All information contained in the Education and FAQ sections of this website pertaining to battery chargers and the charging process is for general, informational use only. Please refer to your Schumacher battery charger for specific product information, instructions and features.

About Charging Types

  • What is Microprocessor Controlled Charging?

    A microprocessor controlled battery charger is designed to provide fast, safe and efficient charging to a wide variety of battery types and sizes. Advanced microprocessor controlled algorithms monitor the charging process to avoid battery damage caused by overcharging. Simply put, the charger collects information from the battery and adjusts the charge current and voltage based on this information. This allows the battery to be charged quickly, correctly, and completely when using a microprocessor controlled battery charger. Because of this, fast charging does not have negative effects on the capacity of the battery and on battery cycle-life. The multi-phase charging process ensures that each battery gets the power it needs in a manner that is best for the health of the battery ensuring that all of the energy is properly absorbed by the battery whether it’s a Conventional, AGM, Gel Cell, Marine or Deep Cycle battery. Microprocessor controlled battery chargers can remain connected to the battery indefinitely and will not overcharge or damage it. Microprocessor controlled battery chargers are faster, safer and certainly more efficient than "old school" transformer type battery chargers.

  • What is Automatic Charging?

    When an automatic charge is performed, the charger stops charging and switches to the Maintain Mode (Float-Mode Monitoring) automatically after the battery is fully charged. Automatic chargers are more forgiving on the battery than manual chargers but are not designed for indefinite or maintenance use. Automatic chargers use a cycling process (see Maintain Mode) to prevent overcharging the battery.

  • What is Manual Charging?

    When a manual charge is performed, the charger will continue to charge and will not cycle or shut down by itself, even after the battery is fully charged. It will continue to put current at the selected setting to the battery until the charger is disconnected. You must keep a visual check on the ammeter to determine when the battery is fully charged. The use of a hydrometer or voltmeter to monitor the battery state of charge is recommended for use with all manual battery chargers. Be sure to monitor the charging process and stop it when the battery is charged. Not doing so may cause damage to the battery or result in other property damage or personal injury.

  • What is Maintain Mode?

    When the CHARGED LED is lit; the charger has started Maintain Mode. In this mode, the charger keeps the battery fully charged by delivering a small current when necessary. If the battery voltage drops below a preset level, the charger will go back in to Charge Mode until the battery voltage returns to the full charge level, which at this point the charger will return to Maintain Mode. The charger automatically switches between Charge Mode and Maintain Mode as necessary. The CHARGED LED will cycle on when the battery is at full charge and off when the voltage drops below a preset level and the charger goes into Charge Mode. The cycle will continue, and the CHARGED LED will stay on for longer periods of time as the battery becomes more fully charged. The voltage is maintained at a level determined by the BATTERY TYPE selected.


    NOTE: The maintain mode technology utilized in Schumacher’s maintainers allows you to safely charge and maintain a healthy battery for extended periods of time. However, problems with the battery, electrical problems in the vehicle, improper connections or other unanticipated conditions could cause excessive voltage draws. As such, occasionally monitoring the battery and the charging process is recommended.

About Battery Settings

  • When should I use a 2-amp, 10-amp, 12-amp, or 15-amp charge rate?

    This depends on how fast you want to charge your battery and the size of the actual battery you are charging. The higher the amp setting, the faster your battery will charge. For smaller batteries like lawn/tractors and motorcycles, we suggest a 2-amp charge rate, as higher charge rates may create a dangerous condition. Check your battery specifications for the charge rate.

  • Why doesn't my automatic battery charger shut off in the 2-amp position when charging my vehicle or deep-cycle battery?

    The 2-amp charge rate is intended for small batteries such as motorcycles, snowmobiles and lawn garden tractors. Consequently, when trying to charge a larger battery at that rate, it will take a very long time and the battery may discharge at a greater rate than the 2-amp charge can provide. It is better to charge a deep cycle battery at a higher charge rate like 6-amps, 10-amps or higher. However, check you battery specifications for the proper charge rate.

About Meters

  • How do I read the amp meter?

    The amp meter shows how much current the battery charger is outputting to the battery. When you turn on the charger, it outputs a high amount of current (electrical power). For example, if you select the 12-amp rate to charge the battery, the charger needle will be closer to the 12 on the right side. As the battery charges, the needle will drop to approximately half of the selected amperage rate indicating the battery is fully charged (For example: 6-amps).

  • Why is there more than one red area on the charger's amp meter?

    The red area represents the charge rate you selected at the beginning of battery charging. The red area on the far right is for the higher, amperage charge rate. The red area to the left indicates rates for the 2-amp position. In both instances, the needle starts in the red area, and as the battery becomes charged, drops to the left towards the larger green area.

  • What does it mean when the green LED blinks ON/OFF and the needle bounces?

    All automatic battery chargers in the automotive market today have some sort of voltage regulation to prevent overcharging the battery. The rate of the flashing is dependent on the battery type, its rated capacity, the degree of discharge, its age, the temperature, as well as the amperage rating of the battery charger.

    If the charger's green LED begins blinking when you connect the charger clips to the battery, the amperage in-rush current to the battery is reaching the pre-set shut-off voltage and the charger is shutting down. The voltage will drop as soon as the charger shuts down, turning the charger back on. This may also mean the charger has detected a battery problem - for instance, its ability to take or hold a charge. Sometimes a battery may be sulfated (accumulation of lead sulfate on the battery plates), and the sulfation is creating a high resistance to the current flow (ability to accept a charge). Or, perhaps the battery is deeply discharged (below 8-volts).

  • There is no meter reading, but I hear a hum. How can I tell if my battery charger is working?

    Hearing a slight humming noise is normal, and a sign that the transformer is powered up and working. Use a volt/amp meter or battery tester to check if the battery is charged.

About Battery Chargers

  • Digital Battery Charger Error Code Explanation Chart

    Error Code Description Reason/Solution
    F01 The battery voltage is still under 10V (for a 12V battery) or 5V (for a 6V battery) after 2 hours of charging.

    Could be caused by trying to charge a 6V battery on a 12V setting or charger, or the battery could be bad, have it checked or replaced.

    F02 The charger cannot desulfate the battery.

    The battery could not be desulfated, have it checked or replaced.

    F03 The battery was unable to reach the "full charged" voltage.

    Could be caused by trying to charge a large battery or bank of batteries on too low of a current setting or the battery may have a shorted cell. Try again with a higher current setting or have the battery checked or replaced.

    F04 The connections to the battery are reversed.

    The battery is connected backwards. Unplug the charger and reverse the connections to the battery.

    F05 The charger was unable to keep the battery fully charged in maintain mode.

    The battery won't hold a charge. Could be caused by a drain on the battery or the battery could be bad. Make sure there are no loads on the battery. If there are remove them. 
    If there are none, have the battery checked or replaced.

    F06 The charger detected that the battery may be getting too hot (thermal runaway).

    The charger automatically shuts the current off if it detects the battery may be getting too hot or the battery may have a shorted cell. Have the battery checked or replaced.


  • Why doesn't my automatic charger charge my battery?

    An automatic charger is designed to power the transformer when you first plug it into a receptacle. The automatic charger needs to “see” at least 4 volts in the battery to power up the circuitry. This initializes the charge sequence. When a completely discharged battery, or one with less than 4 volts charge remaining, is attached to the charger, the charger never “sees” this battery and will not begin the charging cycle. It will also cancel out the Engine Start function. The yellow charging light will also not come on. The meter (where used) will remain in the default “100%” position.

    NOTE: Batteries that remain lower than 4 volts state of charge are often defective or just worn out. It is always best (safer) to check the battery with a hydrometer or Schumacher tester before charging.

  • The charger's green light is on, but I still cannot start my car - why?

    In cold weather, a battery's chemistry changes and gives the battery charger a false voltage signal. When this happens, remove the battery from the vehicle and move it to a warm location to warm up before charging. Never charge a frozen battery.

    If the charger has a deep-cycle setting, try charging the battery for a short period of time at a higher, amperage charge rate. Then, try starting the vehicle again.

  • Why doesn't the green light stay on when my battery is completely charged?

    Three reasons:

    1. The electronic control circuit board and LED lights use a minor amount of battery power to operate and to determine the battery's state-of-charge. This results in the battery charger having to periodically charge the battery back to full charge. Consequently, the green light goes on and off as this process occurs.
    2. All batteries have some internal power losses, which the charger is replenishing similar to #1.
    3. The length of time that the green light is on is dependent on the battery type, its rated capacity, the degree of discharge, its age, and temperature.
  • Why don't I get sparks when I touch the battery clips together, creating a short?

    With electronic short-circuit protection, the battery charger must be able to measure a battery's voltage before it turns on. There is no output power in the clips until they are hooked up to a lead-acid battery.

  • How long can I use the Engine Start/Cranking Assist on my charger?

    The engine start/cranking assist feature on your charger is for short duration only (typically 3 to 5 seconds ON and 5 minutes OFF). See the front panel of your charger for the recommended crank time your charger allows. Charge the battery for 15 minutes before using engine start/cranking assist. After 15 minutes of charging, set the selector switch to the Engine Start/Cranking Assist position. Then try to start the engine using the ignition switch.

    If the engine fails to start within 3 to 5 seconds, stop cranking. Set the selector switch to a regular charge mode for another 10 to 15 minutes before trying to start the engine again. (You should not attempt to charge your battery on the engine start setting. Doing so could cause damage to your battery or cause other property damage or personal injury.) This rating is a UL standard based on the amperage output of the charger at 7.2 volts for 5 seconds. Recommended cranking assist cycles less than 5 seconds are in place to allow the charger to dissipate the heat generated by the increased power output through the transformer. Exceeding the recommended time duration of your charger's cranking assist cycle can cause damage to the charger's internal circuitry.

  • How long can I leave my charger connected to my battery?

    The type of charger you are using more accurately determines this, but generally your battery charger is safe to leave powered up and connected to your battery until the battery has reached a full charge. Manual chargers should be removed as soon as the battery has reached a full charge. These chargers will not cycle or shut down by themselves. They will continue to put a current through the battery until they are disconnected. The use of a hydrometer or voltmeter to monitor state of charge is recommended for use with manual battery chargers.

    Automatic chargers are more forgiving on your battery than manual chargers, but they are not designed for indefinite use. They utilize a cycling process, as described above, to prevent overcharging of the battery. The only charger recommended for extended or storage application is the 1.5 amp 12-volt charger specifically designed for long term, slow trickle charging/maintenance applications. However, problems with the battery, electrical problems in the vehicle, improper connections or other unanticipated conditions could cause excessive voltage draws. As such, occasionally monitoring the battery and the charging process is recommended.

  • Why can't I measure a voltage when connecting my volt meter to the battery clips?

    No output power is supplied until the battery charger's clips are hooked up to the battery. Then, it will measure and show the battery's voltage.

  • How do I tell what type of battery I have; Flooded, AGM or Gel?

    Flooded or Wet Cell batteries are the most common lead-acid battery type in use today. They usually are not sealed and electrolyte can be added through holes in the top casing of the battery. Gel Cell batteries are sealed and cannot be re-filled with electrolyte. Therefore they have a smooth top with no access holes. AGM (Absorbed Glass Mat) batteries are the latest step in the evolution of lead-acid batteries. They are sealed like Gel Cell batteries but are smaller and can be recognized by their compact size.

  • What is the correct charging voltage for my battery?

    That depends on the battery. While most of today’s automotive and marine batteries are 12 volt, some motorcycle and lawn tractor batteries are 6 volt. Check the battery and the owner’s manual of the vehicle the battery came out of for the correct voltage. The value of the charge rate voltage is determined by the battery manufacturer. Deviating from the recommended values will under or overcharge the battery – both of which will reduce the battery’s life and performance.

  • What is a trickle charger?

    The difference between a float charger and a trickle charger is that the float charger has circuitry to prevent overcharging the battery. It senses when the battery voltage is at the maximum level and temporarily shuts off the charge (floats voltage at zero or a very minimal charge until it senses that the battery output voltage has fallen and then resumes charging). It may be kept connected indefinitely. A trickle charger, on the other hand, will charge no matter whether the battery is fully charged or not, so it needs to be connected and disconnected periodically. If left in place too long, it will eventually boil the electrolyte out of the cells or damage the plates. Trickle chargers will work to keep the battery charged, if used once a month or so for a day or two, but the float chargers can be left connected longer without potential harm to the battery.

  • What happens if the power goes out and comes back on during charging?

    That depends on what charger you are using. A manual charger will keep charging as if it was just turned on. An automatic charger on the other hand may or may not continue charging depending on where it was at in the charging process when the power went out. If the battery is still sufficiently discharged, the charger will continue to charge the battery, but if the battery was almost fully charged, the charger may go into maintain mode early. The only effect this will have on your battery is it may take a longer time to reach a full charge. You may also have to readjust the settings because the charger will come back on with the default settings.

  • How can I tell if my battery needs to be replaced?

    If your battery won’t accept a charge or won’t stay charged as long as it used to, replace it.

  • Can a Schumacher charger be used to charge more than one battery at a time?

    Most cars and boats have 12 volt batteries, two batteries are used to gain more amperage, meaning they are wired in parallel but the voltage stays the same. Batteries wired in series (like a flashlight) give double the voltage (two 12 volt batteries wired in series makes 24 volts but your amperage stays constant.) To charge both batteries at the same time you need to make sure they are wired in parallel. The two batteries should be connected to each other positive to positive and negative to negative. Then attach the charger positive to the positive on one battery and the negative to the negative of the same battery. It will obviously take longer to charge two batteries than it will to charge one. If they are set up to run as 24 volts (wired in series), you will either need to disconnect the jumper wire that connects the two batteries and charge them as two 12 volt batteries or use a 24 volt charger.

  • Why is the fan on all of the time?

    It is normal for the fan to be on all the time in order to keep the transformer and electrical circuitry cool during normal charger use. Keep the area near the charger clear of obstructions to allow the fan to operate efficiently.

  • What is the purpose of the 24” cable and where do I purchase one?

    The 24 inch (61 cm) long 6 gauge (AWG) insulated battery cable referred to in the owner’s manual is for safety purposes. Since the last connection you make to the battery is at the free end of the cable, as far away from the battery as possible, any arcing or sparking will occur away from the explosive gases generated by the battery. As an additional precaution, we also tell you not to face the battery when making this final connection. This cable is a standard battery cable and can be purchased from any auto parts store.

  • Why is my new charger so much lighter than my older unit?

    Our new energy-efficient models are designed with lightweight, high-efficiency transformers.

About Portable Power Units

  • The portable power unit is not charged and I just took it out of the box, is it defective?

    No. Every Portable Power Jump-Pack unit’s battery is fully charged when it leaves our factory. One must factor in the amount of time the unit has spent sitting in warehouses and on store shelves, before it was purchased. The more time a unit sits idle, the greater the decrease in battery power. We recommend charging the battery immediately after purchase, before placing the unit into service.

  • How do I charge my portable power jump-pack?

    Our Portable Power Jump-Packs are manufactured to include an internal charger. A simple household extension cord (18 AWG or larger) is used to power the internal charger. Plug the extension cord into an outlet, and connect the cord into the receptacle on the unit to charge.

  • How often should I re-charge the portable power jump-pack?

    In the Owner’s manual we suggest to charge the internal battery of your Portable Power Jump-Pack immediately after you purchase it, every 30 days and after every use. By frequently charging the battery, you maximize the power potential of the unit, and ensure that whenever you need it, the unit will be ready. Keeping the battery fully-charged also vastly extends the life of the unit.

  • There is no output from the alligator clips of my portable power unit, why?

    One feature that may apply to your unit (IP-1850FL, IP-1875C, and IPD-1800) is a positive connection solenoid. Simply put, the clamps will not arc or spark until being placed on a battery. This feature alleviates arcing and sparking until there is a connection at the battery.

  • What is the jump-starting amp rating on my portable power unit?

    • IP-75: 100CCA / 500 PEAK AMPS
    • IP-95L: 125CCA / 650 PEAK AMPS
    • IP-125: 150CCA / 750 PEAK AMPS
    • IP-1825FL: 300CCA / 950 PEAK AMPS
    • IP-1850FL: 350CCA / 950 PEAK AMPS
    • IP-1875C: 350CCA / 950 PEAK AMPS
    • IPD-1000: 150CCA / 650 PEAK AMPS
    • IPD-1800: 350 CCA / 950 PEAK AMPS
  • 12 Volt DC Power Source Estimated Run Time Chart (in hours)

    Appliance Watts IP-75 IP-95L IP-125 IP-1825FL IP1850FL IP-1875C IPD-1000 IPD-1800
    Cell Phones 4 21 27 36 54 54 54 27 54
    Fluorescent Lights 4 21 27 36 54 54 54 27 54
    Radios 9 8.4 12 16 24 24 24 12 24
    Depth Finders 9 8.4 12 16 24 24 24 12 24
    Fans 9 8.4 12 16 24 24 24 12 24
    Camcorders 15 5.6 7.2 9.6 14.4 14.4 14.4 7.2 14.4
    Spotlights 15 5.6 7.2 9.6 14.4 14.4 14.4 7.2 14.4
    Electric Tools 24 3.5 4.5 6 9 9 9 4.5 9
    Bilge Pumps 24 3.5 4.5 6 9 9 9 4.5 9
    Electric Coolers 48 1.8 2.3 3 4.5 4.5 4.5 2.32 4.5
    Air Compressors 80 1.1 1.4 1.8 2.7 2.7 2.7 1.4 2.7
    Car Vacuums 80 1.1 1.4 1.8 2.7 2.7 2.7 1.4 2.7

    Note: These times are only estimated run times. Variations in products may alter the run times.

  • 110 Volt AC Power Source Chart

    When the Portable Power Jump-Pack is used with an inverter, it can operate appliances normally powered by 110V AC. (Inverter {Not Included} is Necessary).

    Appliance Type Estimated Wattage
    Spot Lights 100
    Sump Pumps 100
    Faxes 150
    TVs 150
    Small Power Tools 150
    Computers 200
    Printers 200
    Power Tools 200
    Blenders 200


About Power Inverters

  • Digital Power Inverter Error Code Explanation Chart

    bAd The inverter is not functional. See warranty and call Customer Service 1-800-621-5485 (Hours: 7:00 am to 5:00 pm CST).
    Hib The vehicle's battery voltage is more than 15.5 volts. The inverter will automatically restart after the voltage drops below 15.5 volts.
    HiP The continuous load demand from the device exceeds the inverter's wattage output. Use a higher rated inverter or a lower rated device.
    Hot The inverter is overheated and automatically turns off for a period of 1-3 minutes to cool. Make sure the inverter is well ventilated. It will automatically restart after it cools.
    Lob The vehicle's battery voltage is less than 10.5 volts. Recharge the vehicle's battery.
    SC There is a short circuit, power surge or overload in the device being powered. Have the device checked.
  • Does my power inverter have to be wired directly to my car battery?

    It depends on the model of the inverter and what you intend to run with it. For electrical loads up to 200 watts, the power-inverter can be plugged into the car’s cigarette lighter. This allows you to power laptop computers, small power tools, most small appliances, and even a small (13") TV directly through the cigarette lighter. If you want to power larger equipment, or if you want to run more than one item at a time, a direct connection to your car battery is necessary. Generally, if you intend to power loads of more than 200 watts, your inverter should be direct-wired to the battery to ensure safe operation.

  • Will using the inverter drain my car battery?

    When using a power inverter, it is always a good idea to turn on the car’s engine every 30 minutes to help maintain your battery's charge. Assuming your battery is fully charged and in good condition, it is possible to use a 400W power inverter for about an hour (not starting your car) without fully discharging your battery. To find how long your battery’s charge will last with any given inverter, use this formula: Take the wattage being used (400W) divided by the battery voltage (12 Volts) to see how many amps are being drawn from the inverter : 400 Watts/12 Volts = 33.33 Amps. Inverters only convert power at around 90% efficiency, so that means the inverter is really drawing around 37 amps (33.33 Amps / .90 = 37 Amps). A typical car battery has a reserve capacity of about 80 minutes (80 minutes @ 25 Amps). So if you are drawing 37 Amps with the 400W inverter it will completely discharge the battery in 54 minutes ((80 minutes * 25 Amps) / 37 amps = 54 minutes).

  • I am getting low or no output voltage from the inverter, why?

    Either you have poor connection at the terminals. Check and clean the 12-volt connections and try again, or you are using an incorrect type of voltmeter to test the output voltage, use a true RMS reading meter.

  • What if the inverter fuse blows?

    Your Schumacher power inverter comes with an input fuse that should not have to be replaced under normal operating circumstances. A blown fuse is usually caused by reverse polarity or a short circuit within the appliance or equipment being operated.

    If the fuse does blow:

    1. Disconnect the appliance or equipment immediately.
    2. Find the source of the problem, and repair it.
    3. Install a new fuse that is the exact same type and rating.

    Attention: Do not install a fuse with a higher rating than the one supplied with the power inverter, as this may damage the inverter. Make sure to correct the cause of the blown fuse before using the inverter again.

  • The red LED on my inverter has turned on, what is happening?

    • When the power input from the vehicle’s battery drops below 11 volts, low battery shutdown occurs and inverter shuts off. Solution: Recharge or Replace the battery.
    • When the power input from the vehicle’s battery exceeds 15-volts, high voltage overload protection occurs. Solution: Reduce the voltage range to between 12-volts and 14-volts.
    • Install a new fuse that is the exact same type and rating.The continuous load demand from the equipment or device being operated exceeds the continuous load rating of the inverter being used. Solution: Use a higher capacity inverter or lower rated device.
    • The case temperature becomes hot (exceeds 145°F). Solution: Allow the inverter to cool. Do not block the cooling slots or air flow over and through the inverter. Reduce the load on the inverter to the continuous rated output.
  • The low battery alarm is constantly on, why?

    • The power input from the vehicle’s battery is below 11 volts. Solution: Recharge or replace the battery.
    • Poor or weak battery condition. Solution: Recharge or replace the battery.
    • Inadequate power being delivered to the inverter or excessive voltage drop. Solution: Check the condition of your cigarette lighter socket. Clean or replace if necessary.
  • I am trying to operate a TV with my inverter, but the TV doesn’t work. What can I do?

    Try turning the inverter ON, then OFF, then ON again. Contact the TV manufacturer for startup surge rating and/or if the TV is compatible with a modified sine wave. An inverter producing a larger power output may be required.