There are a lot of cheap USB convertor that can use in the car to connect into the in car power point. I do that everytime with my HP iPAQ last time. It works perfectly on others USB chargable phone. BUT not iPhone!!!
Please make sure you only use the dedicated car charger from Apple store, which cost you about rm80-100. Else you may kill you iPhone instantly, base on your luck that day. One of my lucky friend burned his iPhone on the second weeks after he start using his lovely phone this way. He sent the iPhone all the way from Malaysia to China to find “expert” to fix it, but at the end, he get back the phone and have to keep it into store room (not willing to throw since it is too expensive to use only for 2 weeks). The “expert” told him that the mainboard of the iPhone burned, if he want to fix it, he need to replace it with ~rm1k++, he choose not to go for that. Since with that price, he can get another iPhone.
So, please make sure you use the correct tool. iPhone, is not a normal phone, at all.
Thank you for reading.