Solar Charge Controllers mainly are divided into 2 classes: MPPT and PWM, and you can find the description of the difference between these 2 in the last part of this page.

Both PWM and MPPT charge controllers are widely used in various kinds of solar DC power systems, like solar street light, DC power kit, RV kit, communication DC station, backup power station and so on. Years before, solar DC power products were only being used in industrial projects, and not many people took them for self use, but now more and more people have already accept solar power and begin to use solar products in their personal lives.

If you are interested in solar charge controller, but not a profession in solar DC area, then please read the below content for more understandings:

Safety Use Tips on Solar Charge Controllers

Once you’ve got a solar charge controller, no matter what brand it is, we need to review some tips on charge controller use safety.
  • 1
    Always remember to review the charge controller manual thoroughly before attempting installation. Not only on the electrical parameters parts, but also on the charge controller wiring instruction.
  • 2
    Beware of any nearby electrical equipment that may interfere with installing this device. Solar charge controller is DC appliance, and please never plug in or use it for any AC source.
  • 3
    Solar panels can generate high voltages and currents, make sure your solar panels are completely covered from sunlight during installation. It is recommended that installation be performed by a qualified electrician.
  • 4
    Connecting wires to this device can generate sparks, please wear proper insulation gear while installing this device.
  • 5
    To avoid damage to the battery or controller, use proper fuses in wiring. Please do not hesitate to contact the professions if you need help with fuse sizing.
  • 6
    Always keep children away from this device. If possible, please don’t allow non-professions to touch this device or the whole system.
  • 7
    Be certain to use the correct gauge of wire, see below for a table of recommended wire size for various current loads.
Solar Input Current 5A 10A 20A 30A 40A 60A
Wire SIZE (mm²) 1.5 2.5 5 8 10 12
Wire AWG 15 13 10 8 7 6

Safety Use Tips on Solar Charge Controllers

If you are now using a HeliosNE charge controller, then sometimes you may find some error code may appear in the LCD screen. That means there is something wrong with the system, and we need to check and do the quick trouble shootings as what in the below diagram:
Error Description & Quick Troubleshoot
Battery Over-discharged Battery Over-discharged Battery voltage is too low. DC load will be turned off until battery re-charges to recovery voltage.
Battery Over-voltage Battery voltage has exceeded controller limit. Check battery bank voltage for compatibility with controller.
Load Short Circuit DC load short circuit.
Load Overload DC load power draw exceeds controller capability. Reduce load size or upgrade to a higher load capacity controller.
Overheating Controller exceeds operating temperature limit. Ensure the controller is placed in a well-ventilated cool, dry place.
Solar Over-amperage Solar array amperage exceeds controller rated input amperage. Decrease the amperage of solar panels connected to the controller or upgrade to a higher rated controller.
Solar Over-voltage Solar array voltage exceeds controller rated input voltage. Decrease the voltage of solar panels connected to the controller.
Solar Reverse Polarity Solar array input wires connected with reverse polarity. Disconnect and re-connect with correct wire polarity.
Battery Reverse Polarity Battery connection wires connected with reverse polarity. Disconnect and re-connect with correct wire polarity.
For further questions, or you need to talk with our engineers, then please email us or leave messages in the website.

Charge Controller Basic Knowledge FAQ

  • 1.What’s the difference between PWM and MPPT charge?

    PWM and MPPT are 2 main ways for solar DC charge to the battery.

    PWM, short for Pulse Width Modulation, is a technology to use a certain part of voltage from the PV modules, to charge according to the battery actual voltage. For example, if we use a 18V solar panel, to charge a 12V battery bank by a PWM controller, and supposed the battery now is on voltage of 12.8V, then PWM controller would take 12.8V from the panel to charge, but this voltage would change when the battery voltage changes, so we may also lose the part of PV voltage above the battery value. That’s why we always say PWM is lower in charge efficiency, and commonly we may have a rate of 70-80% as the PWM charge efficiency. Please notice that if you use 30 or 36V PV module to charge the 12V battery bank, then most of the PV voltages would be wasted because normally no higher than 16V PV voltage would be used for PWM charge on 12V battery system.

    MPPT, short for Maximum Power Point Track, is a technology to track and use most of the PV power to charge the battery. There are several kinds of MPPT tracking methods, but all are leading to make full use of solar power. The difference is about the adjustment of the MPPT technology to different applications. As you can see, MPPT is to try to make full use of PV power, and this is the biggest advantage over the PWM. Considering of the unavoidable power loss, the MPPT charge efficiency is supposed to be over 95% averagely, and could be up to 98% in the peak time.

  • 2.How to choose PWM or MPPT controller for my solar DC power system?

    Many solar power system users may have headache about how to choose a controller for their solar power systems, PWM or MPPT? Commonly, we have a few guidelines for this:

    • 1) If your system is very small, like PV lower than 100W, PWM may be better. However, if you system has a high demand on charge amount, you also can choose MPPT, like some solar light with high LED power.
    • 2) If your PV array’s voltage is much higher than the battery bank, like 12V battery, but 30V PV system, then no doubt you need to use MPPT. Almost all thin film PV arrays (very high voltage) have to use MPPT.
    • 3) If you use Sun Power cells assembled modules, then it’s better to use MPPT.
    • 4) If your PV module voltage is very close to the battery voltage, like 30V module to a 24V battery bank, or 18V module to a 14.8V lithium battery, PWM charge may have an improved charge efficiency, sometime could be up to 90%. * please notice that the PV voltage shouldn’t be lower than the battery charge voltage all the time while it’s working.
    • 5) If the PV voltage is very close to the battery bank voltage, then MPPT may not work very well, and in some cases like that, MPPT charge may never begin in the whole charge time.
    • 6) If you still have no idea about how to choose, then please contact us.
  • 3.How to make the best and safe use of MPPT charge?

    Firstly, MPPT charge starts only if the PV with a voltage difference higher than the battery. Usually this voltage difference should be higher than 3V at least.

    Secondly, all MPPT device may have a limit on max input voltage. For example, Helios’s MPPT controller VENUS-M2440 with a max input of 100Voc, so this 100Voc (PV open circuit voltage, not rated voltage or working voltage) is the limit, and you can not plug in arrays over this limit. * usually 100Voc means 75V around of working voltage.

    Thirdly, if the voltage difference between the battery and PV is too much, then we may have a not small power loss, so we need to control the array voltage by connection more parallel and less series on panels. For example, for controller VENUS-M2440 (12/24V), if you have 2 panels of 36V, then it’s better to make them connect in parallel (36V), but not in series (72V).
    However, it’s not really a big deal, the difference could be very small. If you find it’s not convenient to make the modules connected in parallel, then just do it by series.

  • 4.How to find and fix the problems with solar DC power system?

    No solar power system can be perfect for all time, so we need to know how to fix the problems if we find any.

    Firstly, anytime if we find the solar charge controller works no good, we should go to check the LCD display for the error code. And then we find the user manual and check the corresponding explanation and follow the suggestions to debug it. If the controller has no screen, then try to check the status of the LED indicators. Please don’t threw away the controller manual. It is very important when you have problems with your power system.

    The most common error we can find is battery over discharge. When PV plugs in the system, the battery voltage would be pulled up from some, higher than what it actually is. Therefore, if the battery has no much capacity remained, and the weather is not so good (no much charge in the day time), the controller may give the error signal of over discharge, in a short time after the PV is off in the night time. It is easy to solve out this problem, just to keep the battery in charge, and the error code would be gone after the battery being charged to the over discharge recovery voltage.

    Some problems could happen in controller setting operation, especially when user trying to set non-default voltages value in the controller, but not familiar with the setting method. For this part, if you made a mistake or not sure if you had made any, just try to set the controller back to the default mode, and everything would be to okay status.

    At last, the best way has always been that to contact us, the professions for advises.


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