Ready to get my feet wet with Solar power
Thought I would post my idea here and let the experts tell me what I am missing. First off, I own 2ea RV's. 1 is a gooseneck horse trailer with living quarters and the other is a bumper pull prowler....
Forum Discussion
Regarding PWM and MPPT controllers and my pre-determined reasoning for using an MPPT controller: below are comments made by 2 different people regarding these controllers on a different forum.
Quote person 1: You can have MPPT and PWM controllers that can handle 12V, 24V, 48V panels.
The difference between the two is the internal operation of the controller. The MPPT controller will adjust the panel voltage to ensure maximum power extraction, whereas the PWM controller operates at the battery voltage. MPPT controllers will give about 10%-30% more power from a given panel over the course of a day, because they account for changes in the optimum panel voltage due to temperature and other factors.
In a PWM controller, the extra power isn't necessarily burned in the controller, it is never seen, because the panel isn't being operated at the best point. i.e. if a PWM controller decided to operate the panel at its open circuit voltage, the panel would output zero power, and the PWM controller would handle zero power, regardless of how much power the panel has the potential output.
Quote person 2: With an MPPT controller depending on the manufacture you can run the solar panel Voc up to 150 volts to charge a 12 volt battery system.
The main advantage of using a MPPT is overall efficiency and it comes from 2 reasons. Running higher voltages means running lower current for a given wattage. Lower current means much lower wire losses between the panel and controller. Eaxample say you have a 500 watt array. With standard 18 volt panels used in 12 volt battery systems means you are running close to 30 amps current. Well if you use the minimum size wire for 30 amps like most folks of 10 AWG over a 1-way distance of say 40 feet, you loose about 40 watts of power. That is almost 10 % of your power.
With the same setup using say 100 volts you are running 5 amps and can use a smaller less expensive wire of 14 AWG over 40 feet and loose only around 10 watts.
However wire losses are not the big loss, it is the controller loss that bites. With any shunt type controller the minimum power loss is 25% up to 40%. Or in other words 60 to 75 % efficient. That is a huge loss. MPPT efficiencies run as high as 97% and average 94%.
So controller selection matters. It is not so important in smaller systems because of th ecost involved. But when you jump up in power levels, it pays to use the higher priced MPPT charge controllers. You will not need as many panels and it pays for itself upon installation.
Quote person 1: You can have MPPT and PWM controllers that can handle 12V, 24V, 48V panels.
The difference between the two is the internal operation of the controller. The MPPT controller will adjust the panel voltage to ensure maximum power extraction, whereas the PWM controller operates at the battery voltage. MPPT controllers will give about 10%-30% more power from a given panel over the course of a day, because they account for changes in the optimum panel voltage due to temperature and other factors.
In a PWM controller, the extra power isn't necessarily burned in the controller, it is never seen, because the panel isn't being operated at the best point. i.e. if a PWM controller decided to operate the panel at its open circuit voltage, the panel would output zero power, and the PWM controller would handle zero power, regardless of how much power the panel has the potential output.
Quote person 2: With an MPPT controller depending on the manufacture you can run the solar panel Voc up to 150 volts to charge a 12 volt battery system.
The main advantage of using a MPPT is overall efficiency and it comes from 2 reasons. Running higher voltages means running lower current for a given wattage. Lower current means much lower wire losses between the panel and controller. Eaxample say you have a 500 watt array. With standard 18 volt panels used in 12 volt battery systems means you are running close to 30 amps current. Well if you use the minimum size wire for 30 amps like most folks of 10 AWG over a 1-way distance of say 40 feet, you loose about 40 watts of power. That is almost 10 % of your power.
With the same setup using say 100 volts you are running 5 amps and can use a smaller less expensive wire of 14 AWG over 40 feet and loose only around 10 watts.
However wire losses are not the big loss, it is the controller loss that bites. With any shunt type controller the minimum power loss is 25% up to 40%. Or in other words 60 to 75 % efficient. That is a huge loss. MPPT efficiencies run as high as 97% and average 94%.
So controller selection matters. It is not so important in smaller systems because of th ecost involved. But when you jump up in power levels, it pays to use the higher priced MPPT charge controllers. You will not need as many panels and it pays for itself upon installation.
