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Comment by minimaxir | Hacker News Reader

I recommend reading the support document because it is weird: https://support.apple.com/en-us/HT212174

- 15W charging when plugged into the battery (effectively serving as a MagSafe charger), but 5W when not (effectively the same as a normal 3rd-party battery)

- It may only charge to 90% (with the workaround being to put the iPhone into Low Power mode?)

- If plugged into the phone, it can charge the battery (is this the first use of "reverse charging" for the iPhone?)

It also requires iOS 14.7 which isn't out yet; the RC was released today so will likely be out next week.

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To clarify the first bullet point:

When the battery pack is plugged into an outlet, it will function more or less as a standard 15W wireless charger. When unplugged from the wall and drawing from it's own energy, it will only provide 5W of power.

So it has a <4000mAh battery? Those are some expensive magnets.

It's got a 1460 mAh 2S/7.4V battery (so ~2920 mAh in the typical 1S 3.7V form factor). And it connects via inductive coupling, which is inefficient, so you won't get all of that charge into the phone.

There are some sensible justifications to those metrics for battery health and charge efficiency. Stopping charging at 90%, limiting battery-based wireless power transfer to 5W instead of 15W, limiting charge levels when the devices get warm, charge management software to protect battery health when plugged in for long periods of time, charging more slowly when you don't need a fast charge, and charging the iPhone before the battery pack are all features with good technical reasons for doing them instead of technical limitations.

The naive approach of always providing 4.2V at as much current as the cell can take is bad for batteries. Apple has the required vertical integration and ecosystem controls to do some of these things that may be confusing.

I'm not disagreeing that it's not an order of magnitude more expensive than a comparable USB battery pack with larger specs.

>The naive approach of always providing 4.2V at as much current as the cell can take is bad for batteries.

More on-point with what I think you meant, cellphone fast chargers are usually putting 1C into cells below 75% when thermal conditions are met, which many consider to be stressful to li-ion chemistry. I do think this is ignoring that 1. Better charge standards like VOOC have higher efficiency and so lower thermal load, and 2. cell chemistries have improved iteratively to reduce internal resistance, again reducing heat.

Where manufacturers differ is how they deliver and convert that voltage inside the phone/device. Some of the designs (qualcomm quickcharge) dump a lot of heat stepping down a higher voltage while the earlier mentioned VOOC tries to match everything inside to meet a desired rate of charge.

Temperature is the big enemy followed by dwell time in the saturation zone. (over 80% state of charge, getting worse over 90%).

You jest, but I believe radial magnets genuinely are costly to make due to their complex process requirements. Granted, that raises the question of whether this is a product that makes any sense at all, but I suppose we'll have to see what the market says there.

I bought a magsafe radial magnet car mount on AMZN for $15

Same and it comes with charger, albeit 7W only. It’s weird almost 1 year later there isn’t actual magsafe 15W car mount.

Or maybe they're marking this thing up more than usual for some reason.

I genuinely don't know - the only magnetic charging I have on my 1st gen SE is through a dinky little adapter that plugs into the Lightning port, and since those adapters also come in USB-C and mini-B I can't imagine Apple ever getting close to the kind of interoperability they provide. I'm sure I'll have an iPhone that can do inductive charging at some point, but God alone knows why I'd ever bother using it.

Samsung gave me a wireless-charging 10,000mAh battery pack for free a few years back. Expensive magnets indeed.

> is this the first use of "reverse charging"?

It's not, the Pencil does it, too.

Various other accessories are also bus-powered.

First use of Reverse Wireless charging on an iPhone. Also, the iPad charging is one way.

Ah, I misread. From the context on the help article it's clear. I thought it referred to connecting phone and battery pack with Lightning.

Just as it should be, why would a tablet with it's huge battery charge something else? That's the job of the small phone!

But seriously, someone fucked up with the circuit design here.

The iPad Pro will charge a phone plugged into it via a USB-C to lightning cable.

iPad doesn't have any induction coils to support reverse wireless charging, but you can use it as a USB-C phone battery

Edited to clarify for the iPhone (since the Pencil is a fair counterexample for iPad)

You can also charge the pencil from an iPhone. It's just another Lightning device.

The second generation Pencil is inductive only. https://support.apple.com/en-us/HT211019

I prefer to charge my pencil via my lightning earpods.

Wondering whether iOS 14.7 also unlocks reverse Qi for other devices, e.g. AirPods. People previously assumed that there was a piece of circuitry missing for reverse charging, but this product disproves that.

Can't wait for them to do the Apple Watch with reverse charging. So annoying to have to take the non-standard charger when travelling.

But wait, why would I plug in a cable to the battery instead of directly to the phone to achieve faster phone charging? I suppose if I only had a 5 watt charger on hand? But if that is the case, why does it not charge at 15 watts when not plugged in?

You could charge the battery pack and the phone at the same time. Saves you a cable/brick when you need to charge both.

That makes sense. Feels like a stretch to advertise it as a feature. I would think the use case for this would be to charge up battery and have it in your backpack to slap on when you need it. It is nice you can charge both at once. I suppose that it can charge the iPhone up to 15 watts only if the brick it is attached to is of a sufficiently high wattage.

I think they are stretching to include that as a feature bullet point.

Overall, I actually like the product quite a bit. Not sure how justifiable the price is when The competition sells a very similar product for less than half the price, but it is nicely designed and would be a convenient piece item to have in a bag.

> But if that is the case, why does it not charge at 15 watts when not plugged in?

Presumably because of the power draw on the battery, which doesn’t matter if it’s plugged in.

You could use the battery as a charge pad. Could be handy while travelling.

> If plugged into the phone, it can charge the battery (is this the first use of "reverse charging" for the iPhone?)

If so, I want to wirelessly charge the iPhone while the iPhone charges the battery pack!

Someone will beat me to it and make a YouTube video about perpetual motion/charging

It can only do 5W charging from the battery pack, but the charging coils can passthrough line power up to 15W.

Charging the battery pack and also the device connected via MagSafe simultaneously is stated to require a USB-C power supply greater than 20W.

What might happen if both the phone and the battery are plugged into power?

The power draw from each to the other reaches equilibrium and neither charge. They just trade electrons back and forth forever.

Maxwell's tennis match.

> - If plugged into the phone, it can charge the battery (is this the first use of "reverse charging"?)

Now that's cool. It's certainly the first wireless reverse-charging that I've heard of.

This has been a feature on at least higher end Samsung Galaxy devices for some time now. There it is less restricted, and you can basically use your phone as a standard Qi wireless charging pad.

Yup, I've noticed my headphone case battery was empty and placed it on top of my phone at the gym. Sometimes it's enough to get juice for a 15-20 minute jog.

Confirmed; I've routinely used mine to charge my iPhone in a pinch when the only charger I've got is for my Galaxy device.

The first time I saw it mentioned was a Huawei phone in 2018. Samsung quickly followed, and there are LOTS of Android devices with it now.

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