Chi battery

I heard it said over the weekend that charging and discharging your dan-tien was similar to charging a battery. That analogy was flawed, as it is in fact the exact opposite. With a battery the more you repeat charging and discharging cycles, the weaker it becomes and it starts to lose its ability to hold charge. Where as with Taichi (and indeed most exercise) the opposite is true - the more cycles of training and rest you put your body through, the stronger you become. In other words the more you train (which is exhausting/discharging), the more you increase your body's ability to hold charge (or chi if you will).