MtnDon
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# Posted: 7 Feb 2015 21:40 - Edited by: MtnDon
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All MPPT output in PWM form. PWM is simply a method of controlling the output voltage. FYI, the electronics turn the power off and on hundreds or thousands of times per second. These are pulses; that is the "P". The "W" is the width of the pulse (the length in time). The "M" is modulation or adjusting. The "W" is where the power is turned off and on. The pulse width remains constant. The power can be turned on for a portion of the pulse, maybe 40% of the width or time of that pulse. The rest of that pulse has the power turned off. To make the voltage rise higher than that, the on time is increased to maybe 70%. When that happens the off time is shortened to 30% of the time. The total of the on time and the off time is always equal to the pulse width.
Sort of like turning a light switch on-off and making the on and the off intervals always add up to the same width of pulse, like 10 seconds. ... 4 seconds on, must then have 6 seconds off. The difference is that PWM measures those total intervals, pulses, in very short times. 400 or maybe 1500 per second.
PWM can only control, or adjust, voltage. In a plain PWM controller the voltage is adjusted down to suit the battery but the amps remain the same going out as coming in.
MPPT technology changes voltage/current to best suit what is coming in from the PV and what the present state of charge of the batteries are and therefore what can be put into the batteries.
MPPT is the ability of the controller to take high incoming voltages and transform them down to what the battery can best use, while adjusting the current up,something the straight PWM can not do.
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