Wikipedia:Reference desk/Archives/Computing/2019 November 1

= November 1 =

Quick charge adapter on not supported devices
The adapter which comes with my new phone has Qualcomm Quick Charge 3.0 label on it. The output reads: 5V-3A / 9V-2A / 12V-1.5A. Is it safe to use it with my old phones? For example, if I have a very dated phone which only takes 5V-0.5A, will the adapter output 12V and fry it? And what would happen if I use that adapter with devices supporting fast charging technologies from other companies: USB-PD from USB-IF, Pump Express from Mediatek, VOOC from Oppo, and SuperCharge from Huawei? -- Livy (talk) 02:43, 1 November 2019 (UTC)


 * Not only is using an adapter with too high of a voltage/amperage likely to damage the device, it may very well explode or catch fire. As for using it with a product where the voltage and amperage ratings match, it may work, but there's no guarantee. SinisterLefty (talk) 02:48, 1 November 2019 (UTC)


 * Using an adapter with a higher maximum amperage than the device is little risk, and definitely not in the way you seem to think. Assuming the correct voltage and polarity, the device will only every draw whatever current it is designed to draw. For SMPS, if there is a massive difference between the adapter's maximum rated output and what the device draws, there is a slight possibility the voltage regulation will not properly handle such a low output, but that's only if there is a massive difference like a 20A output with a 0.5A draw and even then it's not very common nowadays. For older simple adapters which are unregulated, you do need a closer match between the current draw and rated output, but these were basically dead by the time mobile phones powered from USB came around, and in any case 3A with a 0.5A draw will likely still mean an acceptable voltage. Nil Einne (talk) 08:06, 1 November 2019 (UTC)


 * Assuming that neither the phone or the adapter are shoddily designed, it should be safe. Quick Charge, as with most similar standards which allow higher voltage over USB, is designed so the device and power adapter need to successfully communicate for the adapter to output a higher voltage. That's one of the key points of the standard. Theoretically with so many different standards it's possible one may conflict, but it's not the case for any of the major standards. As for the second question, if the device doesn't also support any of those and nor does the adapter, then it will charge at 5V with some current. To start with VOOC and SuperCharge are not higher voltage standards, so those devices will only ever charge at 5V. Theoretically they should be able to charge at 3A but it really depends on whether the device and adapter recognise any of the charger's signalling methods. It could be down as low as 0.5A. More likely it will be something higher, but probably not 3A. Quick Charge 4 includes compatibility with USB-PD but not Quick Charge 3, so most likely the device won't be able to recognise communicate higher voltage (assuming the device even uses that). For the current, it's likely to be similar to VOOC and SuperCharge. Pump Express no idea, but I expect the situation to be similar to USB-PD. Nil Einne (talk) 08:06, 1 November 2019 (UTC)
 * I should perhaps mention that when I say "most likely", while I'm in part speculating, it's not simply because I don't know but because the adapter or power bank and device may have some support for other standards that isn't well documented so it can come down to each specific device. Most devices should also try and detect if they appear to be pulling too much power from the adapter by the voltage drop and adjust accordingly. Then the connector (on all ends) [//goughlui.com/2017/11/20/usb-connector-resistance-another-reason-for-slow-phone-tablet-charging/] and cable [//goughlui.com/2014/10/01/usb-cable-resistance-why-your-phonetablet-might-be-charging-slow/] may come into play. VOOC for some reason requires a special cable. (Which AFAIK shouldn't be any risk for other devices.) SuperCharge only does to the extent that not all cables can handle 5A. USB-C, well I'll mention briefly later.  I generally check my phone with 3C Battery Monitor if I want to see how fast it is charging on any particularly combination. My current phone is a Huawei P30 non-Pro and it seems to charge ~2A (at the battery) with a number of options however although I thought some of these only support the iOS standard (anything which advertises 2.4A maximum probably at least part supports that), it doesn't seem to do so with my car charger even though I believe it also supports the iOS standard. (I think most general purpose USB power devices do.) I can often make predicts based on knowledge of the charging device but it's difficult.  I've remarked before about USB-C, and while it is IMO the future for good reason it can introduce it's own issues. Notably while technically reversibly I do have one cable which is able to SuperCharge when plugged in on direction but not the other. I've also heard of other oddities unrelated to charging with reversibility. More relevant to the question and something I neglected to mention before, it's well known, starting mostly from Benson Leung's work, that USB-A to USB-C are particularly susceptible to problems since manufacturers use the wrong pull-up resistor. As I think I said in my previous post on USB-C, I'm fairly sure some manufacturers do this intentionally since the end-user is happier if their cable seems to result in charging at up to 1.5A (or even 3A) instead of 500mA from post power output devices. No matter if this could be dangerous or damage the output device in some cases.  That's also why I mentioned shoddily designed. I'm fairly sure some phones don't bother to do anything to ascertain that they are able to pull more than 500 mA. (Especially if they're only drawing 1A or something like that.) They just do it, some may not even try to detect possible problems by voltage drop. And some chargers are so poorly designed they can barely even handle 500mA and are not particularly safe whatever you're drawing. I suspect some even do something which may lead a device into thinking it can draw more than 500 mA even though the charger isn't designed for it. For reputable brands, this isn't likely but especially since I believe you live in Vietnam where unfortunately it's likely shoddy stuff is sold more readily, you probably should take some care.  The summary, if it's a reputable phone, output device and cable, it will almost definitely be safe. But predicting precisely how fast the phone will charge is difficult without know the specifics of the devices involved.  Nil Einne (talk) 10:56, 8 November 2019 (UTC)