I use a Thanos Tech battery/charger to give my watch a boost during the day - when the battery is really low it can struggle to charge the watch unless it is itself plugged in to micro USB, but it’s allowed me to start using SleepWach to monitor my sleep, and still use my watch throughout the day. There are a few different similar battery/charger options out there now - this was a KickStarter product for me - which naturally blew past its original shipping date.