Thinking through this, it seems to me the pod will not need batteries, or at least not a significant number. They will only be needed when the pod is at rest.
During motion, the pod is traveling on a magnetic field. Cut that field with a coil to product all the power required by the pod in motion. Since propulsion is produced externally to the pod, the requirements for electricity in the pod during motion will be almost statistically insignificant.
I’m not in any way saying there are not a lot of hurdles. But I don’t think power in the pod will be a limiting factor in capacity.