When setting up a solar system, some say an MPPT charge controller is essential for efficiency, while others think PWM controllers are sufficient for small setups. What’s your take? Have you seen a big difference in energy conversion?"
If the Vmp (Voltage at which the panels deliver maximum power) is not close to the battery voltage, then an MPPT will make a big difference. An MPPT can also get the most out of your PV array in all sorts of non-ideal conditions, such as partial shading, where a PWM controller could do very little. With a PWM controller, the current into the battery can never be higher than the current that the PV array can supply, while an MPPT does a power conversion, so a low current at high voltage in from the PV array can be converted to a higher current at the lower battery voltage.
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From my limited knowledge, I understand a PWM (pulse width modulation) to basically be nothing more than a switch that rapidly opens and closes and brings the panel voltage down to just more than the battery voltage. Charging thus happens at a much lower voltage.
That said, in a small vehicle setup, I have also wondered whether an Mppt really out performs a PWM by that much.
In my case, the MPPT’s max solar input voltage is 22V. I have 2 85W panels connected in parallel, which gives about 18V.
If the battery is at 12 or 13V (Lithium Blue Nova), it really does not give the Mppt much extra volts to work it magic with. That buck converter magic.
But I have it now and don’t worry too much about it because it is a combination unit that gives dc2dc charging also from the alternator (Ctek D250S)
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There is a big difference when the sunlight is weak.
So in summer you don’t need a MPPT but come winter it helps. (I have seen a 30% improvement)
If your load is a battery then you will need a charging circuit which is normally incorporated into the PWM/MPPT.
Thanks stanley i get it now
Thanks swarket , thanks for the clarification
Small addendum I can add. On an African farm, where have a few outstations with lights and noise-makers (an MP3 player and a speaker) that runs from a battery and a solar panel. It keeps predators away from cattle (and, to the conservationist people… yes this means you don’t have to shoot the predator). Because you don’t need a very big solar panel but at the same time a 150W panel tends to be as cheap (if not cheaper) than something smaller, we often end up with panels that are way larger than needed for the application, and as a result, using a PWM controller (even if inefficient) simply doesn’t matter. The cost savings of buying the larger panel and the cheap PWM controller is worth it, and it still works. Or the other way around, if you paid more for the MPPT, the battery would just be full by 9AM instead of 11AM.
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I’ve always said that to get to grips with solar power is like sailing a sailboat.
When the wind is light you hoist bigger sails. Similarly when the sunlight is iffy then you switch in the MPPT…
i get it , i have had similar experiences too