Sure if you need the phone for something urgent you have a low battery and if you play or have time to entertain you have loaded in your memory card or from online. If you do not want to even think about it first here are a great idea, iSun, is a solar charger that incorporates a battery or 1.100mAh 2.200mAh, depending on model.
You can charge up to two mobile devices, which makes it something to keep in mind not to run out of power for any situation. Thanks to solar energy is a great choice for a family trip or excursion, which gives some security.
Wired with virtually any mobile phone market whether they are old models and the latest, so you will not have problems putting your mobile device to pay for your trip.