I think you're being too literal. 100% faster, in this context, means you cut the time in half. Definitely not the correct usage though. For instance, saying "That shirt is 100% off" when you mean "that shirt is half off" is really bad form.
If you see that battery $x$ is charging $b$% faster, which as a proportion is $p=1+{{b} \over {100}}$, what is meant is that the new battery charging time $x_1$ multiplied by the derived proportion $p$ yields the original batteries charge time $x_0$. In math symbols,
$$x_0=x_1 \cdot p$$
$$\Rightarrow x_1={{x_0} \over p}$$
The original battery charges in 5 minutes, and you get a method to charge the battery 100% faster, you get,
$$x_1={{5} \over {p}}={{5} \over {1+{{100} \over {100}}}}={5 \over 2}=2.5$$
Which gives a charge time of two minutes and thirty seconds.
Basically, when you're in the "wild", the real world, you have to give people some leeway in how they use mathematical jargon. Don't even get me started on the use of the words integral and integrated in common usage...
Fun Fact: $-5$ minutes means you travelled back in time...
100%
means100%
discount - free give away? No? Let's say it cost$10. 90%
off would be$9
off - it would cost$1. 99%
off would be it cost10
cents. 99.9% off is 1 cent.100%
off is$0
.200%
off is they pay me$10
? No? $\endgroup$