Alternator Performance of Gli 2015

I have two cars at my home, Corolla and EFI Cultus and I had to park them at my home when I went to my hometown by train. When I came back after nine days and tried to start the cars but I found that the cars are not started. I was going to ride in Corolla but on starting I found that battery gave noise I installed the Daewoo maintenance battery and it gave the indicator of the status of the battery and it gave a green indicator. I thought that the car was switched off for 9 days and it was not started a single time so it might take some time to get hot and start. I also checked the Cultus and when I started it, it also started with little slow cranks I looked at the indicator and it was also green.
I got the help of the mechanic to get charged the battery of my Corolla and he asked me to come after some time to get your battery. When I went there after about 15 minutes I found that the battery was green. I install the battery of my Corolla and it started and it runs without any issues.
I decided to check the running battery volts in Corolla and it was already running and the kit was already running I hooked the multimeter to the battery and it showed 13.84 with no load. I also got the help of Google and YouTube to find the video on this particular niche. I tested the volt of my car with a full load and it showed 13.6 on full load.
At this point, I thought that the alternator is not charged and it struggled to charge the battery. After a few days, I checked the battery indicator of my car it showed white and it needs some charging as per their chart.
I thought that battery was not working properly to make the voltage at a low level so I got the new battery without delay and put the new battery in excitement I decided to check and I was surprised to know that the local voltages reached 13.7.
I tested this battery on my Cultus and it showed 14.3 volts without any load when I did the research, I knew that there was something wrong with the alternator charging system and I got the alternator voltage regulator, which was out of order. Then I contact the expert to get checked the alternator whether it is good o r bad. After checking with the battery load tester, he found nothing bad with the alternator.