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Help in setting up multiple Opus BT-C3100 powered by a computer power supply
#1
Hi all,

I have been creating my own charging station using a mix of Opus BT-C3100, pictures below.

I have 4 Opus and 1 Liitokala, all needing 12V, 2A - 3A. I want to power them using a computer PSU.

Since I am not using the supplied adapters I cut the individual power supplies, connected all the positives and then all the negatives together. I soldered them to a switch (rated for 240 or 120V, since I couldn't find for 12V).

I am getting strange results with my setup. The Opus are causing a short when plugged in and they trip the power supply. When I measure connectivity between the -ve and +ve going to the Opus, I get a closed circuit for an initial ~5seconds which then clears. When I plug them in, they computer PSU just trips.

When I connect only 1, it works fine and if I plug in the other 3 without (using the jack at the top of the OPus), they are all register fine and they can be used. However, when I switch off using my switch, the PSU trips again.

Have anyone experienced this issue?

The TP4056 are working fine with no issues.

Any help will be appreciated


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#2
I haven't experienced this but sounds like the switch has a short in it when switched off. if the power supply has a switch use that. or install a switch on the ac cord. The switch is designed for ac my guess is that it arcs when switched off and the arc trips the power supply.
later floyd
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#3
(07-30-2020, 01:45 PM)floydR Wrote: I haven't experienced this but sounds like the switch has a short in it when switched off. if the power supply has a switch use that. or install a switch on the ac cord. The switch is designed for ac my guess is that it arcs when switched off and the arc trips the power supply.
later floyd

Thanks floydR. You were spot on. The switch was the problem. The PSU doesn't have a switch, so I connected directly. I will look for a DC switch.
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#4
Likely you are experiencing "nuisance tripping" due to high inrush current as the charger's caps charge up when you plug it into the PC power supply. To work around that don't hot-plug the chargers. Instead, switch them on/off using the switch on the PC power supply.

Just how sensitive an SMPS is to such tripping depends on its design, e.g. I recall many such complaints about the Dell DA2 12V/16A brick which many hobbyists sought to repurpose. But its smaller brother, the 150W DA1 brick, doesn't have that problem (about $10 on eBay), i.e. you can hot-plug devices into it as you like.

To add to the above,  PC power supplies aren't typically designed to expect such high-current hot-plugging. Rather, devices that are hot-plugged into a PC are designed using (inrush) current-limiting plugs to avoid such, e.g. an (e)SATA plug mates first via longer current-limited pins that limit the precharge current. The same idea is used in various "anti-spark" cables used in RC hobbies. See here for further discussion.
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#5
Thanks Gauss
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#6
The Opus dont have large caps and initial current to Them is basically 0 compare to larger chargers. A computer have larger inrush then Turned in than 10 opus chargers have. Im pretty sure thats not the issue unless you have a PSU that is Brooken.

Though note that some older psus need both the 5v rail and the 12vrail loaded.
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#7
(07-30-2020, 06:51 PM)daromer Wrote: The Opus dont have large caps and initial current to Them is basically 0 compare to larger chargers [...]

"Large" is relative. Facts are better than guesses, and I know for a fact (firsthand experience) that the inrush current on the BT-C3100 is large/quick enough to trip protection on the Dell DA2 220W SMPS, and I've heard that it also trips some other PC SMPS when hot plugged (but I don't recall which ones off the top of my head - it was many years ago).
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#8
(07-30-2020, 07:47 PM)gauss163 Wrote:
(07-30-2020, 06:51 PM)daromer Wrote: The Opus dont have large caps and initial current to Them is basically 0 compare to larger chargers [...]

"Large" is relative. Facts are better than guesses, and I know for a fact (firsthand experience) that the inrush current on the BT-C3100 is large/quick enough to trip protection on the Dell DA2 220W SMPS, and I've heard that it also trips some other PC SMPS when hot plugged (but I don't recall which ones off the top of my head - it was many years ago).

I am new to this stuff about inrush current. I am using a HP PSU as in the attached image. Maybe it will help in this topic.

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#9
^^^ It's simplest to just test hot-plugging devices to your power supply. To deduce it from the specs would be difficult, you'd need to know the actual inrush current, and also how the power supply handles overcurrent (e.g. foldback, or momentary boost, hiccup, etc). 

Most PC power supplies will not have problems with small devices like a charger, but those from smaller PCs (e.g. "bricks" for SFF PCs like Dell DA2) are more likely to trip off. It is these much more compact bricks (supersize laptop power bricks) which are often preferred by hobbyists, and they are usually quite surprised to learn that some of these power supplies trip off when a device is hot-plugged into them. That's one reason why I thought it worth mention above.
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#10
The best course of action is NOT to hot plug equipment in, especially items not designed for hot plugging.
Just put the switch on the ac side ie the power cord of the ps.
https://www.youtube.com/watch?v=j7QuAuV5Xac
Build GIGANTIC Opus based charging station

Later floyd
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