My Lexus’s alternator drops voltage to between 11.5-11.95 ( via volt meter) after shopping store to store for an extended period of time during the day. However, when it cools off by not driving it for an or or two, it charges normally. .Time for a new one?
It may be time for a new alternator. It should be checked on the bench to confirm it is the actual problem but parts stores have the machines to test them.