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Comment by rgbrenner | Hacker News Reader

This is pure FUD. I don't know how you think wireless charging works, but it doesn't send current directly into the battery. The charge is received by an antenna in the phone, and the same protections that protect it from overcharging when you plug it into an outlet apply to wireless charging too. You just replaced a cord with the antenna.

If you can damage the phone that way, then the phone is defective.

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That's not how standards work. If a cable or charging block is out-of-spec it can easily pose HW damage risks or fire hazards. It's impossible to consider every possible way this stuff can be broken.

Take for example https://gizmodo.com/a-google-engineer-is-publicly-shaming-cr...

OnePlus USB-C cables work fine with OnePlus devices but can damage any other USB-C device.

Another example where a USB-C cable destroyed his USB PD analyzer & his chromebook ports: https://www.amazon.com/review/R2XDBFUD9CTN2R

This was because the cable was completely miswired.

There's also numerous reports out there of how crappy charging blocks are fire hazards if driven at the full level they advertise.

https://globalnews.ca/news/3365247/electronic-charging-devic...

It's not totally unreasonable for a responsible manufacturer to either outright ban charging from unknown blocks/cables or to fallback to a trickle charge that disabled the highest-speed charging.

Since there's so many the only way to do this is to maintain a whitelist of good chargers at the expense of fast charge not working with an arbitrary number of chargers. You could think "well, just warn the user & give them a choice." However, the majority of users would just learn that most of the time it's OK & just hit "OK" blindly even when connecting to new chargers they don't know about. Also the news reporting would still be the same & wouldn't capture the nuance of using a third-party charger since news cycles are more instant & don't allow the necessary amount of time for engineers to receive the unit & perform diagnostics to figure out what happened.

> Another example where a USB-C cable destroyed his USB PD analyzer & his chromebook ports

That sounds to me more like a shitty design on both of those.

Short of sending hundreds of volts and causing arcing, this should be preventable, should it not?

Non-shitty devices will behave well, but shitty ones won't. That's the problem.

That cable supplied voltage on the ground line. Quite some WTF factor on that, but also difficult to protect against.

You can protect against reverse voltage, ie, voltage from the ground line.

A simple diode is the easiest way, using various power MOSFETs can reduce the voltage drop induced and you can even build a circuit that allows charging the battery and supplying power on the same connectors while also protecting against reverse voltage.

It's neither hard nor expensive.

TIL.

Are you saying that it's possible to protect against all kinds of shenanigans on the ground line even if the device has no other ground, or only against negative voltage?

There is only reverse voltage and over voltage.

Ground is basically your reference, if your ground has potential above your voltage input, you're in reverse voltage, if your ground is too far below your voltage input, then you're in over voltage.

Both can be detected and prevented from causing damage via various means on both sides of the usb plug.

Overvoltage can usually be solved by having a Zener diode within acceptable overvoltage short the thing to ground and blow out a fuse, this will cut the circuit and prevent further damage.

I recommend this video from GreatScott: https://www.youtube.com/watch?v=7Tk5ghH_U2s

>https://gizmodo.com/a-google-engineer-is-publicly-shaming-cr...

That's exactly what I thought of when reading the GP. There is some absolute garbage out there being sold.

There are also manufacturers using the existence of such garbage as a scapegoat.

For instance, the fitbit ionic battery plague is caused by shorted MLCCs -- but they still try to blame it on 3rd party chargers every time they get an RMA.

Some devices will break when you draw advertised levels of power. That's just a fact of life, and isn't something you should try to fix with DRM. It's not a very common thing.

It also doesn't damage the device itself.

The backwards cable is worth noting but not relevant to a system that's fundamentally AC.

Outside of some kind of massive EMP, nothing a wireless charger does should be able to hurt your battery.

That’s why circuit designers almost always create charging and power circuits with over voltage and current protections into fragile electronics. Certainly on a system as fragile and complex as a cell phone. This isn’t an excuse, this is bucking trends of circuit design that has existed for decades. And it’s even easier to prevent in wireless transmissions than physical ones because wireless requires careful tuning of resonance to work efficiently. The circuit to prevent this would be simpler than this handshaking one to detect “ok” chargers.

If I were being generous, I'd say that there are parts of the charging process (variations in charge, temperature, etc) that the hardware can't monitor, but have to be kept in certain ranges to maintain good lifetime/safety for the battery. So, instead of adding the sensors, they're restricting the charging devices. I can imagine that wireless charging is a bit complicated (see apple's problems) and it's easy for other vendors to get it quite wrong.

If that were the case, I think that they should include the stand with the phone.

Otherwise I think it's a bitter-tasting money grab.

>Otherwise I think it's a bitter-tasting money grab.

It's engineering laziness. Designing a phone robust against bad chargers is harder than designing a phone to work with one charger and putting DRM on it. It's the kind of thing markets can't do very much to solve which requires regulation, unfortunately, because there are too many bad actors.

i get that this is theoretically inconvenient for you, but how big of a problem is this really? afaik, most people don't wirelessly charge their phones, even if they have capable devices, and the pixel line tends to be pretty low volume to begin with.

given the small number of people that actually care and the possibly large cost of supporting full speed charging on a wider range of chargers, I'm not sure this is a problem at all, let alone one that merits new regulation.

If you assume faulty charger, you have to figure out a way of dropping at least 5 extra watts of heat somewhere in your phone. That seems practically impossible without significantly compromising on mechanical properties of your device.

All Qi chargers already have a temperature sensor in them and any modern phone has many temperature sensors (MEMS sensors, SMPS, lipo battery charger). The Qi receiver already communicates back to the transmitter and can tell it to increase or decrease power. Having the Pixel 3 decrease charging rate if it noticed heating up would be trivial.

You're forgetting the problem of the charging stand being implemented incorrectly & catching fire. Phone sensors won't help you there & while you may think all Qi chargers would have a temperature sensor in them, the fact that something simpler like knock-off USB charging blocks cause fire hazards leads me to not be so bullish on the Qi front.

And hey, look.

https://www.youtube.com/watch?v=CEGlmQS692w https://www.youtube.com/watch?v=IxstYrJQkk8

I'm sure you can find more examples. Just because we'd like the world to work a certain way doesn't mean it actually does in practice & the job of engineers sometimes is to deal with the reality of the world.

The issues you raise aren't solved by limiting transmit power - they are only solved by actually using Qi standard chargers. If you are using a faulty transmitter it can catch fire at 5W or 10W.

The Qi standard as of 1.1 has the receiver communicate back to the transmitter the amount of power it has received. The transmitter then calculates transmit efficiency based on the amount of power it is outputting. If the efficiency is too low the transmitter will fault with the assumption that it could be heating up a foreign object.

From the Qi Wikipedia article:

> Rather than down-regulate the charging voltage in the device, Qi chargers meeting the A2 reference use a PID (proportional-integral-derivative) controller to modulate the delivered power according to the primary cell voltage.

So... a defective charger could plausibly damage the phone unless the phone contained a suitable protection circuit. Such a circuit could be quite simple - a transistor set up such that switching it would take the resonant receiver out of resonance would do the trick. The designer would need a bit of care to ensure that switching the transistor under wouldn’t fry it.

But IMO this design is a bit nutty. Phones already have voltage converters. Why not just use them?

When the flea market charging pad that the Google phone is laying on goes up in flames, Jenny Cheapskate isn't going to know if it was the pad that burned down her home, or the phone.

Your logic allows me to lock up all hardware in an Applesqe way and get praised for my altruism as I pocket hundreds of millions in extra peripheral sales.

The world has gotten this far with standards that allow equipment from different manufacturers to function together in a system. What a shame if marketing people and greed destroys that ecosystem.

Hundreds of millions from the sale of Pixel 3 Qi chargers seems wildly optimistic.

...now. How about in 5 years? Will we still be plugging the wires to our portable devices?

yes.

I certainly hope so.

if you want fast charging, yes.

That shit could still happen. They aren't preventing the chargers from working, just not working as well.

Actually in some cases you can. E.g. Gear S3 uses proprietary charger that is rated at 0.7A, 5V at the input. And several people reported watch raising overheat alarm when charging with select 3rd party chargers (not all). Apparently Samsung made it so the watch charges will really weak power, slowly and using powerful 3rd party chargers may push it out of the rated parameters. No permanent damage reported afaik.

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