3 ms·

I don't think that paper considers the issues of the batteries seriously enough. If you're going to build a cluster of old phones, I'd highly recommend disconn

I don't think that paper considers the issues of the batteries seriously enough. If you're going to build a cluster of old phones, I'd highly recommend disconnecting the batteries. A quick look at the phones in my drawer show two with swollen batteries and one with a battery that no longer holds a charge, which is the reason they all got retired. My appetite for risk doesn't include setting fire to a building to save money on data centre costs. I miss being able to change out the battery on a mobile and the push for making un-fixable phones has an obvious recycling issue.

nielsole 4y ago
My Samsung Galaxy S4 for example won't boot without a battery. Also the battery protection circuit is checked for. To get the phone to boot without battery i had to remove the cell from the battery and then connect a power supply to the leads of the protection circuitry. Not without risks either.
- BizarroLand 4y ago
  Seems like something that could be solved with a small capacitor bank. I may have to give this a try and see what I can figure out. I figure the input voltage would be somewhere around 5 volts and the expected output current would be 3.3 to 4.2 volts, but I bet a static 5 volts should be fine if the chip only checks to see if there is current.
  - jacob019 4y ago
    I've done this a few times, just an electrolytic capacitor across the battery pins often works.
milleramp 4y ago
Phones won't boot with battery disconnected, there are very high current spikes, especially while booting. Also there may be a required boot check for i2c/spi handshaking with the battery.
password4321 4y ago
Previous recommendations reducing risk of battery disasters on another "use an old phone" story: https://news.ycombinator.com/item?id=31841051#31843349 https://news.ycombinator.com/item?id=31841051#31843349 https://news.ycombinator.com/item?id=31841051#31842078 https://news.ycombinator.com/item?id=31841051#31842078

nielsole 4y ago

My Samsung Galaxy S4 for example won't boot without a battery. Also the battery protection circuit is checked for. To get the phone to boot without battery i had to remove the cell from the battery and then connect a power supply to the leads of the protection circuitry. Not without risks either.

BizarroLand 4y ago
Seems like something that could be solved with a small capacitor bank. I may have to give this a try and see what I can figure out. I figure the input voltage would be somewhere around 5 volts and the expected output current would be 3.3 to 4.2 volts, but I bet a static 5 volts should be fine if the chip only checks to see if there is current.
- jacob019 4y ago
  I've done this a few times, just an electrolytic capacitor across the battery pins often works.

milleramp 4y ago

Phones won't boot with battery disconnected, there are very high current spikes, especially while booting. Also there may be a required boot check for i2c/spi handshaking with the battery.

password4321 4y ago

Previous recommendations reducing risk of battery disasters on another "use an old phone" story: https://news.ycombinator.com/item?id=31841051#31843349 https://news.ycombinator.com/item?id=31841051#31843349 https://news.ycombinator.com/item?id=31841051#31842078 https://news.ycombinator.com/item?id=31841051#31842078