> One of the more difficult features was the rechargable battery.

Flat ones do exist. I have one eink TOTP card that's no thicker than a normal credit card.

And also an airtag style tracker that's about twice as thick. Maybe it uses the same kind of battery.

bookofjoe 8 days ago | parent | next [-]

O.4mm thick rechargeable battery:

Standard credit card: 0.76mm thick

uticus 8 days ago | parent | prev [-]

seems dangerous to have terminals of battery exposed, shorting (and with rechargeable, burning) hazard

	▲	spacedcowboy 8 days ago \| parent [-]
		Some conformal coating spray would probably be all that’s needed.