I had a larger car charger, both sides rated at 1.0 amp, that I used for a couple of years to charge my phone while powering my GPS.  I bought this to keep the profile low and still be able to pull it out, but lthe GPS kept re-starting because it kept sensing that it lost power.  I went back to my larger charger wjhile I order the BoxWave Charger which my niece uses and I have testred.