D Rigol DP832A Programmable Linear Dc Power Supply, - Page 1
Forum section: electronics / beginners

author: cyberwasp
author_rank: Contributor
timestamp: April 08, 2025, 03:54:02 pm
content: I read in the comments of a video of Daves that when using this power supply it was advisable to use a blocking diode as the outputs are sensitive to V inputs. Are the 15SQ045 Schottky diodes adequate for the task. TIA

author: RoGeorge
author_rank: Super Contributor
timestamp: April 08, 2025, 05:25:09 pm
content: That diode might be OK, depends what you are trying to do. No additional diode is needed to power normal circuits. A series diode is usually needed if the DP832 is used for charging (big) batteries.What exactly do you want to power with the DP832?

author: cyberwasp
author_rank: Contributor
timestamp: April 08, 2025, 10:59:40 pm
content: Mainly charge a 18650 3.7v 2200mah battery. I know it major overkill but it's how I learn. Plus I tried it with a cheap Nice 30v 10a $30 power supply that did nothing and thought the rigol would prove or disprove the nice charger. I set it at 3.5 volts at 2200ma and it didn't do anything. The Rigol is arriving tomorrow and just wanted to make sure of what the others were saying. Here's the protection I came up with if necessary.battery is 2200 not 3200, typo

author: thm_w
author_rank: Super Contributor
timestamp: April 08, 2025, 11:17:45 pm
content: Yes 15SQ045 is adequate. Diagram is good.Highly recommend that if you are doing this more than once to simply spend the $20 on a dedicated 18650 battery charger. To avoid any accidents that could cause a fire.If you set at 3.5V and the battery was 4V already then its not going to do anything. Use a multimeter to measure the battery voltage.Your power supply would be set to 4.2V or so, and current limited at 0.5 to 2A.

author: cyberwasp
author_rank: Contributor
timestamp: April 08, 2025, 11:45:27 pm
content: Thank you. I'm 69 years young and the old mind isn't what it used to be.

author: incf
author_rank: Frequent Contributor
timestamp: April 09, 2025, 02:19:50 am
content: Quote from: cyberwasp on April 08, 2025, 03:54:02 pmI have that exact supply and a DC load for simulating series 12V batteries for a 24V battery charger product.I've been running without diodes (with external source injecting a current) and the supply is undamaged. But lack of diode does tend to affect it's voltage/current regulation in a very unpredictable manner.I definitely recommend diodes - you could get away with a smaller one.

author: RoGeorge
author_rank: Super Contributor
timestamp: April 09, 2025, 07:58:03 am
content: It's good practice to use a diode even for a single Li-ion cell. In fact if you read the DP832 User Manual (please at least browse it), there is a wiring diagram with a series diode for charging batteries. That is for the case when, by accident, the battery becomes the energy source and the DP832 becomes the load. This can happen in case of a mains power surge, or at an accidental DP832 reset, or if a DP832 channel output suddenly becomes defective or 0V, etc.A dedicated Li-ion charger would be preferable. To be honest, I only use a series diode when charging bigger batteries (for example when charging 12V Pb batteries). I don't use a diode for single cell Li-ion batteries, but I NEVER let them unattended.This is my series diode(s) when charging 12V Pb batteries:I use CH1 and CH2 in parallel, each channel with its own series diode(s), to charge a battery at max 6.4A (3.2A from each DP832 channel). Those in the pic are in fact 2 paralleled Schottky double diodes (recovered from defective ATX power supplies for PCs) on a leftover radiator from a retired AMD processor.About the DP832 settings when charging Li-ion cells, read on the battery body, or search for the specs/datasheet, to know the charging current, the stop voltage and the stop current. Usually, Li-ion have printed on their body (nominal) 3.7V and the mAh. 3.7V nominal corresponds to 4.2V stop (top) charging voltage.I use to charge them at 0.2C, where C is the capacity in mAh. For example, for a 3.7V/2200mAh, I set the voltage at 4.2V and the current at 2200*0.2 = 440mA, which means a complete (slow) charging will take about 5-6 hours, but it can happen faster if the battery was only partially discharged.The battery disconnect criteria is usually when the charging current drops under 0.1C or so (becomes less than 220mA for the above example of a 2200mAh 18650).Other Li-ion models can be, for example, 3.65V or 3.8V nominal, with the (s)top charging voltage 4.1 or 4.3V, and there are now some many other types, including of much lower than the typical 4.2V, that is why it is important to read the battery specs. When overcharged above their max voltage, they can catch fire.About 18650 type, there are 2 categories, protected and unprotected/raw cells. The protected type have a small electronic board inside the battery, and a fuse. That will automatically disconnect the battery when discharging it under 2.8V or so, or when overcharging above 4.3V, but in normal charge/discharge cycles, those limits should not be reached other than by accident.Usually, DP832 can only source current, but can not sink any current. In other words, can only act as a power supply, but not as a load. So DP832 can only charge a battery, can not be (normally) used at discharging a battery (for example to discharge with the purpose of measuring the mAh).However, there is a trick to use a power supply as load, such that it is possible to measure the mAh of a battery while discharging it, like this:https://www.eevblog.com/forum/projects/cc-cv-power-supply-as-a-contolled-load-for-batteries-(i-e-rigol-dp832)/These pics are for 1.2V batteries, but it can discharge Li-ion just as well.In any case, with or without the additional series diode, DO NOT let any battery to charge unattended, particularly Li based (unprotected) cells. They can start a fire, either because of the battery, or because of hardware/software defect, or because of an external unexpected events.Congrats for your new DP832 power supply!

author: bson
author_rank: Unknown
timestamp: April 09, 2025, 11:49:17 pm
content: Definitely use a diode, like of the schottky rectifier variety.

author: Smokey
author_rank: Super Contributor
timestamp: April 11, 2025, 08:34:31 pm
content: What is the DP832 failure mode if it's outputs get a low impedance voltage applied? Under what conditions is this actually dangerous to the supply?I get that it's only a 1 quadrant supply, but I feel like I've had situations where one of the outputs is driven higher than it's setting voltage and it hasn't blown up on me. Hell, I've paralleled it's out output channels that had voltages accidently set to drastically different values and it didn't appear to care.

author: thm_w
author_rank: Super Contributor
timestamp: April 11, 2025, 09:45:23 pm
content: Quote from: Smokey on April 11, 2025, 08:34:31 pmIts not instantly going to blow up, but for a beginner its just better not to risk it.https://www.eevblog.com/forum/repair/rigol-dp712-output-shorted-fuse-i-screwed-up/

author: Smokey
author_rank: Super Contributor
timestamp: April 11, 2025, 11:13:10 pm
content: Quote from: thm_w on April 11, 2025, 09:45:23 pmOk. Check me if I'm wrong with this.See schematic from Harry_22 minus the external diode:https://www.eevblog.com/forum/repair/rigol-dp712-output-shorted-fuse-i-screwed-up/msg5471857/#msg5471857So there are two failure modes we are talking about then?1 = Reverse Polarity external source.If you hook a source voltage up to the output of the power supply backwards then the internal diode across the output rails will be forward biased and conduct.(I confirmed this is true. Reverse polarity will conduct. Bad news.)2 = Over-Voltage Crowbar Trips.If you happen to trip the over-voltage protection threshold on that channel and the output crowbar activates to discharge the output cap then it will also conduct external source current as an internal short on that channel. Unknown how long this condition exists, ie how long the crowbar is active. But I'll take your word for it that that would happen and it would be long enough to be bad.Ok, Ok. With that said both of these conditions are not limited to charging batteries and are equally likely with any external source including paralleling channels from the same power supply.https://www.globaltestsupply.com/pdfs/cache/www.globaltestsupply.com/dp832/manual/dp832-manual.pdfGiven that the manual has a section and connection diagram for parallel connections, I guess the idea would be that they hopefully used diodes and crowbar components that can handle more than the 3.2A max from it's own channels, but an external battery could be significantly more than that.Everything has a risk, and this is no different. The take away should be understanding and avoiding the risk.Don't hook up reverse external voltage sources to your supply.Don't trip the over-voltage crowbar when an external supply is connected.If you can deal with the voltage drop and power dissipation of a diode (ideal or otherwise) in the output, then go for it. Else just be careful (which is generally good advice).ps. One thing to note is that whenever there is an external source voltage correctly connected (including paralleling it's own channels both in the same polarity) there is a constant current draw on the order of about 20mA into the DP832. That always seems to be present, so that's something to be aware of.