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I'm talking about Banksy's "Girl with balloon" painting that shredded itself at auction.
I think the general consensus is that he didn't, and that it was set up before the auction (or a couple years ago, not 12 years). But lets say he did, how could he have made it keep its power for that long? What sorts of RF receivers run on such low power? What batteries can withstand a 12 year low-but-constant-load life?
A relatively large lithium primary cell would be my choice. They are specified for something like 10 or 20 year life running water meters, including periodic radio communication. And maybe a second cell to run the motor so it stays relatively fresh.
The Israeli company Tadiran makes such products.
As long as the temperature does not get too high the shelf-ish life of such Lithium cells is in the decades (they claim 40 year operating life). You can bet that an expensive piece of art will be kept in carefully controlled temperature and humidity conditions.
Given that power source, power management would be important but not crazy critical. You would want to keep the average draw in the << 100uA range most likely. Doing the sums, their 19AH TL-4930 works out to 54uA (average) for 40 years. So even if it turned on a receiver once per 10 minutes for a second it could draw tens of mA, provided the sleep mode power was inconsequential.
The most likely answer is that he didn't. While that was the claim, it is much more likely that he swapped out the frame soon before the painting went up for auction. Dave Jones from the EEVblog did a video on this:
https://www.youtube.com/watch?v=SdKdQWhlNTY
UPDATE Here's a follow-up video from the EEVblog:
Why would it be a low-but-constant-load life?
Assuming the auction takes hours, it would be enough to awake the RF receiver once every hour for a few ms to check for an RF signal.
The transmitter would either transmit the RF signal: - For a complete hour, knowing the RF receiver will be awake at least once - Know in what time period (like every whole hour) the receiver will be awake and send it within that time.
In both ways, the transmitter can continuously send the message, only the receiver needs to receive it only once.
** Update after James Trotter's remark **
New algorithm:
Passive RFID tags run on zero batteries. The RF signal itself carries sufficient energy to power the RFID tag.
Now we know that a big battery had to be present for the shredder, but we can use a small wakeup circuit to keep that battery entirely disconnected for years, and only connect it when the passive radio receiver is energized.
Primary cells, a arming switch, and non-rf method of control, like IR, as there was a plant in the audience. They could easily sit for years and still be good. It was discreetly armed right before auction.
But as Banksy's instagram video showed, it didn't work right. In rehearsals it shredded it completely. This is likely due to how long the batteries sat in the frame. Even top quality Alkaline primary cells would show signs of aging 10 years later, enough for large motors to only work half of their intended job.
