mppt vs pwm

ewarnerusa wrote:
Thanks Salvo. I've read through the manual many times. And while I think I understand it, I read forum threads like this one and I second guess what I think I know. But the manual says it tapers the current down while holding the voltage constant when in absorption mode. This is unlike how I'm understanding on/off shunt controllers which just toggle the full panel current on and off.

The on/off method is called "Shunt-interrupting" which goes between two voltage set points.

The newer method where voltage is held while amps taper is called "Series-interrupting" (this short circuits the panel to interrupt current) The Series method is also called "PWM"

In retaliation, when that came out, the Shunt people at the time like Specialty Concepts with their Shunt controllers (Automatic Sequencing Controller or ASC) started to call their controllers " Low Frequency PWM"

In fact the newer Shunt ASC types did not go between an low and high set-point. They did do on and off, but also there was pulse width
so as the battery rose in SOC the length of the time it was on got less and the length of the time it was off got more when it was on or off. Both voltage and amps went up and down to make you dizzy.

In response to that, AM Solar (Greg somebody ISTR) about 10 years ago came out with a sneering report that this old style Shunt method (ignoring the latest pulse width thing) was not really "PWM" and was just marketing language. Meantime AM Solar was pushing for everybody to get the "newest thing" which was their new MPPT controller :) And so it goes.

Shunt types were eg, SCI mark 15, ICP Solar PRO. Series PWMs were Heliotrope RV-30SE eg, and the latest thing to replace all those was the MPPT HPV-22.

My first controller was an ASC shunt type with the pulse length trick. That worked great. Next was an EP Solar Series type that tapered the amps during Absorption but I would not be able to say they were any different really. Worked great too. Perhaps the Series is a bit smoother than the Shunt with pulse length during Absorption if that matters to anybody. I doubt the batteries care.

I now see that the MPPT Tracer by EP Solar has the same charging profile as their Series PWM LandStar controllers. (and the same diagram of that and the exact same word for word blurb on that is in the MorningStar manuals