The idea of the body (more precisely: of the immune system – at this stage) as a battery is a disgustingly silly and technocratic idea; however, precisely for this reason it might be “catchy” among a significant portion of first-world populations, where everyone wants to perceive themselves as … a power drill!
The “charging” and “discharging” (of the battery…) seems to these unfortunate people like a good analogy of the Self (themselves) – Capital, which has fallen unconfessedly into a machine (“means of production / consumption”…). When “discharging” of the Self – Capital occurs, “charging” is needed which is not necessarily electrical. It can be chemical: various drugs, “nutritional supplements”, etc.
In the end it may also be biotechnological / genetic. The “transhumanism” emerges beautifully through innocent advertisements: and as machines you shall become…