iPhone 7 battery discharges very fast after using Waze and charging 3 hours from the car
If the USB Car charger doesn't have the MFi (made for iPhone) logo then it is probably a cheap charger with minimal over-voltage protection circuits inside, even if it says Philips on the outside. This can cause damage to the charge circuit on your phone's logic board and ultimately your battery. 

Waze really sucks the juice out of a battery and having that charger on for 3-4 hours straight may have damaged your phone. Try running your phone inside and charging with an Apple original wall cube to see if that makes a difference. If not, then you will need to have that phone looked at by either Apple or an independent micro-soldering repair shop.