Right now mppt controller pricing looks something like this, using 10A as an example:
Premium like Morningstar $200 Standard like Victron $100 Cheap like Epsolar/Tracer/Renogy $50 Ultracheap no-name from China $25
I use the cheap stuff, but would use premium if I had the cash. I am interested in ultracheap to see what is possible, and for what they might bring to the ‘dwellers who are “least among us”.
Adam Welch buys and reviews all kinds of solar gear on his YT channel. One of his finds was an actual MPPT for about $50, the CPY-2410. Unfortunately, later versions are dumbed/cheaped down and aren’t doing MPPT that most of us would recognize.
Blogger finophile has written some articles on these newer version[s] of the controller.
Here is my comment on one of them, slightly formatted and with a line or two added:
I've ordered one but haven't received it yet. I _am_ convinced the unit does DC-DC conversion (explaining current gains). I am _less convinced_ it is doing MPPT in the normal sense. A much cruder algorithm that would line up with both your and Adam's observations might look like this: 1. detect Voc 2. guess at Vmp based on a common correlation: Voc x .8. This is a common starting point in more refined MPPT algos, which use it as a starting point. A crude MPPT algo would use it as a "good enough" ~Vmp. 3. run the panels at ~Vmp and DC/DC downconvert until battery reaches a given setpoint 4. then run the panels at Vbatt + 2v and and DC/DC downconvert. PWM or shunt to stay at the setpoint. I don't have a problem with that kind of setup, particularly if they > > > * add in configurable setpoints > > * reliably restart the algo when battery voltage falls > > * keep the price down to about $25 shipped from CN > > * be honest about what it's doing. Heck, I'd market it as value added feature. "Simpler algo saves you money and still gives more power than PWM!" > I have no explanation about why the unit responds to loads on the LOAD output but not on the battery itself, but if it's happening then it's happening. Hard to disagree with empirical testing. When I get mine I'll test that, and also test if it acts the same when the LOAD draw is light, as when using a relay from LOAD to control inverters and other non-trivial loads.
When mine gets here I will test it to see if my guess above has any merit.