I used my Monoprice charger again running Navigation and Pandora. The first time i tried it it charged the battery and the charger was hot to the touch. The second time it did not and the charger itself was cool to the touch telling me it was not working. This time I started with around 68% charge and ended around 76%. The charger was again hot to the touch. In all three tests the Pre showed the charging icon. So at least for the Monoprice chargers, they work to charge the phone with Navigation and Pandora running, just check the charger for heat!