Your phone has circuit that handles internal battery charging. It will regulate the amount of current needed, not the E-Werks. If your phone can handle 1.5 A then it will source that and taper off as the battery charges. If you have the E-Werks setting on 0.5A then it will never take much longer to charge. Put it to max setting and charge.

Think of it this way, your residential wall outlet (in USA, as the example) is typically protected by 15A breaker. Plug in a 40W light bulb. The bulb will not draw enough to trip the breaker. It only sources what is needed. Same with any of your electronic devices.