Solving a wireless charging mystery

Article By : Brian Dipert

How many devices have been unnecessarily thrown away based on this understandable but incorrect diagnosis of premature demise?

I like my first-generation Google Pixel smartphones so much that, for Christmas, I bought my wife one, too, to replace her misbehaving iPhone 6. Hers is the larger-screen Pixel XL model and, for reasons that to this day escape me, I had it (wrongly) stuck in my head that the larger form factor enabled manufacturer HTC to squeeze Qi wireless charging support into it, akin to that included in Samsung’s last few generations of Galaxy handsets or Apple’s iPhone 8/8Plus and X. And unfortunately, I over-relied on my faulty recollection, passing this flawed nugget of information on to my wife without fact-checking it first. She was, of course, disappointed when she discovered the error of my ways; her sister is a longstanding Samsung Galaxy owner and had long extolled the wonders of wireless charging.

No worries; a few extra bucks (mostly) fixed the situation. My wife normally keeps a thin case on her phones anyway, to protect their backsides; a svelte and inexpensive wireless charging accessory slipped in-between the phone and case added Qi support to the case-clad Pixel XL at the tradeoff of monopolizing the phone’s USB-C (formally known as USB Type-C) port. This Seneo wireless charging stand works well, too; she has several of them scattered around the house for battery top-offs in-between calls. Although the engineer in me knows that wireless charging is less efficient (i.e. slower) than the conventional cable-tethered alternative, I can’t argue with the convenience. And given that full recharges take place overnight while we’re sleeping, the charging rate is (within reason, of course) a don’t-care, anyway.

For heavy phone usage days, we also got her a Mophie Juice Pack battery-inclusive case, which also has built-in Qi charging support along with a conventional USB-C port. The feature set sounds good, at least in theory, and truth be told it’s pretty good in reality, too … with one exception, which prompted this particular post. She recently went on a several-day business trip and took the Mophie-augmented Pixel XL with her, along with one of the Seneo charging stands. She did not also bring a conventional USB-C charging cable with her, because … why bother, after all?

When she got home, she reported that the Mophie had quit working and that her phone’s own battery was nearly dead. Eventually, I sorted out what had transpired, and why. She’d had a busy last day of work, which had completely drained the Mophie’s supplemental battery as well as depleting the phone’s own. When she put the phone on the charger at the end of the day, the Seneo’s front-panel LED changed from blue to green, indicating that the Mophie’s presence was recognized … but charging didn’t actually take place in this particular case. And without the Mophie’s battery being replenished, the phone’s own battery wasn’t getting refilled, either.

What happened here? This is where the engineer in me came to the fore. The electron transfer from the Mophie to the phone is unidirectional; the battery case can power the phone, but not visa versa. This means that when the Mophie is connected to the charger wirelessly, its battery serves two important roles; powering the phone, and powering itself, specifically its own Qi receiver and other recharging hardware. But if the Mophie battery is completely drained, it can’t power itself, therefore can’t wirelessly recharge itself.

The “fix” for this scenario, of course, is to instead recharge the Mophie via USB-C, thereby supplying it with external wire-delivered power … which is what I did. It’s once again working fine … as long as we don’t let its battery completely drain again, that is. Suffice it to say that going forward, my wife will make room in her travel bag for a backup USB-C cable and conventional charger. And in case you’re wondering, there’s no mention of this particular quirk in the user manual, at least that I can see.

Situations like this admittedly drive me nuts; I wonder, for example, how many Mophie Juice Packs have been unnecessarily thrown away or returned for refund based on an understandable but incorrect diagnosis of premature demise. Or, at minimum, I wonder how much unnecessary consumer time and angst has been consumed on the phone, in 1-1 chat or in email back-and-forth with Mophie’s customer support … time which is an unnecessary expense to the company, too.

A bit more effort spent in upfront field testing prior to production would have, I suspect, uncovered the issue, enabling Mophie to at least properly document it, if not add hardware support to the juice pack to preclude full battery drain prior to wireless recharge. Your thoughts, folks, either on this particular situation or analogous ones you’ve experienced either as a consumer or with your own company’s products? Sound off in the comments.

Brian Dipert is Editor-in-Chief of the Embedded Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

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