Q: battery light came on while driving; alternator or battery issue

The battery/charging warning light could pertain to the battery, the charging system, wiring faults, or even a loose drive belt that is not properly driving the alternator. The exact circumstances would have to be determined by looking at the car. If the battery is in good condition, the car should start readily no matter what the weather is. If your battery is 4-5 years old, it is possible your battery needs to be replaced. If you want to have the issue resolved right at your location, simply request a battery load test. Batteries are very important and if the battery only has a marginal pass on the load test you should just simply install a new battery to reduce diagnostic headaches. The mechanic who tests the battery will also test the charging system and otherwise determine exactly why the battery/charging light has come on. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.