Yeah, the way they're presenting it is silly. C-14 decays to N-14 with a mass defect of 156.5 keV/c^2. With a half life of 5730 years, 1 kg of carbon-14 will pr

Yeah, the way they're presenting it is silly. C-14 decays to N-14 with a mass defect of 156.5 keV/c^2. With a half life of 5730 years, 1 kg of carbon-14 will produce 1.6×10¹⁴ decay events per second. That's 3.8 W/kg specific power, which is roughly 1% of lithium ion -- assuming 100% conversion efficiency. HOWEVER, we know that only 31% of the decay energy is actually carried away by the beta particles, and the rest ends up as heat (which is not captured)[1]. On top of that, the efficiency of converting the beta particle's kinetic energy into electrical power is low. I found a paper citing a 26% conversion efficiency [2], which seems high but lets go with it. Finally, the mass of the battery obviously includes more than just the C-14. Lets assume that half the mass of the battery is C-14. That would bring us down to 300 microwatts per gram of C-14, and less than 0.05% of the specific power of a LiIon battery. [1] There's also a positron that shares half of this energy -- I don't know if these devices capture that, so I'm just leaving it in. [2] https://www.sciencedirect.com/science/article/pii/S016890022... https://www.sciencedirect.com/science/article/pii/S016890022...)