Shortly after writing the above post, doing some more experimenting, I wound up smoking my new voltage bucker by allowing the output alligator clamps to touch each other when testing the newly arrived wattmeters accuracy at different loads. Not sure if it also smoked the new Jaro fan which was the load, I had to walk away at that point.
I am going to copy/paste a post I made in the 'releasing the magic smoke' thread.
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What gets me all fired up about this, is I set up some alligator clamps so I could easily hook and unhook leds and fans. I actually made some up specifically for doing this. Usually I slide some large heatshrink over them and just shrink the one side so they cannot slide off the end of the alligator clip and keep them from touching each other.
But the heatshrink I had remaining was just tight enough in inner diameter, that the clamps would not fully clamp down on 22 awg wire with it slid over. So I used a separator in between the fairly stiff 14 awg output wires instead to keep them apart. I fired up a powerful 120 fan at full voltage output, without the 4 Lb lead fishing weight atop keeping it in place, and it sucked itself backwards and ripped out the separator and the alligator clamps touched, and that was all she wrote.
But the cursing had just begun. Hope the fan is not fried too.
I gave up testing and experimenting at that point and went and assured Fiona I was not yelling at her.
I liked that specific voltage bucker, it had a current potentiometer that worked as well as the voltage potentiometer for dimming 11 powerful leds, but would allow them to dim even further, and the 40mm fan I have on the same circuit cooling the leds would not come to a standstill at sub 4 volts on the current pot, but would on the voltage pot.
It did not whine at reduced speeds on either pot, like it does horribly on the 13khz PWM LED dimmer.
This specific bucker was only dropping 0.3v at 2 amps of load, so 12.8 in and cranked all the way up, 12.5 out.
Later on I was cleaning my workshop and found 3 older 3 amp buckers with the older LM2596 chip where the newer 5amp buckers have the XL4015 chip.
The smoked bucker had this newer chip. I forget how much the LM2596 drops, but will check soon.
I have employed several of these PWM dimmers years ago, and now some of the lights are now flickering when dimmed, which 'might' be potentiometer related, but perhaps magic electronics related. Me thinks the voltage buckers will take over the LED PWM dimmer duty, as 0.3 drop from battery voltage is not significantly dimmer and ~92% conversion efficiency is not going to kill my battery measurably sooner.
I wonder If Fiona can hear the LEDs whine when dimmed. I have had some which I could hear when dimmed via 13khz pwm dimmer, but I no longer employ those bulbs. I think 180KHZ is above her ability to hear.
Here is a link to the older 2596 3 amp voltage bucker. There are other sellers even less expensive, but this link has very good pictures.
https://www.ebay.com/itm/20V-12-5-3-LM25...0008.m2219
Here is the newer 5 amp bucker I employ on my 7500 rpm 92mm delta fans:
https://www.ebay.com/itm/20V-12-5-3-LM25...0008.m2219
Here is the voltage bucker with XL4015 5 amp chip that also has a current adjusting potentiometer, the one I smoked today:
https://www.amazon.com/DROK-DC-DC4-5-30V...FVKCZHBSK7
There are many variations of these devices on ebay and amazon, some come with voltmeters and ammeters, and pushbutton voltage/current adjustments. I find the prices to be kind of amazing.
Here are two of the older 3 amp models, 2 for a dollar with free shipping:
https://www.ebay.com/itm/2X-LM2596-DC-DC...0667.m2042
Trying to buy the lm2596 chip by itself is more expensive. So is the sticky backed individual heatsinks.
It should be noted that if one is going to approach the max amperage of these devices they should have a small heatsink added to the 2596 or 4015 chips. The 5 amp link above shows a black finned heatsink added to the chip in the one pic. I hope they provide them, but if not I had bought some thicker copper ones for my 2596 buckers on my older 154 cfm delta fan. where the newer delta fan is over 3 amps and 175cfm.
I still have my very first LM2596 bucker that I used n the Silverstone AP182 fan. At battery charging voltages at max speed the hub would get too hot, stinky plastic hot, so I limited it to a maximum of 11 volts, and the fan lasted about 1.5 years, failing likely due to corrosion on circuit board from sucking in salty humid air. The bucker still works. that fan is about 1.2 amps at 11 volts at max speed and I never added a heatsink to it.
I have not had one of the voltage buckers fail, other than those that I reversed the polarity on, or touched the output leads together.
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