Wireless Charging Bose Quietcomfort Gen 1 earbuds

So a little while ago I bought the QuietComfort buds to augment my existing QC-35-II headphones. In particular I wanted them for in the car where I often want to take off and put on sun glasses and over ear headphones get in the way of that (and are diminished in ANC performance by the opening of the ear pad).

This is them in the case which is also the charging unit.

I noted that they had wireless charging capacity and I was interested to experiment. I didn't have any other product which wireless charged (well, ok an Oral B toothbrush) and so I wanted to test this. So I bought a wireless charger and had a go.

Well I was pretty shocked when I picked them up off the charger at how warm they were. Warm is bad because it heats the lithium ion battery and that actually degrades the battery life significantly. Worse, its not yet summer and so its only going to get worse.

To be clear this did not happen when charging via the USB-C port.

So some quick googling yeilded this link which as well as confirming the problem shows again just how ignorant most people are about things technical because:

• it is not a copper plate but a copper coil (so failed school level science there)
• the heat can indeed cause battery degradation (and is why many phone chargers have temperature cut offs on charge)

So to reduce the conduction of heat directly between the charging pad surface and the bottom of the case I then fitted some small silicone feet onto the case.

To provide an air gap between the case and the wireless charger surface. This made a big difference from what it was before, but its still way too hot. At this point I decided that I needed to know how hot it was and so pulled out my thermal camera and had a look. 

So this is what we're seeing with the air gap space to reduce the heat.

so the bottom of the case has cooled from 55C to 37C between images, but this means the battery is still likely to be at least that hot if not hotter when it was charging (and in particular when it was charging before the feet). This link from Battery University shows exactly what I mean.

Lastly Bose themselves give indication that buds should not be charged if temperatures are higher than 39C

suggesting also that there is no temperature cut off in the bud for safe charging if over temperature exists.

Conclusion

It makes me wonder if this is part of why its been removed from the "feature set" of the latest model QuietComfort Buds II ...  

Either way I'm not going to be using my wireless charger any more and it underscores another reason for why I think its a dumb idea.

Lastly, if you have a wireless charger of a different make I'd be interested to know how yours goes.