DC Power Supply CC, CV Mode And Voltage Across Load - Page 1
Forum section: electronics / projects

author: suryaputhra
author_rank: Regular Contributor
timestamp: November 18, 2017, 02:18:53 pm
content: 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.

author: suryaputhra
author_rank: Regular Contributor
timestamp: November 18, 2017, 04:14:24 pm
content: Someone put some light on above question.

author: IanJ
author_rank: Unknown
timestamp: November 18, 2017, 04:47:09 pm
content: 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.

author: suryaputhra
author_rank: Regular Contributor
timestamp: November 18, 2017, 05:03:36 pm
content: It is Chinese cheap model.Setup is belowPower supplyVoltage set at 24V, Current limit is set to 3AmpNo groundDC load Chinese modelLoad set at 2AmpVoltages checked at below places1. Across power supply output terminal when load off. Shows 24V2. Across load when load is on shows 22.46Thanks in advance

author: IanB
author_rank: Super Contributor
timestamp: November 18, 2017, 05:17:51 pm
content: 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?

author: suryaputhra
author_rank: Regular Contributor
timestamp: November 18, 2017, 05:58:35 pm
content: Below are the products usedPower Supplyhttps://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.MrTWeRDC loadhttps://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

author: suryaputhra
author_rank: Regular Contributor
timestamp: November 18, 2017, 06:22:44 pm
content: @IanB, I have given product links, look into them and my set up, pls help me.

author: IanB
author_rank: Super Contributor
timestamp: November 18, 2017, 06:49:22 pm
content: 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.

author: viperidae
author_rank: Frequent Contributor
timestamp: November 18, 2017, 07:39:34 pm
content: It will probably be voltage drop across your wires.

author: IanB
author_rank: Super Contributor
timestamp: November 18, 2017, 07:48:49 pm
content: 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.

author: anishkgt
author_rank: Frequent Contributor
timestamp: November 19, 2017, 04:59:31 am
content: QuoteCV 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.

author: suryaputhra
author_rank: Regular Contributor
timestamp: November 19, 2017, 05:11:57 am
content: @IanBI 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.

author: anishkgt
author_rank: Frequent Contributor
timestamp: November 19, 2017, 05:19:32 am
content: Quote from: suryaputhra on November 19, 2017, 05:11:57 amYour Question is clear but you've missed out on some basic measurements for example as mentioned below,Quote from: viperidae on November 18, 2017, 07:39:34 pmThis is one such thing you need to check. Measure the wire resistance via '4 wire method'.Quote from: IanB on November 18, 2017, 07:48:49 pmSecondly, "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.

author: suryaputhra
author_rank: Regular Contributor
timestamp: November 19, 2017, 05:51:05 am
content: Quote from: anishkgt on November 19, 2017, 04:59:31 amYour explanation holds good for CC not for CV. I post set up pictures.

author: IanB
author_rank: Super Contributor
timestamp: November 19, 2017, 06:06:17 am
content: Quote from: suryaputhra on November 18, 2017, 02:18:53 pmBut 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.