DC Power Supply CC, CV Mode And Voltage Across Load

[suryaputhra]

Hi I got one DC power supply. I set at 24V and current limiting at 2 amp and load is 24V and current draw set 1.5 amp so power supply should work on CV mode but if I check voltage at load it is less than 24V My question is CV mode not working? Display show 24V but voltage across load is less than 24V so what is the meaning of CV mode.  Thanks in advance.

[suryaputhra]

Someone put some light on above question.

[IanJ]

Need more info.

PSU brand/model no.....?
Need more numbers and how/where you measured your voltages, i.e. "is less than 24V" doesn't give much to go on?
What was your hook-up?, were you using suitably gauged wire?, how long.....?

Ian.

[suryaputhra]

It is Chinese cheap model.

Setup is below

Power supply

Voltage set at 24V, Current limit is set to 3Amp

No ground

DC load Chinese model

Load set at 2Amp

Voltages checked at below places

1. Across power supply output terminal when load off. Shows 24V
2. Across load when load is on shows 22.46

Thanks in advance

[IanB]

Measurement 2 should be across the power supply terminals for consistency with measurement 1. Otherwise how can you compare them?

Secondly, what current did you measure when the load is on?

Thirdly, what allowance have you made for any voltage drop in the connecting leads between supply and load?

Fourthly, what do you see if you test the power supply with a simple load like a 24 V bulb?

[suryaputhra]

Below are the products used

Power Supply

https://www.aliexpress.com/item/New-Mini-CPS-3010-30V-10A-Precision-Digital-Adjustable-DC-Power-Supply-Switchable-110V-220V-With/32812549224.html?spm=a2g0s.9042311.0.0.MrTWeR

DC load

https://www.aliexpress.com/item/EBC-A05-Electronic-Load-Battery-Tester-Battery-Testing-Power-for-Mobile-Battery-Capacity-Computer-5V-Output/32812233688.html?spm=a2g0s.9042311.0.0.MrTWeR

[suryaputhra]

@IanB, I have given product links, look into them and my set up, pls help me.

[IanB]

Product links mean nothing, I don't own the products and I am not intending to buy them. The only way you can solve this problem is to do your own measurements and consider the questions asked.

[viperidae]

It will probably be voltage drop across your wires.

[IanB]

You buy equipment like that to learn, and you learn by doing experiments. You have done some experiments, and you have some questions. Now you have to find the answers to those questions by doing more and different experiments until you can explain what you are seeing.

Also bear in mind that the products you bought will have a range of operation, performance limits, and limitations on accuracy and precision. Your experiments should also be designed to discover those limits. No piece of equipment is perfect.

And really, the only way to learn successfully is to teach yourself. The answers you find by yourself are ten times more valuable than the answers other people may give you.

[anishkgt]

My question is CV mode not working? Display show 24V but voltage across load is less than 24V so what is the meaning of CV mode.

CV mode only activates when the voltage drawn is above the set limit ? So you've set it to 24V but the load does not pull that much. As far as i understand, the load is staying within the limit of CV and CC. Try reducing the CV to 20V and the CV should "indicator" should light up if it has any.

[suryaputhra]

@IanB I could not find answers so asked experts, if no knowledge sharing no one can learn. Why do we go schools no one can learn by alone or self.

[anishkgt]

@IanB I could not find answers so asked experts, if no knowledge sharing no one can learn. Why do we go schools no one can learn by alone or self.

Your Question is clear but you've missed out on some basic measurements for example as mentioned below,

It will probably be voltage drop across your wires.

This is one such thing you need to check. Measure the wire resistance via '4 wire method'.

You buy equipment like that to learn, and you learn by doing experiments. You have done some experiments, and you have some questions. Now you have to find the answers to those questions by doing more and different experiments until you can explain what you are seeing.

Also bear in mind that the products you bought will have a range of operation, performance limits, and limitations on accuracy and precision. Your experiments should also be designed to discover those limits. No piece of equipment is perfect.

And really, the only way to learn successfully is to teach yourself. The answers you find by yourself are ten times more valuable than the answers other people may give you.

Secondly, "experts" (one such quote above) as you say can only guide you "with what you given them". Share a pic of your setup. Finaly it also depends on the equipment also.

Hope this helps.

[suryaputhra]

My question is CV mode not working? Display show 24V but voltage across load is less than 24V so what is the meaning of CV mode.

CV mode only activates when the voltage drawn is above the set limit ? So you've set it to 24V but the load does not pull that much. As far as i understand, the load is staying within the limit of CV and CC. Try reducing the CV to 20V and the CV should "indicator" should light up if it has any.

Your explanation holds good for CC not for CV. I post set up pictures.

[IanB]

Hi I got one DC power supply. I set at 24V and current limiting at 2 amp and load is 24V and current draw set 1.5 amp so power supply should work on CV mode but if I check voltage at load it is less than 24V My question is CV mode not working? Display show 24V but voltage across load is less than 24V so what is the meaning of CV mode.  Thanks in advance.

But you have tried to set the power supply at 24 V and the load at 24 V both at the same time. You cannot do that. You have two devices that both will try to regulate at 24 V. You cannot have two control loops trying to regulate to the same value. They will fight each other.

If you want the power supply to regulate in CV mode, set the power supply voltage to 24 V and turn off the current limit (set it to maximum). Now you want the load to regulate in CC mode, so set the load to a current limit of 1.5 A and turn off the voltage limit (set it to maximum). Then you at least have a chance of the setup doing what you intend.