Power Runaway

Managing energy consumption in battery-powered electronic gadgets is one of the most difficult engineering tasks. And no one has dine it 100% right. Low power consumption is only achieved through managing the device activity. A device may really be designed to and perform consuming manageable amount of energy, until once in a while it runs away and dies.

A 2018 MacBook Pro runs for 8 hours under macOS and only 90 minutes under Windows. The reason? The accelerated graphic card (the ATI Radeon GPU) is tightly managed by macOS (by switching it off and using the integrated low-performance / low-power Intel GPU). Wen booting Windows, the Apple BIOS disables the Intel GPU so Windows has nothing to switch back to and consequently draws batteries at full speed.

My Garmin Delta watch has a habit of draining its battery to death in the night when it repeatedly attempts to connect to the iPhone to sync data. I have a habit of leaving the watch on a kitchen table and taking the phone with me to the bedroom and most of the time then they are out of the Bluetooth radio range. And the Garmin keeps ferociously trying to connect depleting the battery. There clearly should be a backoff procedure. Maybe there is but has not been tested and does not work as expected. Anyway, often I find the watch dead, sometimes exactly when I need it going out on a morning trail run.

Then there is the iPhone. Which seems to be perfectly engineered to take care of all potential edge cases. And it has recently failed on me too.

iPhone is very effective (battery-wise) to play videos and I use it quite often to watch the "Watch later" downloaded YouTube videos on a plane. Last week when boarding a 2-hour London-Krakow flight the phone was 48% charged, so by my experience it would easily last until the next day, even if I played YouTube through the entire flight. But then it shut down itself after just one hour. Incredibly draining the 48% of the battery during that time. And it was very hot when I touched it.

What went wrong? I have no idea. The only thing I did differently this time was I engaged the flight mode and then disabled the eSIM data card I was using in the UK. It seems this sequence caused either the processor or the cellular modem to remain highly active, which as a consequence drained the battery.

This is why it is always prudent to have a power bank. Even a small one.

Of course a drained battery is not a catastrophic failure. We are surrounded by power sockets and chargers. Until there is a situation when the nearest source of power is a couple of days away.