I've been through countless Fitbit devices by now and know that their batteries really only last about 2 years and a few months (actually the same for many wearables and if you get to 3 years you are lucky) so here my wife's Fitbit Alta HR battery has packed up after a lengthy 2 years and 8 months (a record for us actually).
I find a replacement battery on AliExpress (seems Amazon has none or did Fitbit complain about them?) and with shipping it will cost me $10.20. It seems a bit wasteful to keep dumping expensive electronics when all that is needed is a new cheap battery (and of course a heat gun for the glue, and an iFixit kit which I have thanks to the Google Nexus 6P phone battery).
I look then at $1,000 phones that live or die by a battery dying... As consumers, we need to start regaining the right to repair and replace batteries. And then I think of disposal cartridge razor blades, electric toothbrush heads, etc and the common denominator for consumers is that they cost on average ten times more than the older devices they replaced... yet we're caught up in that marketing/consumer circle of disposal.