Calling on Solar Techies
I have been thinking of going solar for some time and decided to pull the plug. My wants are a 400 to 500 watt system. I have four 12 volt batteries with 340ah. I am not planning on changing b...
Forum Discussion
Ok,
In simple english. MPPT takes the "extra" voltage from the panel, changes it to pulse dc (or is it ac at that point?), transforms it down in voltage and delivers more amps out, than amps in. While doing so, it has an overhead (loss) of about 4%.
PWM does nothing with the extra voltage so that is "wasted" power.
The most famous example of MPPT was a unit called "heliotrope" It worked so poorly that it consumed more power doing MPPT than it produced. The unit was heavily marketed by AM Solar. It was the early days of MPPT at the consumer level.
Does MPPT work better than PWM and harvest more watts? The answer is a resounding "It depend". Often it does. But sometimes, it does not.
If you want to go MPPT, then go high voltage on the panel side, the higher the better so long as you don't exceed the input voltage. The trade off is the higher the voltage, the more loss at the charge controller. But the higher the voltage, the earlier and later in the day charging will be presented to our ever hungry batteries.
If you want PWM then go with panels that do around about 19 volts (plus or minus 2 volts).
What ever choice you make--enjoy having the nearest thing to a free lunch you are likely to find for as long as you have the system. Mine is now 15 years old and still producing its rated output. I'm as happy as a clam--even if it is rather small by today's standards.
In simple english. MPPT takes the "extra" voltage from the panel, changes it to pulse dc (or is it ac at that point?), transforms it down in voltage and delivers more amps out, than amps in. While doing so, it has an overhead (loss) of about 4%.
PWM does nothing with the extra voltage so that is "wasted" power.
The most famous example of MPPT was a unit called "heliotrope" It worked so poorly that it consumed more power doing MPPT than it produced. The unit was heavily marketed by AM Solar. It was the early days of MPPT at the consumer level.
Does MPPT work better than PWM and harvest more watts? The answer is a resounding "It depend". Often it does. But sometimes, it does not.
If you want to go MPPT, then go high voltage on the panel side, the higher the better so long as you don't exceed the input voltage. The trade off is the higher the voltage, the more loss at the charge controller. But the higher the voltage, the earlier and later in the day charging will be presented to our ever hungry batteries.
If you want PWM then go with panels that do around about 19 volts (plus or minus 2 volts).
What ever choice you make--enjoy having the nearest thing to a free lunch you are likely to find for as long as you have the system. Mine is now 15 years old and still producing its rated output. I'm as happy as a clam--even if it is rather small by today's standards.
