Buck Converter Current Characteristics

That is pretty much how it should work subject, of course, to the efficiency of the converter.

So in practice your 5A @ 17V may work out to a tad less than 10A @ 8.5V.

Just don't let it become too hot. I suspect that your cooling will be inadequate the way you present it.

You must have schematic for the circuit. Ask the manufacturer to give you schematic.

Normally a switching device is used and its frequency components is very important. It required some R and C timing network and then you need to have power diode just after switching transistor / MOSFET.

Buck Converter from Texas Instruments

Also see this DIY

Ok. After having a better look, one of the mosfet shaped things is a 2045CTP schottky rectifier and the other is some form of mosfet shaped switching controller. The part number on that one has been sanded off. On the bottom there is a large surface mount diode with GFK249 on it.

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Question, why would you want to reduce voltage? Those of us in the industry have been relentlessly pushing voltage higher, and converting or inverting to the required voltage for loads, which with solar, rarely coincide with the timing of demand parameters presented by loads. Conductor materials, over current protection and power efficiencies are much more managable at higher voltages.

Your right there. I have had 2 so far that have failed. They had a surface mount controller chip on the bottom and thicker wire with less turns on the inductor.

i donno about how good the circuit unles i get a model no of your 5-pin controller (that's why i call it crap - coz you can't find such listed on their sales site - all i can think of it is poor doc.-n on sales site ?= need to hide(cover up) some shortcomings ???)

anyway what's the point of failure - they specify it as adjustable output voltage - why don't you adjust it to your need (? no doc.-n how to do so) - i attempted to find the chip by specs on their site that're probably copy pasted from buck controller datasheet - with no luck (the google hanged (as usual) so i went offline - did something that can be done in real time - muhahaa)

shortly what's printed on that 5-pin thingy also on any other chip there

i don't want to e-search it anymore - open issues ::
1) the type of your regulator
2) ? input limiting (is it designed for solar array or for 6/12/18/24V battery)
3) is the 5A max/ (also if it(max)'s) continuous/peak output (gained by: as is/additional cooling)
4) design verification (are used components(each of) capable to perform according to design specifications) ...

INSANE:blind gues::
LTC4449
LT1683 unlikely (has 22uH filter)
LT1339
the similar chips may be produced by HTH knows what company - so good luck

First one connected wrongly? Cooling issue?

I have never had them overheat. One just shorted out because I touched the controller chip while it was on. The fuse blew and the whole thing was totally shorted after.

(Super!) how about the LT's paint it book