So I have purchased a few power supplies and it seems like that there is a large voltage sag at higher amperage levels. So if I could get some recommendations for one that would keep a constant voltage 4.2 volts 20 amps. Adjustable voltage to 15 volts 20 amps.
I also consider buying a PSU and I have similar requirements (though I want 0-38V at least).
I see people recommending RD Tech, HKJ among them. And there is a suitable model, DPS5020
You can find a few reviews of it here on BLF.
Though for it I need a constant voltage PSU, at least 48V 20A PSU.
Any recommendations?
Currently i am looking for the RDtech 6006 which looks nice.
Not sure whether it is able to read up to 20A
No, it’s merely 6A.
BTW, I see that there’s a custom firmware for DPS series PSUs:
Many budget power supplies go to 6 or 10A, not so many go to 20A, they tend to be a bit more expensive too.
OK, maybe by being frugal with my requirement I can save some?
I see that RDTech recommends a PSU that’s 60V (lowered to 56V by the seller), 20A, $110 + $70 shipping.
Too much. 
At minimum I want to:
- drive 4s LEDs up to 20A current / 15V
- drive 12s COBs to 5A / (what would be a reasonable voltage?)
So at minimum I need a 5A 48V PSU + conversion losses + some headroom. Say 450W total output.
If I can add only little to the cost and increase max voltage (48V COBs?) or current (10A 36V?) - that would be welcome.
Any suggestions then? 
Ebay ?
They do have a 60V 13,3A version for 59€ with free shipping
(The NVVV store which RDtech refers to)
I have the DPS5020, although I rarely use it up to 20A, at high amperage there always going to be some voltage drop in the wires and connections to the load, in those case I always use a voltmeter at the load and compensate the drop. And I’m pretty sure powerful 4 wires lab supply are ludicrously expensive.
I could never get the bluetooth or USB module to work…
The UI is quite annoying.
I salvaged a 48V6.7A meanwell PSU to power it, when I do use high amperage output it’s usually at low voltage so it’s powerful enough.
Thanks for the suggestion but it doesn’t work for me.
ebay has banned me and I have no idea why. I contacted them about them and they acted like “you know what you did wrong, we can’t tell you not to compromise our algorithms”. Freaking annoying when I actually don’t know and don’t think I’ve done anything wrong.
I created another account, it was banned within minutes.
Also…if I could get something worth recommending for significantly less than that I would be very glad…
i meant this one
https://nl.aliexpress.com/item/4000402850997.html?spm=a2g0z.12010612.8148356.9.53d864e2SBJTwW
If that is too expensive, then i have no direct alternative
For cheaper PSU there is also the second hand market, on a local second hand website I see some good prices for meanwell stuff.
Some people also put ATX PSU in series to get 24, 36V …etc. all but one must be de-grounded though.
If one has some lying arround this is an option.
Thank you for the information on the DPS 5020, I ordered it looks promising, not sure what I am going to drive it with yet. I purchased an ebay special that is supposed to output 30 volts @ 20 amps. tried this one and voltage sag was terrible more than .5 volts at 13 amps. I don’t have any recomendations for you. On another note I found a really neat calculator on line to compute voltage drop in wires. link Voltage Drop Calculator
I really like this one. It cost $300.00 us and is good quality.
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https://tekpower.us/tekpower-tp3030e-dc-adjustable-switching-power-supply-30v-30a-digital-display-with-back-light.html
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I do not use power supplies yet, but I want to do some anodizing in the future. So I have zero experience using them.
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I purchased the first one same item on ebay search for MP3020D Triple-Output 0-30V 0-20A DCPower Supply Regulated Variable LED half the price. For my purpose the voltage sag at 4.2 volts 13 amps was more than .5 volts, seems like good quality this is what I am going to now use to feed the DPS 5020 and hopefully get better regulation. The other one I also purchased a tekpower from amazon https://www.amazon.com/gp/product/B015QHVJP6/ref=ppx_yo_dt_b_asin_title_o06_s02?ie=UTF8&psc=1 I purchased the 15 volt 40 amp and it too has too much voltage sag same problem, I just returned it. but for the purposes of anodizing it should work perfect. There are reviews on amazon.
This is the one I purchased to combine with the DPS 5020.
https://www.aliexpress.com/item/32834100045.html?spm=a2g0s.9042311.0.0.376d4c4dlCmVBM
Had it 1 1/2 years now without any problems.
Do you think that it is better to feed the DPS 5020 with higher or lower voltage assuming the current output has the same capacities ? like say supplying with a 24 volt vs a 60 volt supply. and yes I know from reading the information on the DPS 5020 that you need to adjust the voltage below 60.
It will be more efficient when input and output voltage are as close as possible. More efficient means higher power handling. So go with 24v as long as you are good with 24v max.
Thanks, I missed that.
This is the kind of price that will make me procrastinate for some time and in the absence of a better alternative - buy. 
I see that there are some PSUs much cheaper than that…after a moderately quick search:
Page Not Found - Aliexpress.com 1200W 60V (fake rating, sustained load up to 80% or 960W) for about the same price as NVVV 720W (I suppose that dropping voltage does not allow increasing current).
Page Not Found - Aliexpress.com 1000W 60V (sustained about 720W) for $55
Page Not Found - Aliexpress.com 1000W 48V (sustained about 800W) for $47
Page Not Found - Aliexpress.com 600W 48V (sustained about 480W) for $28.
The last one is sufficient for my needs and the saving of $35 would be significant. But I don’t want to spend $29 on random junk and if I can’t find a PSU of at least fair quality - I’ll end up with the NVVV that you’ve shown. Thank you.
Thanks, I checked second hand - nothing interesting in here.
ATX in series - interesting to know. I did a quick search and what I found does not strike my confidence. I’d rather pay a little more and stay safe.