Hello,
My son lost his Meta Wayfarers smart sunglasses charging case. To replace it is $100, so I thought I'd take a crack at a DIY approach. I have a USC-C to USB-C cord coming from a wall charger and going into a voltage/current tester showing about 5.2A, into a buck converter, then the buck converter's positive wire going into a IN5817 diode, then the positive terminal on the glasses, with the ground from the converter going to the ground on the glasses.

Meta made no attempt to distinguish which side was positive and which was negative, however, and the potential for confusion is compounded by the "left side" of the glasses being relative to 1. wearing them 2. looking at someone wearing them 3. if they're upside down, etc.

When I started charging them, one stem got pretty warm. Not hot, but warm. I worried I had reversed the polarity, so I double-checked some stuff online about which side was positive, and I think I might well have screwed it up.

However, when I did it the "right"(?) way, the glasses pull no current and nothing happened after ten minutes (which I figured was enough time for a totally dead (like, months dead) battery to draw enough charge to light the charging LED, for instance. The other polarity, btw, was pulling about .5A.

So, I may have screwed these up, but I'm open to any advice on how to deal with this mess going forward.

Thanks.

 

Welcome to AAC.

While is it possible you damaged the charging circuit (500mA is quite a bit of current) it is impossible to know if that is the case.

One possibility is that a poor design allowed you partially reverse charge the cell until its over discharge protection was triggered and now it is inaccessible. I have never seen the Meta glasses in person, but I think that unless a repair service is available at a reasonable cost, your only option will be to disassemble the glasses and replace or remediate the cell.

 

So, I do think it triggered discharge protection, but - looking into it - perhaps it was only until reset, for a certain amount of time, or until it sensed the authorized charger because - thankfully - it charged again and seems to be working with the actual charger. Bummer I had to order another one, but - this time - it beat risking real damage with a DIY attempt.