It would run an alarm clock /time lock set up to send a signal or switch on a servo operated lock after 10 years. I don't know specs or power need for servo, might be separate system (and a separate question) . Focusing on the power requirements to operate a raspberry pi zero w continously for 10 years in an enclosed system with no possibility to swap or recharge the battery for the given period. Edit : the initial system would low power idle until given time and date without any led or displayed output. It would then send a signal or current to servo lock mechanism to unlock and power down or idle when task is completed.
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If you have an online power requirements calculator please link in comments.– marc-andre benoitJun 18, 2019 at 16:13
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I'm just researching for now. It's not an ongoing project.– marc-andre benoitJun 18, 2019 at 16:16
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It must depend what else you're going to have it do. If nothing, then it's not clear why you want the Pi in there at all. You could make a timed lock without a controller.– BrickJun 18, 2019 at 16:26
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1Is there a reason it needs to run continuously as opposed to sending it into low power sleep and waking it up once a second to check the time? Another finesse would be to have it wake up at much longer intervals until the day or hour of the trigger and then once a second until "The Moment". I'd also recommend lithium batteries due to their long shelf life.– BobTJun 18, 2019 at 16:28
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2If your main concern is power, then a Raspberry Pi is not the best choice. It would be better to use a microcontroller designed for low power requirements.– Glen YatesJun 18, 2019 at 17:15
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2 Answers
According to raspi.tv, the idle current is 120mA. Sizing the battery for 10 years:
That would be an enormous battery. Based on this tomsguide.com article, a Moto G7 Power has a 5 AH battery, so you'd need the equivalent of 2,104 Moto G7 Power batteries to provide that much power. That's not even accounting for any other power loss the battery may suffer, and you'd need a battery with a shelf life greater than 10 years.
In case the cell phone battery count wasn't impressive enough, based on this calculator, that'd be a 54.595kWh battery. In other words, you would need more capacity than that of the high voltage (drive) battery in a Tesla Model 3 SR according to this Wikipedia page, which references this archived Electrek article.
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Thanks for the calculations and references. It's well appreciated! Jun 18, 2019 at 18:51
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1It's much worse than that, as all batteries have some form of self-discharge, which will reduce the usable capacity. In short term applications under a month that is often negligible, but many batteries will have no usable capacity after ten years even if no current has been drawn. In some technologies (e.g. Lithium Thionyl Chloride), the battery is also degrading when no current is being drawn and needs some 'reconditioning' periodically to use the full rated capacity. Both of these effects tend to be worse as temperature increases.– rolingerJun 20, 2019 at 10:25
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Yes, that's a more detailed version of what I meant by this: "That's not even accounting for any other power loss the battery may suffer."– rpseuJun 20, 2019 at 14:24
As you only require it to do a one off tigger in 10 years I would have thought a very low power microprocessor with a deep sleep mode would be the way to go.
