DP832 display confusion - Page 1
Forum section: electronics / beginners

author: cyberwasp
author_rank: Contributor
timestamp: May 17, 2025, 04:01:29 pm
content: please excuse an old fart trying to understand new tech. Running a DP832a , output going to a 1.2v 1800mah battery. ""I know, lame use but trying to figure out the display."As you can see the V-out is at 1.6v and current is at 1800mah.At the top it always says CV=constant Voltage which it's been since connecting the battery which registered .016v at start. Shouldn't the PSU be on cc until it reaches 1.6vI have a $45 bench supply that does just that. TIA

author: Grandchuck
author_rank: Super Contributor
timestamp: May 17, 2025, 04:20:55 pm
content: When in current limiting, the display changes from CV to CC

author: cyberwasp
author_rank: Contributor
timestamp: May 18, 2025, 02:59:05 am
content: Right. However, I haven't seen it happen yet. On the $40 psu it starts in cc and when the voltage reaches it's peak setting it switches to CV and c drops

author: J-R
author_rank: Super Contributor
timestamp: May 18, 2025, 03:56:46 am
content: Not lame, but it's a bad idea to connect batteries to most bench power supplies because the crowbar circuit can kick in and blow up your nice instrument.On to your question: you are only pushing 0.559A but your current setpoint is 1.800A. So CV mode is to be expected because you're at 1.601V and your voltage setpoint is 1.600V.Side note: it's generally accepted to go with ~0.1C when charging a battery, which in this case would be 180mA. So 559mA is a bit much for such a small battery. The chemical reaction is going to be limited, which is why it won't pull more current.

author: Vovk_Z
author_rank: Super Contributor
timestamp: May 18, 2025, 01:17:39 pm
content: 1.2 VDC rated battery means that it is one of that chemistry which allows 0.1C charging current but no more. Some good ones can take up to 0.2-0.25C with temperature control.

author: bson
author_rank: Unknown
timestamp: May 18, 2025, 06:44:07 pm
content: You set the current limit at 1.8A. Your battery only draws 0.665A. Why would it be limiting? Set the limit to 500mA and you'll see it switch to CC mode.

author: cyberwasp
author_rank: Contributor
timestamp: May 19, 2025, 01:13:03 am
content: Quote from: J-R on May 18, 2025, 03:56:46 am@J-R. TY. gave up with the nimh. I do have a lithium 3.7v 8800mah battery and put a tp4056 between the psu and the battery. Am thinking that way the psu is only powering the 4056 and not connected to the battery. Not using the DP832A for this.

author: cyberwasp
author_rank: Contributor
timestamp: May 20, 2025, 10:51:21 pm
content: Quote from: bson on May 18, 2025, 06:44:07 pmTried your suggestion of 500ma, unfortunately no change. Set it up on channel two jst to see but got the same. So, it has to be me. back to the drawing board.

author: J-R
author_rank: Super Contributor
timestamp: May 21, 2025, 11:51:27 pm
content: Quote from: cyberwasp on May 20, 2025, 10:51:21 pmA typical battery will accept a large amount of current at the beginning of a charge, but that can drop off very quickly (even seconds). So it's likely that it won't accept 500mA any more at 1.6V since you've had it connected previously.If you want to see your PSU go to CC mode, then simply short the output. Obviously without a battery or anything else connected...Or, you can continue to lower the current limit until it goes into CC mode.Here are some more reasonable current/voltage limits for various batteries:AAA NiMH: 75mA/1.4VAA NiMH: 190mA/1.4V18650 Li-Ion: 500mA/4.2VBe aware that you can't actually charge NiMH properly with a constant current source. As it reaches full charge, the voltage will drop and current will actually increase, leading to heat generation and possible damage. So this is really only good for short experimentation or if you monitor the charging.Also, for Li-Ion, do not leave the battery continuously charging at 4.2V. Disconnect it as soon as it reaches approximately 4.2V and the current drops to perhaps 50mA.Ultimately, if you are a beginner you should probably start out with some simple circuit projects instead of playing with these batteries. Lithium Ion especially has a lot of energy and you can easily blow up your test equipment or some ciruit if you're just playing around trying to learn. This is why a lot of beginner kits use a couple alkaline or similar AA batteries. They can't output quite as high of a current if you short them out or make a mistake.