Complementing onlooker's good post above:
Not only the batterizer did perform WORSE than a regular battery, it did fail to meet the first of its claims: to extract every last drop of juice from a battery (aka "chemical energy"), and Dave proved this failure on the live feed last night.
People - and here I include the so-called Batteroo engineers (engineers my ass!) - are unable to tell the difference between voltage and stored energy. Onlooker's example, a cell battery X an AA battery is a great example, does describe that very well, and one has obviously a lot more energy than the other, even although the voltage is the same.
A drop in stored energy doesn't necessarily mean a drop in voltage, and alkaline batteries are such an example: they present a flat 1.5V line until their stored chemical energy is way below a certain threshold. Bringing that voltage back to 1.5V is easy, but that doesn't increase the stored energy, because it isn't changing the chemicals of the battery in any way.
Again, increasing a battery's voltage doesn't increase the energy it holds: that cannot be changed on non-rechargeable batteries, and buyers of batterpoop should be aware of that. Voltage and energy are different things.