MPPT solar charge controller recommendation?
So I've got some cash now to put into my new to me Lance, and I've decided to build my own 200watt system from scratch rather than purchase an all inclusive kit. I'm going to use cross bar roof rack i...
Forum Discussion
Dak,
Ditto on what the others said. For a 200 watt system, save your money and buy a PWM Charge Controller. I've used the Morningstar Sunsaver Duo in two of my RVs and they've worked great. You'll need to buy 12 volt solar panels when using the PWM CC.
Here's a brief synopsis on the pros and cons of each type of charge controller from my Solar Power 101 article:
Pulse Width Modulation (PWM): A simple, yet time-tested and proven design, the PWM charge controller works by sending a series of short, variable duty cycle charging pulses to the battery--like a very rapid “on-off” switch. The controller constantly checks the state of the battery and automatically adjusts how long the charging pulses will be to the battery. When the battery is fully charged the duty cycle almost falls to zero or "off" nearly 99% of the time. Conversely, when the battery is fully discharged, the pulses of the battery stay "on" nearly 99% of the time.
Strengths of the PWM charge controller design include the fact that it is built on a time-tested and proven technology, is inexpensive--a single unit capable of handling 25 amps can be purchased for less than $100--and is durable. The PWM charge controller comes in various sizes up to 60 amps and can be used in all but the largest systems found in an RV (to give you an idea how large a 60 amp system is, a single 120 watt solar panel produces about 6.5 amps).
While the PWM design is simple and rugged, there are some inherent flaws with the design. For one, PWM charge controllers are less efficient due to the fact that the controller connects the solar panel to the battery directly. This reduces the voltage developed by the solar panel from the nominal 17 volt output to the battery's voltage, which lowers the power available from the solar panel. Another flaw with the design is that the pulses generated by the device can create interference in radios and TVs. This is due to the lower frequencies typically used in PWM charge controllers compared to the higher frequencies used in the MPPT controller.
Maximum Power Point Tracker (MPPT): The newest technology and the latest rage, the MPPT charge controller combines the most effective features of a PWM controller with additional functionality, a PWM controller on steroids, if you will. Instead of connecting the solar panel directly to the battery like a PWM controller, it uses a "buck converter" stage, a DC to DC conversion before the PWM charging stage. The buck converter ingests the solar panel voltage and transforms it to the optimum battery voltage or "Maximum Power Point." Secondly, the MPPT charge controller uses an embedded microprocessor driven algorithm to scan or Track the PV array for where the voltage and current are optimized between the solar panel and the battery (the Tracking portion of Maximum Power Point).
The pros of the MPPT charge controller are pretty significant. It can increase the charging efficiency of the system up to 10% and in some cases even higher. Moreover, the MPPT charge controller is totally compatible with solar panels of various voltages, such as 24 volt and 36 volt models (just make sure all of the solar panel voltages are the same in order for the tracking function to properly work). These higher voltage solar panels can be wired in series or parallel and are generally less expensive per watt than 12 volt models, thus giving you greater flexibility in the panels you can buy. The MPPT charge controller can also be sized up to 80 amps and beyond, providing greater flexibility for system growth.
Cons of the MPPT controller include greater cost, two to four times more to a comparably sized PMW controller, and greater physical size. However, the pros associated with the unit's efficiency and features far outweigh the cons. There's no doubt about it. If you use solar power a significant amount of time throughout the year and cost isn't an issue, then the MPPT controller is the way to go. If your system is used perhaps six to eight times a year, then a PWM controller will more than suffice and provide you with years of excellent service.
Ditto on what the others said. For a 200 watt system, save your money and buy a PWM Charge Controller. I've used the Morningstar Sunsaver Duo in two of my RVs and they've worked great. You'll need to buy 12 volt solar panels when using the PWM CC.
Here's a brief synopsis on the pros and cons of each type of charge controller from my Solar Power 101 article:
Pulse Width Modulation (PWM): A simple, yet time-tested and proven design, the PWM charge controller works by sending a series of short, variable duty cycle charging pulses to the battery--like a very rapid “on-off” switch. The controller constantly checks the state of the battery and automatically adjusts how long the charging pulses will be to the battery. When the battery is fully charged the duty cycle almost falls to zero or "off" nearly 99% of the time. Conversely, when the battery is fully discharged, the pulses of the battery stay "on" nearly 99% of the time.
Strengths of the PWM charge controller design include the fact that it is built on a time-tested and proven technology, is inexpensive--a single unit capable of handling 25 amps can be purchased for less than $100--and is durable. The PWM charge controller comes in various sizes up to 60 amps and can be used in all but the largest systems found in an RV (to give you an idea how large a 60 amp system is, a single 120 watt solar panel produces about 6.5 amps).
While the PWM design is simple and rugged, there are some inherent flaws with the design. For one, PWM charge controllers are less efficient due to the fact that the controller connects the solar panel to the battery directly. This reduces the voltage developed by the solar panel from the nominal 17 volt output to the battery's voltage, which lowers the power available from the solar panel. Another flaw with the design is that the pulses generated by the device can create interference in radios and TVs. This is due to the lower frequencies typically used in PWM charge controllers compared to the higher frequencies used in the MPPT controller.
Maximum Power Point Tracker (MPPT): The newest technology and the latest rage, the MPPT charge controller combines the most effective features of a PWM controller with additional functionality, a PWM controller on steroids, if you will. Instead of connecting the solar panel directly to the battery like a PWM controller, it uses a "buck converter" stage, a DC to DC conversion before the PWM charging stage. The buck converter ingests the solar panel voltage and transforms it to the optimum battery voltage or "Maximum Power Point." Secondly, the MPPT charge controller uses an embedded microprocessor driven algorithm to scan or Track the PV array for where the voltage and current are optimized between the solar panel and the battery (the Tracking portion of Maximum Power Point).
The pros of the MPPT charge controller are pretty significant. It can increase the charging efficiency of the system up to 10% and in some cases even higher. Moreover, the MPPT charge controller is totally compatible with solar panels of various voltages, such as 24 volt and 36 volt models (just make sure all of the solar panel voltages are the same in order for the tracking function to properly work). These higher voltage solar panels can be wired in series or parallel and are generally less expensive per watt than 12 volt models, thus giving you greater flexibility in the panels you can buy. The MPPT charge controller can also be sized up to 80 amps and beyond, providing greater flexibility for system growth.
Cons of the MPPT controller include greater cost, two to four times more to a comparably sized PMW controller, and greater physical size. However, the pros associated with the unit's efficiency and features far outweigh the cons. There's no doubt about it. If you use solar power a significant amount of time throughout the year and cost isn't an issue, then the MPPT controller is the way to go. If your system is used perhaps six to eight times a year, then a PWM controller will more than suffice and provide you with years of excellent service.
