I have a 99 Nissan Quest. Replaced battery 4 times in two years. Some of them hada dead cell. Yesterday battery died again and had it charged. Instrument panel warning light flashing for the battery, brake. Although battery is fully charged by shop can there be another reason for the lights to flash other than a bad alternator? Thank you

Has to be the alternator, you can determine if it works by putting in a known good battery, checking voltage when running-it should be at least 13.8 volts at the battery with the engine running. If not you can check the alternator output at the rear of the alternator itself-there is a post, it is positive, use the meter to check here. If you get low voltage here (less than 13), you know it is the alternator.