I wonder if Casio's heart rate sensing is far more power hungry than Garmin's, or is it just that Casio undersized the battery because they could make a lower b

I wonder if Casio's heart rate sensing is far more power hungry than Garmin's, or is it just that Casio undersized the battery because they could make a lower baseline power draw than Garmin manages. Garmins with MIP LCD screens are more comparable to the Casio line, and they have longer battery life than the OLED models. Many such Garmins can last for weeks with constant health tracking via wrist heart rate and accelerometer. It is mostly location tracking which increases discharge, e.g. ~5% per day health tracking and ~5% per hour GPS tracking. The heart rate sensor might just use ~1% per day for 24x7 usage.