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What battery chemistry would be most suitable for an application where the cells are expected to sit a very long time, say 100 years, disconnected, with minimal self discharge?

Assume the storage temperature would be something on the order of outdoor extremes experienced in inhabited places on Earth, say -50°C to 50°C or so.

Assume the operating temperature range would be narrower, say 0°C to 30°C or so.

It need not be a chemistry currently available in any commercial products. Assume environmental concerns can be overcome.

Assume the current demands are relatively low, for a small electronic data processing load and that physical space can be found to make a battery of sufficient capacity.

Assume that a hard switch (not a semiconductor) will disconnect the battery from the load.

It doesn't have to be a voltaic cell necessarily, just a self-contained means to store or generate electric energy. It must not rely on external sources of energy like sun, wind, water, or physical effort (like cranking a dynamo) which might not be available when the system is finally turned on.

To clarify the intent, this would be for a "time capsule" type use where it's expected to be sealed into construction, but must be able to power up in the future with no expectation of available external power.

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    \$\begingroup\$ Wet cell chemistries stored without water and well-sealed can last a long time; the battery doesn't really start being a battery until you add water to it. I don't know about 100 years, though. \$\endgroup\$
    – Hearth
    Mar 8, 2023 at 16:33
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    \$\begingroup\$ Does it have to be a battery in traditional sense? How about solar cells, RTG/nuclear, thermal generator, hydrogen cell, watermill, or wind generator? \$\endgroup\$
    – Justme
    Mar 8, 2023 at 17:34
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    \$\begingroup\$ Does it need to be a chemical battery? Can you pack a hand or foot-powered generator with assembly instructions? Coils, magnets, and mechanical parts, stored properly, are likely to last as long as anything else you can store in there. \$\endgroup\$
    – Matt S
    Mar 8, 2023 at 18:08
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    \$\begingroup\$ Are there constraints on size? \$\endgroup\$
    – Nat
    Mar 9, 2023 at 1:54
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    \$\begingroup\$ As commented below, be careful in choosing all the components, esp. capacitors. No electrolyte-based ones, possibly no ceramic ones (moisture sensitive). Provide a thick conformal coating to everything. Maybe you can be luckier with temperature: if the device is buried somewhere it will reasonably stay far from the outside high and low \$\endgroup\$
    – LuC
    Mar 9, 2023 at 16:44

9 Answers 9

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A gravity-battery might be designed to drop a weight, generating energy, when the time-capsule's opened.

A gravity battery is a type of electricity storage device that stores gravitational energy, the energy stored in an object resulting from a change in height due to gravity, also called potential energy. A gravity battery works by using excess energy from the grid to raise a mass to generate gravitational potential energy, which is then dropped to convert potential energy into electricity through an electric generator. Energy generated from a gravity battery is a form of sustainable energy. One form of a gravity battery is one that lowers a mass, such as a block of concrete, to generate electricity. The most common gravity battery is used in pumped-storage hydroelectricity, where water is pumped to higher elevations to store energy and released through water turbines to generate electricity.

"Gravity battery", Wikipedia [links and references omitted]

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    \$\begingroup\$ This was my second thought. First thought was springs. A compressed metal spring should be able to store energy for a long time and could be smaller/lighter than a gravity battery. \$\endgroup\$
    – Michael
    Mar 9, 2023 at 8:47
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    \$\begingroup\$ Over the space of 100 years, a metal spring would certainly lose some of its energy - would need a decent metallurgist to quantify how much. \$\endgroup\$
    – MikeB
    Mar 9, 2023 at 17:44
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    \$\begingroup\$ I fail to see how a battery is needed in the first place - an electric motor can be stored in a dry place or even in vacuum for 100years and a spring + crank is enough to make it run for the duration of the product's use in the future. It all depends on how much power is needed, but again no long-shelf-life battery should be expected to have a lot of power capability. \$\endgroup\$ Mar 9, 2023 at 23:57
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    \$\begingroup\$ All the answers are good, but I've decided to accept this one because I like the "frame challenge" and potential energy seems like a better bet as long as we can seal up the mechanical bearings well enough to make sure they'll still spin. \$\endgroup\$
    – Theodore
    Mar 21, 2023 at 21:06
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The longest operating battery: https://en.wikipedia.org/wiki/Oxford_Electric_Bell

No exotic chemistry required, but it's very effectively insulated so as to prevent self-discharge.

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  • \$\begingroup\$ Thanks for that! that's the sort of thing it would be really good to not knock over and smash. \$\endgroup\$
    – Fattie
    Mar 9, 2023 at 1:33
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    \$\begingroup\$ Except they don't know what the battery is made out of \$\endgroup\$
    – Nelson
    Mar 9, 2023 at 4:18
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    \$\begingroup\$ Been ringing since 1840. Or perhaps 1825. \$\endgroup\$
    – D Duck
    Mar 9, 2023 at 21:12
  • \$\begingroup\$ The don't know for sure but suspect that it is a Zamboni pile. \$\endgroup\$ Mar 11, 2023 at 9:18
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Industrial Zinc-air batteries have a very long shelf life. They need to be activated (pull-tab) and require an oxygen environment which may invalidate this battery for your needs.

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    \$\begingroup\$ You have to hermetically seal them against oxygen. I came across a box of zinc-air hearing aid batteries ~15 years old and they were all dead. \$\endgroup\$
    – user71659
    Mar 9, 2023 at 5:52
  • \$\begingroup\$ @user71659 Zinc-air coin cell batteries have a shelf life of approximately 3 years. It's the reason I stated "Industrial" as those batteries supposedly have much better sealing. \$\endgroup\$
    – qrk
    Mar 9, 2023 at 16:54
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    \$\begingroup\$ Issues aside, stating something has a "very long shelf life" without addressing whether than covers the OP's stated 100-year requirement doesn't mean anything. \$\endgroup\$
    – chepner
    Mar 9, 2023 at 17:24
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A nuclear-diamond battery is probably the best choice, they could last for 100's of years.

In 2018, researchers from the Moscow Institute of Physics and Technology (MIPT), the Technological Institute for Superhard and Novel Carbon Materials (TISNCM), and the National University of Science and Technology (MISIS) announced a prototype using 2-micron thick layers of 63Ni foil sandwiched between 200 10-micron diamond converters. It produced a power output of about 1 μW at for power density of 10 μW/cm3. At those values, its energy density would be approximately 3.3 Wh/g over its 100 year half-life, about 10 times that of conventional electrochemical batteries.[6] This research was published in April of 2018 in the Diamond and Related Materials journal.[7]

Source: https://en.wikipedia.org/wiki/Diamond_battery

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  • \$\begingroup\$ There's at least one company trying to commercialize these batteries. \$\endgroup\$
    – brhans
    Mar 8, 2023 at 17:51
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    \$\begingroup\$ Difficulty: current outputs measured in nA. \$\endgroup\$ Mar 9, 2023 at 0:51
  • \$\begingroup\$ @hacktastical for the coin cells, if you had to you could stack 1000's of them I guess. I think a TEG energy harvester or RF might yeild better results. Even a solar cell to supplement would be good \$\endgroup\$
    – Voltage Spike
    Mar 9, 2023 at 1:43
  • \$\begingroup\$ This is just a miniature Radioisotope Thermoelectric Generator / beta-voltaic battery. \$\endgroup\$
    – IronEagle
    Mar 11, 2023 at 16:18
  • \$\begingroup\$ The nuclear batteries do a direct conversation with electrons \$\endgroup\$
    – Voltage Spike
    Mar 12, 2023 at 3:04
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Thermal batteries (an unfortunate name because they are not hot until activated) are used in military applications such as missiles. They are activated by a built-in pyrotechnic charge and have an advertised shelf life of 50 years. It's not hard to imagine a greatly extended shelf life through improved sealing.

They typically produce a great deal of electric power for a relatively short amount of time, such as the amount needed to steer a missile using strong servo motors. Since you need lower currents, you could combine a thermal battery that runs for a few minutes together with a supercapacitor for long duration, low power use.

To activate, you could pull a pin that allows a spring-loaded hammer to strike an internal primer. Within milliseconds, great gobs of power would be flowing to charge your supercapacitor.

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  • \$\begingroup\$ I wouldn't advise any electrolyte-based capacitor: within a few years of shelf life, they become unusable. Even a humble MLCC can pose a risk, soaking too much water from the ambient. \$\endgroup\$
    – LuC
    Mar 9, 2023 at 16:34
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    \$\begingroup\$ +1 This is the answer for current-day demands that look like this. Molten-salt batteries can have runtimes of hours (limited by the pyrotechnic charges keeping the salt liquid, you could chain them to get even longer runtimes), provide many amps of peak current, and have a certified shelf life of 20 or 50 years for weapons. You could design them for 100-year storage. \$\endgroup\$
    – Mark Omo
    Mar 10, 2023 at 4:33
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Let's assume we're talking an Earth-bound solution. If the location has a consistent ambient thermal gradient available, and your power needs are low, perhaps a thermopile combined with some energy-harvesting + storage setup could work. This is kind of like using a radioisotope thermal generator (RTG) as used in spacecraft, but without the hazardous material risk (not to mention the government red tape in obtaining such a device.)

An idea that could provide round-the-clock power:

  • Day harvesting - lensed solar to heat the thermopile hot side, cool side in the ground
  • Night harvesting - ground-source heat to the hot side, cool side in air

Challenge: thermopiles are very inefficient (about 7.5%.) But with a large enough pile and big enough gradient you can get useable power. Piles sold for use with woodstoves generate hundreds of W. More about those here: https://www.tegmart.com/


Now, if the requirement is that the device have a means to power itself when opened, but otherwise isn't powered on, then why not solar? With the cells protected from the elements until the capsule is opened, the cells will not age like they do when exposed to light and heat.

Likewise, a wind or water turbine, hand crank, or some other electromechanical generator could generate power. There's kind of a neat wind approach that uses a single, flexible blade: https://www.bridgestone.com/bwsc/stories/article/2019/11/13-2.html

Finally, I think power supplies that use a triggered chemical reaction are problematic for long term, because of shelf life. That said, an 'idiot-simple' solution could be a lead-acid battery that has its electrolyte separate. Open the capsule, pour in the electrolyte and you have a pretty big battery at about 50% state-of-charge.

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I would try going back to basics and supply the separate parts to make a Voltaic pile: copper and zinc plates, cardboard separators and salty brine along with instructions. You could scale the electrode area and stack height to get the required current and voltage for your load.

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  • \$\begingroup\$ Anything with electrolyte stored separately will do. Dry substances are extremely inactive. \$\endgroup\$
    – fraxinus
    Mar 10, 2023 at 7:18
  • \$\begingroup\$ yes, lead-acid for instance can be stored dry. and easily rehydrated. could be an easy win if the electronics can run off a single 2V cell. but only slightly more complex more voltage is needed. \$\endgroup\$ Mar 11, 2023 at 23:56
  • \$\begingroup\$ +1 for volta pile if power demands are low. There are examples of Zamboni plies that are still working centuries after they were sealed.... en.wikipedia.org/wiki/Oxford_Electric_Bell \$\endgroup\$
    – bigjosh
    Mar 15, 2023 at 1:25
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Thinking out of the box here: does the energy really have to be inside of the "battery"?

Maybe include a solar panel hooked up to the device, along with instructions for the future users that they need to place it in sunlight?

Or... if you expect there not to be any sun anymore by the time they discover the time capsule: a dynamo with hand crank, along with instructions that they should spin the crank?

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  • \$\begingroup\$ Ah, but what if they can't read? \$\endgroup\$
    – Theodore
    Mar 9, 2023 at 19:44
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    \$\begingroup\$ @Theodore you can always use pictograms, symbols or drawings. I mean... we can understand what 10.000 year old cavedrawings depict, right? \$\endgroup\$
    – Opifex
    Mar 9, 2023 at 22:07
  • \$\begingroup\$ We can recognize an ice-age painting of a buffalo as being a buffalo, but if the paintings at Lascaux were directing us to do something specific, I think we missed out. \$\endgroup\$
    – Theodore
    Mar 21, 2023 at 21:03
  • \$\begingroup\$ @Theodore The cave paintings hold a message. They tell us a story. Not instructions. We can clearly see the story they are telling: it's them hunting animals. Now, if you add pictures of a human (can be a drawing or even a photograph) doing whatever is necessary top use the device, then any futuristic civilization will be able to figure it out. \$\endgroup\$
    – Opifex
    Mar 21, 2023 at 21:27
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Not exactly a "battery" but for the application, a fuel cell might work well. Use spring energy to puncture sealed tanks of hydrogen and oxygen, and a moment later a second mechanical device creates a spark, and your fuel cell roars to life. Once it's operating & producing power, an electronic controller could throttle the feeds to regulate the output.

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