Cheap adjustable/variable DC PSU

krby

Solar Enthusiast
If your hobbies include anything with, DC powered devices, batteries, inverters, electronics, etc. an adjustable bench top DC power supply comes in handy a lot. Off the top of my head from the last month or so:
- Configure Inverter/Charger that requires a DC source, but your battery hasn't arrived (or you don't want to move it?)
- Troubleshoot two household devices that had DC wall bricks (12V and 5V). In one case, I figured out the wall brick was the problem (easy to replace), in the other the device was.
- Small temporary power supply for an battery charger (charging LiPo batteries RC)
- As @FilterGuy pointed out, you can use the PSU itself as a CC/CV battery charger if you don't need to balance the cells!
- Testing R/C planes and equipment on the bench without needing a battery.


I chose a pretty cheap one. In this price range / power level, there are a bazillion identical looking products. Most will do constant voltage or constant current. Among folks that know better, there is a lot of debate about whether it's worth it to buy something this cheap or buy a more expensive bench top power supply. For my needs, this works perfect, I don't rely precise output, I don't run it close to the rated limits. If you have a need for a higher quality supply, you probably know what you're looking for better than I do. My point is not to get this exact one, but that this I believe an adjustable PSU is a great bench top tool and the "not dirt cheap, but still not several hundred dollars" level seems to be a good bang for the buck.

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Ample

Solar Enthusiast
A nice looking unit. Will it handle accidents and abuse? I'm wondering what happens if you set it to say 12V and then attach a load that will draw more than it's stated max of 10A. Will it limit the current? Or will it try fry out?

I have a cheap unit by DROK. 0-24V and 20A max. But when I asked this question of DROK, they said "don't do it, damage will result" (or something terse along those lines; I got the drift). I tried to ask if there was a fuse inside that I could replace or would it result in catastrophic damage but I didn't hear back.
 

gnubie

Photon Sorcerer
These bench power supplies do current limit and not die if your load tries to draw more, but beware, it's not perfect. If you sit there tapping the wires together to provoke the current limit odds on eventually the output switching transistor will fail. It's also important to understand that these power supplies aren't really current limited, they are more current regulated. If you set 500mA as the limit then short the output you pretty much always will get more than 500mA of current as the capacitors these things invariably have on the output dump all they can into your short.

Another trap for new players is that in order to improve output stability and give the appearance of actual current limiting they tend to stick 30 odd watts of power resistors across the output inside the box. Fine if you are powering something, but if you have a battery attached and you turn the supply off, that 30w of power resistors will quite happily run your battery dead, totally stuffed, flat.
 

efficientPV

Solar Addict
I have a similar design PS in the shed. Couldn't resist it at $15 shipped. Most are linear designs. If you hear a relay click wnen the voltage is turned up, it is linear. A linear design dissipates a lot of heat and shorting the output creates more heat and eventual trouble. Switching supplies can run all day shorted and create minimal heat. There are some cheap small switchers available that easily run off a PV array. Most all my supplies are XANTREX which seem to be the nicest, but are expensive. Fortunately, getting anything repaired these days in industry is impractical. I can pick up a $2,000 supply for $50 which doesn't work.

The best deal out there are used HP 460W 12V 32A server supplies that can run your 12V stuff at home. These are almost considered E-waste and are shipped to you for $8 total. 3 pounds, shipping has to cost them at least $5. And these are spotlessly clean. Guess it is cheaper than paying to have them disposed of as electronic waste. Some business model!
 

krby

Solar Enthusiast
A nice looking unit. Will it handle accidents and abuse? I'm wondering what happens if you set it to say 12V and then attach a load that will draw more than it's stated max of 10A. Will it limit the current? Or will it try fry out?

I think it's a good bang for the buck, but I'm bet it's not hard to break if you try. I did minimal research before buying this one. Mostly at the EEVBlog Forums. That convinced me that this is not a proper high end variable PSU, but also not likely to blow up in my face with normal use. At $70, for something that outputs ~300W that's about all I expect. I don't run it at it's limits often, and I don't expect the current limiting to save small electronics from a short. From what I understand if you want more safety and better regulation, you need to spend at least a couple hundred dollars.

I did a test once at 12V using an 8AWG wire shorting the output while raising the current limit from 0 up to 10. I was ready for a problem, but everything went fine. I only ran that for many 30 seconds total.
 

carlos1w

Lego Man
These PSU will limit the current so no, it will not give you 20 A if it can only give 10 A so it SHOULD be safe. In fact, if you set CV = 3.50 V and CC = 5.0 A then the output SHOULD not go over 3.50 V or over 5.0 A. Please note the SHOULD (instead of IS/CAN)... They are probably not super well built so they will likely not take abuse very well. I doubt they will last long if you are pushing the limits (drawing 10 A for 20 hours straight). Also: there are reports that the voltage may have spurious spikes so it may not regulate so well. I would be careful if you set it charging a system and you are close to the 100% charge. Monitor the voltage with a separate meter and monitor the current (the internal one is fine). If the current does not go to 0 at your desired set voltage then carefully check that you are not overcharging.
 

HRTKD

Boondocker

gnubie

Photon Sorcerer
Weight and efficiency are the main difference for what people here would be using them with pure switched designs being lighter, cooler and much much more efficient. There are a million variations on the theme but that's the main point.
 

Zil

Solar Addict
The power supply works very well. The panel meter is not the best, so I hook my multi-meter and have 0.001 volt accuracy. I bought this power supply expressly to balance 3.2 cells. As I'm building a 12 volt system, my pocket book pick the 15 volt, 20 amp unit. I based my purchase of this manufacturer based on the trusted advice of Rod Collins. I'm not sure if he is aware theses are made in China, but China has some top electronics. I put eight 100ah cells in parallel. Set the voltage to 3.31. I used my multi-meter as the panel meter is only shows tenth volt. Using the course and then fine adjustments I had little trouble setting the required voltage. Then fastened to battery. After amps dropped to under 0.2 amp, I disconnected battery and adjusted to 3.42 volts. repeat until I was at 3.58 volts. Let it sit over night and checked that all cells were same 3.56. Then reassembled battery into 2P4S and used a sump pump to drain the battery down to 3.3 volts per cell. I let the battery sit and checked that cells stayed the same voltage. Later when I assemble the BMS and stuff, I will apply discharge and recharge testing using the power supply. The power supply was used to test and figure out how some small devices worked. I bought some low and high voltage disconnects and latching relays. They are mostly well made but have very poor instructions. I am learning a second language Oriental-English.
 

Hdonly

Solar Enthusiast
Just bought this one recently ($89.00) to calibrate a charge controller I am building from some internet DIY site. Building it to play around with wind power.71ashJRiHUL._AC_SL1500_.jpg
 

Ample

Solar Enthusiast
Thanks!

It looks like the meter has a current limiting function. Is that what the left set of controls do? That is, can you set it to 5A and the power supply will limit the current to 5A?

I'm curious what happens if the load starts drawing more than what you've set it to.
 

Hdonly

Solar Enthusiast
I haven't had time to put it through the paces yet Here is a review of the same one I bought.
 
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