On a side note, curious about the viability of this tech…
Before becoming a Bubble developer I worked in telecommunications for quite a long time, so this analysis I found seems to tie up with my understanding. I think you’d spend considerably more energy running your phone in standby, let alone running the app itself vs. whatever energy you could harness from Bluetooth to charge your phone’s battery.
Your typical Bluetooth connection is designed as a PAN, a personal area network. It’s intentionally not designed to go far. So most Bluetooth transmitters are either Class 1, at 0dBm = 1.25mW, or Class 2 at 4dBm = 2.5mW.
But that’s the power out of a Bluetooth transmitter. Your phone is receiving a signal somewhere around -40dBm, which is 10^-4 mW or 10^-7 Watts. And it must work down to at least -70dBm. That’s 10^-7mW or 10^-10 Watts.
A USB 2.0 power dongle usually runs at 7.5W. A QuickCharge 2/3 power dongle can provide 18W, and USB Power Delivery can go to 100W, though no phones are using that much power.
Let’s charge my phone on an 18W charger and assume it can actually take an 18W input and has a 95% efficient power conversion/charging circuit. My 4000mAh battery charging will store 14.4W power, and though it can’t charge that fast, let’s call that about an hour on the 18W power brick.
So what if we did charge 10^-7 Watts, assuming we could convert all of that energy into a charging voltage. Well, rather than finish charging in an hour, your phone would actually take 16,427 years to fully charge. Which of course it wouldn’t actually do, since the self-discharge rate of the battery is around 1–2%, much faster discharging than charging.
Bluetooth is only concerned with transmitting information, not power. And only over a very short distance. But even if you were charging at 2.5mW, you’d stil take about eight months to charge the phone. Even a USB data port, which is about the slowest charging you’ll ever get, is a 2.5W power supply, 1,000x more power than the power coming directly off the Bluetooth antenna in Class 2 mode.
But I wish you the very best of luck
Josh @ Support Dept
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