to charge a battery after the charger has aborted charging.

Have the battery checked and replace it if necessary.

Troubleshooting Guide

The following troubleshooting information covers charging failures, LED indicators, reverse-polarity conditions, and battery problems.

Schumacher SC1303 Troubleshooting Table

Charger Will Not Turn On

If the SC1303 does not operate when connected:

Check the AC Outlet

1. Confirm that the charger is connected to a grounded outlet.
2. Check whether the outlet has power.
3. Check for a blown fuse or tripped circuit breaker.

Check the Power Cord

Inspect the power cord and extension cord connections for loose-fitting plugs.

Do not operate the charger with a damaged electrical cord or plug.

Check the Battery

If the electrical connections are correct but the charger does not operate, the battery may be defective.

Have the battery checked.

Battery Clamps Do Not Spark

The SC1303 includes an auto-start feature.

The charger does not supply current to the clamps until a battery is properly connected.

The absence of sparks when the clamps touch is normal.

The clamps must still never be intentionally touched together.

All Three LEDs Illuminate Briefly

When the charger is connected to an AC outlet, all three LEDs may illuminate for approximately two seconds and then turn off.

This is normal behavior.

Cannot Select 6V or 12V Charging

The SC1303 uses automatic voltage detection.

It identifies the connected battery voltage automatically.

Manual selection between 6V and 12V charging is not required.

Red LED Remains Illuminated

A solid red Clamps Reversed/Bad Battery LED indicates that the charger has detected a battery problem.

Several conditions can cause this indicator to illuminate.

Battery Voltage Remains Too Low

The charger may detect a problem when battery voltage remains below the following thresholds after two hours of charging.

The battery may be defective.

Remove any external electrical loads and have the battery checked or replaced if necessary.

Excessive Current in Maintain Mode

The troubleshooting instructions identify a fault when output current exceeds 1.5A continuously for 12 hours during maintain mode.

Check for electrical loads draining the battery.

If no loads are connected, have the battery checked.

Unsuccessful Desulfation

If desulfation does not restore the battery sufficiently, the charger stops charging.

The red LED illuminates.

Have the battery checked or replaced.

Charging Progress Stops

The charger may detect inadequate charging progress when battery voltage remains below:

The battery may be overheated, too large, or affected by a short circuit.

Allow an overheated battery to cool.

Have the battery checked or replaced if necessary.

Battery Capacity Is Too Low or Battery Is Too Old

A fault may occur when the initial battery voltage is below:

This condition is identified when the total charging input is less than 1.5Ah.

The battery may have insufficient capacity or may be too old.

Have it inspected or replaced.

Battery Voltage Drops During Maintain Mode

The charger may identify a battery problem when voltage drops below:

The battery may not be holding its charge.

Check for connected electrical loads.

If no loads are present, have the battery inspected or replaced.

Maintenance and Cleaning Instructions

Regular cleaning helps prevent corrosion and damage to the battery charger.

Cleaning the Battery Clamps

After each charging session:

1. Disconnect the charger from AC power.
2. Disconnect the battery clamps.
3. Wipe away battery fluid or residue from the clamps.
4. Clean the clamps to prevent corrosion.

Cleaning the Charger Housing

Occasionally clean the outer housing using a soft cloth.

This helps preserve the finish and prevent corrosion.

Cable Maintenance

Coil the input and output cords neatly when the charger is not in use.

This helps prevent accidental cable damage.

Storage Instructions

The SC1303 must be stored indoors in a cool, dry location.

Proper Storage Procedure

1. Disconnect the charger from AC power.
2. Remove the battery clamps.
3. Clean the charger and clamps if necessary.
4. Coil the power and charging cables neatly.
5. Store the charger in an upright position.
6. Keep the charger in a cool, dry place.

Battery Clamp Storage Precautions

Do not store the clamps:

• Clipped together.
• Attached to the carrying handle.
• Attached to metal objects.
• Clipped around electrical cables.
• Attached to the charger’s input or output cords.

Two-Year Limited Warranty

The Schumacher SC1303 is covered by a two-year limited warranty.

Warranty Coverage

Warranty Repair or Replacement

If the charger develops a covered defect, Schumacher may repair the unit or replace it with a new or reconditioned charger.

The manufacturer determines whether repair or replacement is appropriate.

The purchaser must provide proof of purchase and pay shipping charges in advance when sending the charger for warranty service.

Warranty Exclusions

The warranty may be void if the charger:

• Is misused.
• Is handled carelessly.
• Is repaired or modified by an unauthorized person.
• Is resold through an unauthorized retailer.

Accessories not manufactured and approved by Schumacher Electric Corporation are not covered by the limited warranty.

Warranty Registration

The charger can be registered online at:

www.batterychargers.com

The warranty registration card should be submitted within 30 days of purchase.

Keep the original retail purchase receipt because it is required for warranty claims.

Customer Support and Repair Information

Schumacher Electric Corporation provides customer assistance for troubleshooting, warranty service, repairs, and returns.

Customer Support Details

Repair and Return Procedure

1. Contact Schumacher Customer Service at 1-800-621-5485.
2. Describe the charging problem.
3. Follow the troubleshooting assistance provided.
4. Request a Return Merchandise Authorization (RMA) number if repair or return is required.
5. Do not ship the charger until an RMA number has been issued.

The warranty registration mailing address must not be used to send the unit for repairs.

Frequently Asked Questions

1. What types of batteries can the Schumacher SC1303 charge?

The Schumacher SC1303 is designed to charge compatible 6V and 12V rechargeable lead-acid batteries, including standard (STD), AGM, and compatible deep-cycle types. The manufacturer recommends 12Ah batteries for 6V charging and 44–68Ah batteries for 12V charging.

2. How many amps does the Schumacher SC1303 battery charger provide?

The SC1303 provides a rated charging output of 2A at 6V and 10A at 12V. The charger automatically adjusts the charging current based on battery size.

3. Does the Schumacher SC1303 automatically detect 6V and 12V batteries?

Yes. The SC1303 uses Automatic Voltage Detection to identify whether a connected battery is 6V or 12V. Manual voltage selection is not required. The Battery Type button is used to select the STD or AGM setting.

4. What does a flashing red light mean on the Schumacher SC1303?

A flashing red Clamps Reversed/Bad Battery LED indicates that the battery connections are reversed. Disconnect the charger from AC power before correcting the positive and negative clamp connections.

5. What does a solid red light mean on the Schumacher SC1303?

A solid red LED indicates that the charger has detected a battery problem or that charging has been aborted. Possible causes include a defective battery, unsuccessful desulfation, inadequate charging progress, or a problem during maintain mode. The battery should be checked according to the troubleshooting instructions.

6. What does a pulsing green light mean on the Schumacher SC1303?

A pulsing green Charged/Maintaining LED means the battery is fully charged and the charger has automatically entered maintain mode. In this mode, the charger supplies a small charging current when necessary to keep the battery fully charged.

7. Can the Schumacher SC1303 remain connected to a battery for long-term maintenance?

Yes. The SC1303 includes automatic float mode monitoring designed to maintain a healthy 6V or 12V battery over extended periods. The battery and charging process must still be checked periodically because battery defects, electrical drains, or improper connections may affect maintenance operation.

8. Why does the Schumacher SC1303 stop charging before the battery is fully charged?

The SC1303 may abort charging if it detects a defective battery, unsuccessful desulfation, inadequate charging progress, or an abnormal condition during maintain mode. When charging is aborted, the red Clamps Reversed/Bad Battery LED illuminates and the charger stops supplying current. Do not continue attempting to charge the battery; have it checked or replaced if necessary.