are car batteries ac or dc

Car batteries are DC, plain and simple.

Most passenger cars use a 12 V DC system (trucks often run 24 V DC, and mild hybrids add 48 V DC) because starters, ECUs and lights prefer one-way current.

The alternator actually makes AC, which is rectified to DC to charge the battery and run the electrics.

EVs carry high‑voltage DC packs, then use inverters to feed AC motors and even 240 V AC power outlets. So DC runs the show; AC just guest-stars backstage.