Am I misunderstanding something here? The article reference Nickle-63, us also references 63 isotopes? The Nickel-63 would decay into copper but the half-life is 100 years…not 50, so there would still be radioactive material after 50 years. As a by-product of the decay wouldn’t it also emit low-level gamma?
Yes. The ‘battery life’ is measured by the battery’s ability to produce the necessary volt/amps necessary to sustain the load.
At 50 years, I assume that the decay has used up the amount that makes the battery no longer useful.............