Lies, damned lies, and equipment specs. I can print up a lovely sticker that says it'll output 1000A. Doesn't mean it'll output that.
It's significantly cheaper to make a low-power supply than it is to make a high-power power supply. Making the latter means you need a bigger transformer (with heavier windings), larger capacitor(s), larger inductor(s) and higher current rectifier(s), all of which add up to more money. If you're trying to make stuff on the cheap and aren't worried about pesky things like ethics, you'll go with the lower end components and massage the specs (by testing at low temperatures, etc. This is especially common with computer power supplies which specify output at 25C, even though they would actually operate at ~40C unless you're using them inside a refrigerator), use theoretical values rather than actually testing the product (saving money on QA), or just outright lie about the specs, the latter of which is probably the case with this charger, for reasons below.
One big red warning light that your charger is substandard is that the CE mark (which is used to indicate conformance to EU standards) is fake. The shape of the letters and their spacing is wrong. A real CE mark should have the letters each forming a half-and-a-bit circle and should link up if you continue the arc, as shown below. A cursory glance at the mark on your charger shows it looks nothing like this.
The CCC mark (indicating compliance to Chinese standards) is also fake.
Other warnings signs include having no manufacturer listed and improper capitalization (should be mA, not MA, unless they're claiming is can supply a billion amps.).
In essence, to determine if a charger is likely to be substandard, apply the same thoughts as you would for determining whether a product is counterfeit. The only real difference between a substandard product and most counterfeits is whether a manufacturer's label is forged or not.
P = V*I(1) can also be rewritten as
P = R*i^2(2) and
P = V^2/R(3). Let's say that C is the charge of battery,
C = P*t(4), so with (3) and (4) we have
C = t*V^2/R(5) =>
t = R*C/V^2(6).
Ris the resistance of cable (thin wires are more resistant, so time to charge will be longer);
Vis the voltage given - more voltage, less time; if you are using those 'xing-ling'-generic-power-adapters, they would rectifies AC network voltage improperly, so effective voltage given would be less than original power adapter voltage and time would be larger...
R = r*L/Athat depends on length of cable
Lwas bigger than other cables...