These days ready-to-use DC-DC converters are everywhere, with some of the cheaper ones even being safe to use without an immediate risk to life and limb(s). This piques one’s curiosity when browsing various online shopping platforms that are quite literally flooded with e.g. QS-4884CCCV-1800W clones of a DC-DC boost converter. Do they really manage 1800 Watt even without active cooling? Are they perhaps a good deal? These were some of the questions that [Josh] over at the [Signal Drift] channel set out to answer.
The only real ‘datasheet’ for this module seems to come courtesy of a Floridian company who also calls it the 36843-PS, but it features specifications that are repeated across store listings so it might as well by the official ‘datasheet’. This module is marketed as being designed for the charging of lead-acid and similar batteries, including the boosting of PV solar panel outputs, though you’d really want to use an MPPT charger for that.
With this use case in mind, it’s probably no surprise to see on the oscilloscope shots under load that it has a tragic 100 kHz switching frequency and a peak-to-peak noise on the output of somewhere between 1-7 VDC depending on the load. Clearly this output voltage was not meant for delicate electronics.
Looking closer at the board, we can see that it features a TI TL494C as the PWM controller IC, which drives the MOSFETs that form the boost circuit. There’s also an XLSemi XL7005A buck converter that is used for the low-voltage supply on the board. Meanwhile an LM358 dual opamp seems to be used in the voltage monitoring circuit, which also completes the analysis minus the passives, the MOSFETs for the buck (IRFB3206) and boost (IRFP4468) circuits, and a 100V-rated Power Schottky rectifier.
While the board does implement some basic voltage- and current-related safeties and limits, even the documentation tells you to not leave it powered on for too long. As for pushing it to the full 1,800 Watt output, this would require at least 48 VDC input, enabling e.g. 90 VDC output at 20A. Since the input terminal is only rated for 300V at 30A, the input for the subsequent stress test was limited to 48V at 30A for a total of 1,440 Watt from three 48V PSUs.
Using two resistive heating elements as a ~1,800 Watt load the output of the module was measured to see how far the module can be pushed. This turned out to be 1,200 Watt with the 48VDC input proving to be the limit. With the maximum 60VDC input you may be able to provide the current required to hit the full 1,800 Watt, but at that point you’re pretty close to the output voltage anyway. This makes a total of 500-1,000 Watt more reasonable.
Considering the overall performance, the original listed application as a battery charger seems to be about right, with a very barebones design. Its output switching noise and lack of safeties, as well as inability to fully turn off, mean that it should not be used by itself for anything that will be powered for extended periods of time, nor should anything sensitive to switching noise be exposed to its output voltage. For the $18 or so that this module goes for on certain popular platforms one could do much worse if you know what you’re doing.
Funny. I got the identical module a few weeks ago and I just completed its characterization yesterday. My application is charging a LFP battery bank’s “solar” (MPPT) input from my car alternator.
From the claimed specs, I assumed it would pass 1800 W only at 60 V input (i.e. 30 amps maximum input), and only for a little while. I fully expected it to accept 25 amps input indefinitely with sufficient cooling.
I only have 11-15V input from the car, so expected to get 300-400 watts out. The MPPT input to the LFP battery happily accepts 12-60 V at up to 20 A, so I just needed to find the best voltage to maximize power transfer and/or efficiency.
Upshot: This thing will put out more than 450 watts at 12.5 V input, 45 V out, but it gets pretty toasty pretty fast: the efficiency is only 80%. The capacitors take the brunt: they hit 100 C (!!). They are crappy cheap caps with high ESR.
I doubled the input and output capacitance with low-ESR caps which dramatically improved their temperature.
I’m getting 91% efficiency at 38 volts, 8.5 amps = 320 watts output. Input is 12.7 volts, 28 amps input.
I packaged it up for vehicle use and it has literally run all day like this, with the heatsink and caps running at 37 C. It’s a keeper.
TL494? That’s an oldie. I once hacked a PC supply and that was the chip in it…20 years ago!
The design for this board is probably about that old, I’d reckon. It seems to be a ‘good enough’ design that works well with this very common controller IC, ergo everyone keeps using it :)
the TI datasheet is from January 1983 ..
I couldn’t find any of these at Toshi Station
You can waste time with your friends when your chores are done. Now, come on, get to it!
“Since the input terminal is only rated for 300V at 30A, the input for the subsequent stress test was limited to 48V at 30A for a total of 1,440 Watt from three 48 Watt PSUs.”
Shouldn’t that be “three 48 Volt PSUs.”?
Yes, I think someone copy/paste from the auto subs from the video where the same error occured while the guy clearly said 48V and not 48W.
I jot down notes purely by ear/eye when I watch these videos for a summary. I do not use any subtitles/transcription/’AI’ summary unless forced to.
All I can offer as explanation is that I got my units crossed while transcribing while watching the video. Guess I’m only human.
Regular wall socket only goes to 220V so it’s actually pretty useless for modern homes. You need a specialized generator to make 300V electricity.
Certainly.
The first part of the sentence also has a typo obviously, 300V at 30A is 9kW.
Sure, if you can input 300V, but the input voltage here is 48V, and the 30A limit remains, as does the maximum input voltage for the boost IC.
It should be, yes. Thanks for catching that glitch :)
With some decisive hoaxing it should deliver 1.21 jigawatts no problem.
May need flux capacitors instead of the ordinary electrolytic ones, which means it could also go both ways simultaneously, back to the future and forward to the past.
(waving a flag with “DRY CAPACITOR HUMOR” written in the largest fonts possible).
Given the recent trend on this platform, it seems appropriate to give positive feedback to a positive effort. I for one give you two thumbs up! I got a charge out of your joke…
;-)