2. The Water Tower To Battery Analogy

When trying to understand electronics, it helps me to use a hydraulic analogy - in other words, using water and pipes as a stand-in for electrons and wires. What works for me, is to imagine a battery as a water tower, like this:

Begging the obvious, turning on the tap drains the water out of the tank, and the pump house refills (recharges) the tank. Each water tower may be a different height and size, yielding different characteristics such as pressure and capacity. So the analogy is: voltage=pressure, capacity=tank size, and current=flow rate. Think of the pump house as a wall charger and you are all set.

Different battery chemistries, by analogy, would correspond to different tank constructions: wall thickness, materials, shape, pressure limits, etc. Also, from a safety standpoint, consider that if you remove or add water faster than the tank can handle, you're likely to rupture the tank! And so it also goes with battery technology. Higher energy density batteries like Lithium-ion are like water tanks that are made to pack more water into the same space.

So that said, when you look at any notebook battery, you'll usually see a label or a spec that reads something like this:

Looking at this particular battery, it has relatively low voltage and high capacity compared to other batteries. If you imagine this battery as a water tower, think of a very low tower, with a huge tank. It holds a lot of water, but does not provide a lot of pressure. It is designed for a computer that requires relatively low voltage to operate, but that can operate for quite some time (capacity) before the battery must be recharged. This describes the Sony TX small laptop series perfectly.