2016 Accord EX had Check charging system light up on dash. Battery 6 mo.old at rest cold, 12.6v, while starting 11.2v, then triggers alt to charge, up to 14.3. Battery charged, drops back to the 12v range until alt triggered to charge again. Turning on headlights & brights triggers alt to charge. Turn off headlights & turn on a/c does not trigger alt to charge. Voltage drops to 12.2-12v & check charging system lights up on dash. Replaced Battery cable terminal sensor and ignition switch as I read that these do fail. What to check next? thank-you, Nick