I have a short micro USB cable that came with my bluetooth headset. It charges the headset just fine, but when I connect my phone to the same cable, using the same power source, it doesn't charge (no indicator, nothing). However, using the same power source with a different cable, the phone charges just fine.
What is it about the shorter cable that it charges certain devices but not others?
A portable device will accept charging source over USB connector when it sees certain "charger signature" at D+/D- pins. There are cost-reduced "charging cables" that have no pass-through D+/D- wires, but attempted to provide the "signature" insde the u-B mold, like shorting D+ with D-, which defines Chinese-style (or "dedicated charging port") signature.
If your phone doesn't understand this signature and expects something else (like motorola ID pin impedance, or QuickCharge), or your "short cable" doesn't provide what the phone expects, the phone will refuse to take charge from this cable. With a different cable and different source (which might have a different charger signature) your phone might be fine.
ADDENDUM: The BT device is a low-power device with a small battery. Charging the battery will require a very modest current, so the BT device doesn't care about higher power from USB port, and will likely rely on standard 100mA-500mA USB port capacity. So the dedicated BT charging cable likely doesn't have any "charging signature" at all, and that's why your phone refused to take the charge over the BT "short" cable.
There is the possibility, albeit remote, that there is a proprietary component in the way the USB plug is wired internally.
My first thought is that your issue is due to how the pins on the male USB side make physical contact on the two different female USB connectors.
In short, a cable doesn't always have the proper connection, and depending on the device, it may or may not accept it. The actual length of the cable doesn't apply to this.
USB generally come in two flavor, power(charge-only) and data-cable. From the outside, they look exactly the same. Also quality of cable does matter for some applications. 90% you may not notice it. This is why you can generally take one cable from one device and have it work with another device.
There are various reasons to why it won't work. Most point to type of cable. Here is some information on that aspect
You could, try powering the device from a computer power, and that ironically might work, or vise-versa with other devices.
