D-PLANET [2-Pack] Adjustable DC-DC Buck Boost Converter Automatic Wide Voltage Regulator XL6009 DC to DC 5-32 V to 1.25-35 V Voltage Module

I have an old Extech Multiscope multimeter that doubles as a (very bad) oscilloscope. I keep it around mostly because it fits in a tool bag and is useful for looking at voltage/current waveforms at mains voltages (120+ volts). It gets dragged out when I fire up a generator to check voltage and frequency, for example. Yeah, there's better tools for this but it cost me almost nothing, so... One thing it does really well is kill batteries. Extech knew this and placed a 9V power jack on the side of the beast so you can power it from a wall plug. If you use rechargeable batteries in it, you can also charge them without removing them from the meter. Except... it doesn't work. A 9V charger is barely enough to get the LCD to display a reading, and it sure won't charge batteries. I used a variable power supply to determine that it needs around 10.5V to actually work (at least mine does). The cheapest way to make that happen was to cut the cord on a generic 9V wall charger, wire this buck/boost converter in series, and shrink-wrap the whole mess back up. This took less than 15 minutes to do. I set the output voltage for 10.5V and plugged it in. The meter works perfectly on this. The charge cord now has a big lump in the middle of it where the boost converter is wired. I have to be careful not to throw the charger around too much or get it snagged on something for fear of ripping the wires loose. Since I only use the charger when the meter is on the bench, this is no big deal. The converter worked out of the box and I have a second one just waiting for another project.

Terrible. Only one of the 3 i purchased actually worked. 2 won't output the correct voltage once set. Set it to 3.7v and it still outputs the same as the supply voltage.

I am going to be using these to power an Arduino and automotive sensors. I set one to 8.25 volts to power the Arduino using my bench power supply. I can power it on and off and my Fluke MM always reports the set voltage. The second one I'm using to power automotive sensors. I set that one to 4.9998 volts using my Keysight bench MM and every time I turn the power off and on, it reports the same output voltage. Got to love 4 digit stable voltages.

I've had this module connected to my 12V bench supply for a few hours now and can only adjust the output from 12V to over 30V, but not down to 9V where I need it. Not sure what I'm doing wrong, but it seems to be a boost module, not a buck!

Handy little regulator. As other posters noted, if you draw too much current without heatsinking it properly you'll regret it. Note the limiting factor isn't the switcher IC, it's the diode next to the output filter. It only has 3A absolute max rating. And is that a series ceramic cap? If you run it near its max I'd put a big heatsink on the back as well as on the switcher IC, that should help the diode do what it can. Also pay very close attention to your input voltage, as another commenter noted if it drops under spec the converter can suddenly shut down causing the boost inductor to spike. The zener he suggested sounds like a good idea though I would use a higher value for more margin. A nice plus on this module is mounting holes. Many competing modules don't have any. Overall it's a good module for the price but pay attention to its specs.