This is another board I got to experiment with after purchasing the 60w Powkey solar wallets. The control chip
is hard-wired to charge 12v lead acid batteries only, and it has a few "configuration resistors" on the board that
define the panel Vmpp, so it's not actually MPPT, despite its markings. But as long as you're connecting it to
18v / 36 cell panels, and are using a lead-acid battery, it should work fine. It's limited to 3 amps to the battery,
but I've seen it go as high as 3.3 amps, so about 40 watts max, which is what I would expect from the Powkey
panels, so they're a good match as long as the battery is lead acid. And given it has no actual tracking, it should
be okay to hook two or more in parallel if necessary, as they won't "fight" each other.
It's just a bare controller board, so you'll have to solder leads to it for the battery and solar. (there's no connection
for "load") It does feature a decent buck regulator, and so is pretty efficient. It's pretty compact, and is a reasonable
deal for the roughly $10 asking price. Don't connect panels with a Voc over 30 volts. The board is also marked
"6v, 9v, 12v, 18v", and the documentation says it's compatible with "6-30v panels", don't expect it to work with
the panels below 12v, since it uses a buck converter that can only step voltage down.
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