
NanoTritium 20-Year Betavoltaic Battery - peter_d_sherman
https://citylabs.net/products/
======
gpm
I'm not an electronics person, but as I understand it this amount of energy is
typically harvestable from ambient rf in populated areas.

See the first few paragraphs of this paper for a bunch of references:
[https://www.ntu.edu.sg/home/nprivault/papers/ambient_harvest...](https://www.ntu.edu.sg/home/nprivault/papers/ambient_harvesting.pdf)

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smoyer
I think these are awesome ... I've got an application for a very low duty-
cycle device (operates for seconds each hour) and, paired with a suitable
capacitor (or super-capacitor), I can completely pot the entire system in
epoxy, mount that in foam in a tennis ball and still have about a decade long
service life!

EDIT: No, it's not a dog toy

~~~
cwkoss
If it's inside a tennis ball, it only stays not a dog toy as long as you keep
it away from the dog.

~~~
zentiggr
And given my dog, it'd stay a dog toy for a very short half life after me got
to it.

Nothing less than Kong toys in his world, everything else is a snack.

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Sophistifunk
I just want a sealed, finned RTG I can drop in the deep end of my pool and
forget about.

~~~
kevin_thibedeau
Doable with Americium. Start hoarding old fire detectors.

~~~
ben_w
Those things are only around 30 nanowatts each.

[https://en.m.wikipedia.org/wiki/User:BRW/images#/media/File%...](https://en.m.wikipedia.org/wiki/User:BRW/images#/media/File%3AAmericium-241.jpg)

[https://www.wolframalpha.com/input/?i=5.4+MeV+*+33000%2Fs+in...](https://www.wolframalpha.com/input/?i=5.4+MeV+*+33000%2Fs+in+nanowatts)

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gliese1337
What is the point of a 40-pin connector when the spec sheet only indicates
that two of them are used (exactly as one would expect for a battery)?

~~~
Nextgrid
Mounting? You solder all 40 pins to hold the device onto the board even if you
only need 2 pins. Presumably the pins are repeated across all sides so you can
pick any pin that makes routing more convenient.

~~~
gliese1337
That would make sense, but according to the spec sheets the pins are not
repeated--only two of them are functional, the rest are dead.

~~~
Nextgrid
Seems like an oversight that can be easily fixed.

~~~
jdsully
Saves them money on packaging costs. Wire bonding isn't free.

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ajnin
This is cool stuff but I'm not sure what application this is targeted at.
Primary lithium cells have a 15 to 20 years operating life, and contrary to
those batteries you can draw more power on demand when you need it and stay
asleep at low current the rest of the time. Energy density seems higher but
not that much.

~~~
gpm
15 to 20 years operating life on a single charge? Or 15 to 20 years operating
life if you recharge them occasionally?

~~~
SAI_Peregrinus
"primary lithium cell" means a non-rechargeable lithium battery.

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russdill
Lithium batteries already beat this on every metric and aren't exotic.
[http://www.tadiranbat.com/long-life-xol.html](http://www.tadiranbat.com/long-
life-xol.html)

~~~
gitgud
I'm pretty sure Lithium batteries don't produce continuous power for 20
years...

~~~
dogma1138
Non rechargeable cells can have that lifetime.

~~~
zaarn
I doubt at -40C to 80C.

~~~
dogma1138
Then you doubt for no reason these ones form Energizer are -40 to +60c..

[https://data.energizer.com/PDFs/lithiuml91l92_appman.pdf](https://data.energizer.com/PDFs/lithiuml91l92_appman.pdf)

And quick googling shows batteries with a wider positive range.

~~~
zaarn
If you scroll through that PDF you'll notice the temperature capacity chart.
At -40°C you're going to have to limit your power drain a lot to get rated
capacity. At low temperature the chemical reactions get too slow to take
advantage of the full capacity of the battery, that's simply a reality you
can't get around.

A "betavoltaic" would deliver full rated capacity at any temperature,
regardless of changes or duration.

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mdorazio
Are these actually being sold now? I first saw these advertised by citylabs
years ago with vague wording on availability and maybe-pricing in the $3k
range.

~~~
arcticbull
My understanding is there have been betavoltaic cells for a long time, and
with improvements in semiconductor manufacturing technology, they've been able
to move towards less radioactive materials such as the tritium used by
citylabs. These things exist, but of course, tritium is not cheap.

~~~
galangalalgol
Strontium 90 seems like a good candidate. It and what it decomposes into are
both pure beta emitters. Beryllium 10 also looks good, though very low power.

Someone recently used nickel 63 too.

~~~
arcticbull
> Someone recently used nickel 63 too.

Yeah the Russians, right? ([https://newatlas.com/nickel-nuclear-battery-
design/54884](https://newatlas.com/nickel-nuclear-battery-design/54884))

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gaze
If these are going on IoT/Sensor network devices, doesn't this add to the
e-waste issue? A lot of these sensor devices are never recovered. Now we have
radioactive e-waste.

~~~
ISL
It adds to the e-waste issue if the device is ground up or burnt.

Some, but not all, of the properties of tritium are somewhat friendly. The
half-life is comparatively short at 12.5 years, so it isn't left for future
generations. It is a beta-emitter, so shielding is straightforward. The
daughter, helium-3, is quite benign. It can be readily encapsulated (see
tritiated key fobs).

If it does get loose from encapsulation, it goes everywhere that hydrogen
goes, which is largely everywhere. On the plus-side, gaseous tritium mixes and
dilutes quickly in the atmosphere. The key is not to ingest concentrated
quantities of it. The decay energy is very low, which makes assaying for
tritium contamination quite challenging.

If you're looking for e-waste of radiological concern, americium smoke
detectors might matter more. I'm not sure.

~~~
gaze
Maybe someone throws a handful of these into a grinder to harvest prescious
metals or something. Grinder cracks the encapsulation of like 10-20 of these
in sequence with an operator standing nearby. Now is it an issue?

~~~
darkmighty
Hydrogen diffuses very quickly. I would imagine no issue. There could be an
issue if it were to burn, then the inhaled water could linger in your system
for a while (although water is constantly excreted too). But then the dosage
is so small, and it's alpha radiation (readily absorbed by nearby water
molecules). Sure you would get a better estimate by running some calculations,
but I suspect the dosage even of a handful of those totally inhaled as water
vapor would be sub-background.

Compare it to mercury (which some years back was still in batteries), which
evaporates easily when heated, stays in your body for very long times (and is
cumulative), and has clear neurological impact.

I wouldn't worry about even a large number of those breaking.

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p1mrx
For context: 50 microwatts * 20 years = 9 watt-hours, comparable to an 18650
cell.

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jacob019
So 1000 of these and I can power a 1W LED. But after 20 years it will only be
0.3W. This is comparable to RF power harvesting. What are the use cases for
such minuscule amounts of power? Remote sensors?

~~~
simcop2387
Pacemakers and remote senors are some of the big ones I know of. Though I
don't know if modern pacemakers use them still.

~~~
dole
“In the past, small "plutonium cells" (very small 238Pu-powered RTGs) were
used in implanted heart pacemakers to ensure a very long "battery life". As of
2004, about ninety were still in use. By the end of 2007, the number was
reported to be down to just nine. The Mound Laboratory Cardiac Pacemaker
program began on 1 June 1966, in conjunction with NUMEC. When it was
recognized that the heat source would not remain intact during cremation, the
program was cancelled in 1972 because there was no way to completely ensure
that the units would not be cremated with their users' bodies.“

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agumonkey
There are quite a few videos on youtube (nerdrage ? forgot) where people use
light radioactive material to energize photovoltaic cells.

~~~
toomuchtodo
Poor man's RTG. Love it.

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bigiain
This seems infinitely more plausible that this, which was doing the rounds
last week:

[https://ndb.technology/](https://ndb.technology/)

“Releasing 3600 _whole_ electrons! Or even 14400!!!”

(That’s about a billionth of a 1 pico farad capacitor discharging. I suspect
you need some reasonably exotic laboratory equipment to even detect 14400
electrons...)

~~~
zackbloom
God that website is terrible. It is so incredibly redundant about the value of
infinite power, as if anyone would need an explanation as to why infinite
energy would be useful, but gives so little detail or explanation about what
the device actually is.

~~~
pjc50
Absolutely screams investor scam to me.

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csours
What kind of battery/capacitor could you make with lithography/chip making
techniques? Genuine question. I know there was an announcement about this
recently. I know it would be far more expensive than the roll of tape that
current lithium batteries use, but I have to imagine that Apple is working on
this for the iPhone/etc

~~~
Reelin
Is this the recent announcement you were thinking of?
[https://xnrgi.com](https://xnrgi.com)

~~~
csours
Maybe. I thought I saw something from IEEE; it may have been this company.

edit: Looks like yes: [https://spectrum.ieee.org/energy/the-smarter-grid/the-
return...](https://spectrum.ieee.org/energy/the-smarter-grid/the-return-of-
the-lithiummetal-battery)

edit again: also this from 2017
[https://spectrum.ieee.org/semiconductors/design/how-to-
build...](https://spectrum.ieee.org/semiconductors/design/how-to-build-a-
safer-more-energydense-lithiumion-battery)

~~~
Reelin
It's the only one I know of applying standard semiconductor wafer techniques.

If it works out, I think this one
([https://spectrum.ieee.org/energywise/energy/environment/a-gl...](https://spectrum.ieee.org/energywise/energy/environment/a-glass-
battery-that-keeps-getting-better)) is a more promising battery technology in
the long run due to lifespan. It appears to be far more preliminary at this
point however.

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tlb
Tritium's beta decay process emits electrons with 5.7 keV energy. I wonder why
these devices output such low voltages as 2.4 V. A beta decay electron should
be able to jump to a cathode at nearly -5700 volts.

~~~
baybal2
Very likely they have some integrated voltage downstepping.

Doing 5.7kV circuits is not your typical power engineering 101

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bigiain
So who’s gonna be the first to order, like, 400 of the 100 micro watt ones, to
power a RaspberryPi web server for 30 years? (Which will, of course, have
trashed it’s flash memory by Xmas...)

~~~
varjag
if by 400 you mean 40000

~~~
bigiain
Ahh yeah. _Almost_ within an order of magnitude... (Good enough for government
work, right?)

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slumdev
I mean this question at face value because I don't want to be _that guy_ \--
what are the applications?

This seems like a very small amount of power with very specific and unusual
benefits over other power sources.

~~~
opwieurposiu
One use is in military/aviation radios to keep encryption keys in sram. The
power can be disconnected and the key wiped in the event of a crash or
impending enemy capture. If the key was in flash it might be recovered.

~~~
baybal2
How do you know that?

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ISL
Pricing?

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ortusdux
I keep hearing conflicting information on the legality of importing tritium
into the US. Is it controlled? Is it legal to import?

~~~
post_break
I have tritium keychains from china. Probably not legal but aliexpress or
wish. For the gun sights trijicon is the only game in town to get tritium
installed.

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BrionyAbbot
Cool, but if you use Carbon-14 you get more microwatts and thousands of years.

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rtkwe
So what are some actual uses for these at such low power?

~~~
xnyan
Besides what’s in the article, some Bluetooth low energy SoCs can operate on a
power budget of less than 50 µA. Also keep in mind that with components like
super capacitors, power can be “charged up” (very roughly like filling a large
bucket with a small water hose so you can get one big toss of water) in order
to get a larger pulse of power.

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Trias11
... medical implants...

Powered by radioactive battery?

~~~
cperciva
Sure. Tritium releases very low energy beta particles; even a thin casing will
render this safe.

~~~
jjtheblunt
I could swear that, as a kid near Chicago in the early 1980s, I had a tritium-
backlit Timex or Casio digital watch.

That said, I can't find it online...and gave it away decades ago.

~~~
dole
I could be wrong but tritium on watches usually wasn’t typically used on the
face itself, but in gas tubes or vials on the hands and hours markers. Ball,
Marathon and Luminox are three popular watch brands that use them currently.

Evidently radium stopped being used for lume in 1970, and while tritium faces
may have been a replacement around that time, tritium as used only has a
lifespan between 12-24 years.

~~~
SamReidHughes
Tritium was commonly used in luminescent paint on mainstream watches (Rolex,
Omega, et al) until the late 90's/early 2000's.

