How long does a car battery last?

A conventional lead-acid car battery generally lasts three to five years, and the biggest variable is heat, not cold. High temperatures accelerate the internal chemical degradation and evaporate electrolyte, which is why batteries in Arizona and Texas routinely fail years earlier than those in Minnesota. What cold does is expose an already-weakened battery: low temperatures reduce available cranking power while thickening engine oil and raising the effort needed to start, so a marginal battery that survived summer dies on the first hard freeze, which is why failures cluster in winter and get blamed on it.

The warning signs are worth heeding because the failure mode is being stranded. Slow or labored cranking, headlights dimming noticeably at idle, needing a jump more than once, and a battery over four years old are all reasons to test rather than wait. Most auto parts stores test batteries and charging systems free in a few minutes, which also distinguishes a dying battery from a failing alternator, since the symptoms overlap and replacing the wrong part is a common expensive mistake. Habits that shorten battery life: frequent very short trips that never fully recharge it, leaving accessories drawing power, corroded terminals, and long periods of sitting unused, which is what a trickle charger or battery maintainer solves for seasonal vehicles.