mr.jbThe RT8272 looks very promising ( especially with a 22uF cap at Vin ), so far it has no problem charging with my smallest 0.2A to my largest 1.5 A solar panel ( with clouds or clear blue sky ).
http://tw.richtek.com/assets/product_file/RT8272/DS8272-02.pdf
Veery cheap
With a big cap at Vin I think it is regulating around under-voltage lockout ( 4.2V ) when it's cloudy
http://www.fieldlines.com/index.php/topic,144628.msg977808.html#msg977808
This might be taken one step further with the EN pin.....( if it's worth the trouble ). The under voltage lockout is close to the Mppt point for smaller "5V" panels.
But I think it's use should be limited to one panel ( <= 1.5 A )...
Putting several RT8272 in parallel is probably not a good idea since Vref "0.92v" (FB) will differ from circuit to circuit, meaning one circuit will probably get more heated than the others.
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I bought 5 of these, and I don't know what went wrong, but 4 out of 5 ended up dead, right during testing! Either giving 0V, or letting through Vin, or not changing Vout, no matter what, or just overheating -- one even exploded in my hand! :-ooo
Do you need to be careful with anything non-obvious? Mandatory load, EN pin not floating, anything? Strange. I haven't had any problems with other power supply modules so far.
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I blew up at least 8 modules RT8272. An indication of the issue is described in https://www.eevblog.com/forum/beginners/my-smps-design-keeps-blowing-up/.
My guess is that the input capacitor has a very low ESR causing transients. My 15V step input caused a 35.2V peak voltage on the input which damages the IC with a 24V input voltage. A 100uf 25V Aluminum Electrolytic Capacitor reduced the transient to 17.2V.
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