Make your own charger for your phone. There are many ways to do this, in this projection I will show you how to do this using the LM2596. The advantages of this charger are charging current of 3A, simplicity in the making, input voltage 7v - 40v. It can power directly from the 12v or 24v battery. In this example I used a 14.4V battery from a cordless drill.
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Step 1: Components
Step 2: Schematic
Schematic of USB charger.