what's the correct order to plug in devices for charging?

[digik]

it may seems one of those "obvious but in reality not so obvious" question, but there are many different opinions (and explanations) out there: when i connect something for charging, what is the correct plug-in order? should i plug in, for example, my phone to the charger first and then plug the charger into the socket? or should i plug the charger into the socket first and then plug the phone into the charger via the cable? I've always thought that the best way was to plug the phone (or whatever) to the charger first and then the charger to the socket, so that every surge or spike will be filtered out by the charger, but then i have also read that you should plug the charger to the socket first and then the phone so that if the charger cannot filter the surge at the initial power up it will not go to the phone. Can anyone solve this dilemma? of course i know that if the charger is properly designed it souldn't matter, but...

[Xena E]

IME.

I did used to plug in the device to the charger first, then switch on the charger, (or as you put it, plug it in), however on one occasion I did that, the charger I was using, did go Bang!

The device wasn't affected, but since then, correct or not, I've always switched on the charger, then plugged in the device.

YMMV.

This isn't a recommended procedure for charging high current / high energy devices.

Regards,
X.

[Rick Law]

Personally, I would always power up the charger first before I connect the device I wanted to charge.

As Xena pointed out, if the charger is ON first, you have a chance of seeing if the charger is working right without risking the device you intend to charge.

Besides a failed charger, some chargers (the IC's inside) may need time to power up.  Until they do, it may have a quick voltage spike until the regulator get fully power up and takes control of the output voltage. I have an example of that: the B3603 is a digitally controlled CC/CV buck converter.  I use that as my bench-supply and also serve as my 5V feed to my USB phone charge cable.  Cheap and with some problems, but it does an adequate job in holding CC and CV.  A problem the B3603 has is one should expect a very brief voltage spike at power on until the B3603 completes it power up.  So I prefer to wait till a power supply is fully powered-up before I connect anything to it.

[golden_labels]

For the past 25+ years it was being explained to me by multiple people, how important it is to use the correct order. How disasterous not following the right procedure may be. What important this and that is. After 25 years my conclusion is: doesn’t matter. Both sides produce arguments which are as equally strong, as they are equally hypothetical, anecdotal, or refer to very rare occurances.

Any reasonable consumer device on the market nowadays⁽¹⁾ must survive being exposed to people, who don’t put USB plug into mains socket only because it doesn’t fit. Safety of either the charger or the charged device can’t be compromised just because the order is not right. There may be some very poor designs, as BigClive continously shows us. But even they can’t survive on the market, if the failure frequency is too high. Their misbehavior is not consistent either,  so it seems that can’t play a role in chosing the order in which we connect things.

Disclaimer: my argument here is in the first paragraph, not in the second. Being a consumer device isn’t by itself a valid argument.

⁽¹⁾ Decades ago there were chargers, that could get damaged without load, or which would send a fatal transient downstream during boot phase. But I’m talking about the 2020s above.

[digik]

what about voltage transients when plugging the cable into the charger? not speaking about the fact that when you insert a powered cable to the usb device the contact is very intermittent in the first couple of seconds, because of the insertion process.

[tooki]

Something to consider is that if the load has big ceramic input capacitors, this can result in a big inductive spike when hot-plugging the DC side. This can be big enough to kill circuits. See: https://www.analog.com/media/en/technical-documentation/application-notes/an88f.pdf (and if you do a forum search for “an88f.pdf”, you’ll find tons of threads where this phenomenon is suspected of being the culprit.)

Of course, a properly designed gadget will be just fine being hot-plugged, using either some kind of input protection, or using electrolytic input caps, or adding some series resistance, etc. But especially when designing our own boards, or using inexpensive breakout boards, it’s a common problem.

[SteveThackery]

what about voltage transients when plugging the cable into the charger? not speaking about the fact that when you insert a powered cable to the usb device the contact is very intermittent in the first couple of seconds, because of the insertion process.

You can spend all day coming up with "what abouts" and "in theorys", but the answer is the same: in the actual real world it doesn't matter in the slightest. So, forget about it and move on.

[digik]

I have a printer that i use rarely, so i leave it unplugged and disconnected from the PC. I plug it only when i need, and when I do the PC freezes and occasionally reboots. After the pc reboots it works perfectly. Of course it does not do it always, but I've noticed two things: 1) if i turn the pc off, plug the printer via usb and turn on the printer before turning on the pc, everything works nicely. 2) if i touch the plug of the printer after unplugging from mains i get zapped! probably because there is no discharger resistor in the filtering cap. The printer is a Canon MP280 and in this case the order matter.

[Zero999]

Regarding charging. It doesn't make any difference. The device will be designed with either scenario in mind.

In the case of your printer, it's a software issue and completely unrelated to charging. Most modern consumer printers and operating systems are designed to be hot plugged, so again it shouldn't matter. Check the drivers are up to date and failing that, shut down your computer before connecting the printer.

[thephil]

It doesn't matter as long as you make sure to plug in the phone or charger at odd seconds, only.

[BeBuLamar]

I always plug he charger into the outlet first before plugging the charger to the phone. While the phone may have circuit to prevent it but I think it's possible that the phone battery can be discharged when plugged in to a powerless charger.