Lab power supply voltage fluctuation

[Sinosidual]

Good morning,

I recently got an inexpensive 10A 30V PSu to top balance Lifepo4 cylindrical cells. I was able to balance them at 3.65. However:

The display voltage fluctuates a little by .01V. This happens even if nothing is connected. For example, with nothing connected, votage may fluctuate from 3.65 to 3.66. This was confirmed with my multimeter. It really jumps around in the thousandths place!

In practice, while in CV mode, the amps will approach zero, then go up a little while there is a small voltage increase.

Is this behavior to be expected on an inexpensive unit? Should I return it?

Thank you

Link to the unit:Longwei Supply

 

[efficientPV]

Inspired by you, I bought one of these. Actually, I had no idea I had bought it till I opened up my email. Amazon sure is tricky. At 54.88 shipped with tax, what the heck. I will be doing something non conventional with it and modifying it right away.

 

[efficientPV]

I read a bunch of reviews and the most common complaint was setting the voltage. With fine and course pots this should be easy. It is a 30V supply and I tested it at 10V. You get a meter with 4 digits of noise. Anyone who can get this within 75mv of 10V is a better man than I. This thing jumps around like it had dirty pots. Sometimes it is stable and other times it will jump around more than 300mv. I looked at a couple open box videos and that is all they did, no real testing. I'm out in the woods, but I still have a SLINGER 1 dynamic load tester. I thought there would be a little overshoot and stuff like that. Ralph Nader would call this Unstable At Any Load. I did steps at 45Hz. First photo shows the current step function in blue. The two upper dotted lines are spaced 1V apart for reference. This is the output right at the power supply terminals. The other photo is the supply going into current limit. This is at 4A, way under the 10A limit of the supply. You are not getting a digital wonder for $50. They all must be this bad. I'm just used to supplies that cost thousands.

 

[Goboatingnow]

Good morning,

I recently got an inexpensive 10A 30V PSu to top balance Lifepo4 cylindrical cells. I was able to balance them at 3.65. However:

The display voltage fluctuates a little by .01V. This happens even if nothing is connected. For example, with nothing connected, votage may fluctuate from 3.65 to 3.66. This was confirmed with my multimeter. It really jumps around in the thousandths place!

In practice, while in CV mode, the amps will approach zero, then go up a little while there is a small voltage increase.

Is this behavior to be expected on an inexpensive unit? Should I return it?

Thank you

Link to the unit:Longwei Supply

Expecting a cheap power to hold 10 mV is fantasy. Check the voltage accuracy specs. It’s probably doing well to hold 100 mV

 

[efficientPV]

I sent mine back weeks ago and still haven't received credit. On further testing the fine voltage pot was erratic. These are the smallest pots I've ever seen, bound to wear out pretty fast. I'll just bring a spare Xantrex supply when I come back next year. I did like the size since I have limited bench space.