Will I damage my Android device by charging it using a generic microusb + car adapter?
USB, mini-USB, and micro-USB cables are standardized, the voltage and amperage are the same across all standard compliant USB chargers. As long as the charger is a standard, generic micro-USB charger then it should be alright.

That doesn't make it impossible for a manufacturer to create a non-standard plug that looks like a USB plug, but they're pretty much screwed up if they do so.