[SOLVED] Ideal Buck converter for solar to USB


I'm planning to use a 12v (20W) solar panel to power my Arduino Digispark. Since the Arduino doesn't need all that power, I have decided to use the remaining power to charge a USB power bank (5V 2A input). The Arduino only powers an LED ~20mA at the moment.

I came across 3 different types of cheap Chinese buck converters to convert 12V to 5V(LM2596, XL4005 and XL4015) , I do not know which one to choose and need your advice to decide which one should I buy. :confused:

Each module shows different switching frequency in their chip datasheet( I don't know anything about that ). LM2596 150KHz, XL4005 300KHz, XL4015 180KHz. Will this affect my project? Also each module has different max input current, LM2596 has 3A max and both the others have 5A max.

Also, Can these modules run without a heat sink in an enclosure without vents ( climate is tropical usually always above 30C and humidity above 70%)?

Just make sure, that the input and output voltage, and the current capabilities are correct. Note that the output voltage of a 12V solar module can be higher than 12V, so your buck converter should be resistant to input voltages up to, let's say 20V.

Don't worry about the switching frequency, if doesn't matter to you.

Edit: This should do the job

lg, couka

All the modules I mentioned are capable of handling voltages up to 30v and converting them down to 5v.
The problem I saw was that their current capabilities were different. LM2596 says 3A whereas the other 2 says 5A. Will these modules explode if the input current is very high, even though the draw will be just 11 or 12 watts?

I am asking this because i saw a Russian guy doing some testing and this 5A XL4005 module exploded within a few seconds. I did not understand what he said or did, but I get the idea that these modules are not exactly as what they mentioned. :confused:

I initially considered your Kis3r33s module but the internals looked really really tiny and I thought that those tiny chip and inductor won’t handle much current. ( I may be wrong )

Well, it’s rated 3A and your solar panel won’t output more than that.

The guy in the video shorted the module. The highest reading I saw on the current clamp was over 17A! No wonder the poor thing gave up and exploded within seconds.

If you feel more safe with an 5A module, there’s nothing wrong about using it, though :slight_smile:

lg, couka

Shorted or supplied more current than needed? and 17Amps :o …

I’m asking should I go with the 5A XL4005 is because in LM2596 module they say 3A and max 4A if used with heat sink. Both XL4005 and XL4015 says 5A and max 7A with heat sink.
My concern is that I’m planning to place these converters inside a small project enclosure box that has no vents for air circulation. So if the temperature rises inside the box will the efficiency of the 3A unit decrease? or maybe explode? :confused:

Noobian: Shorted or supplied more current than needed? and 17Amps :o ...


I think you are worrying a bit too much. 20W/12V means you are expecting 1.7A and that's the theoretical maximum the solar module can deliver under perfect conditions.

You can just add a 2A fuse between solar module and buck converter if you are really that worried. Unnecessary though.

lg, couka

Oh ok, Thanks for the advice . :)