Hi love2ride222,
To start with - no new battery bought off the shelf will be fully charged. Our local new batteries (South Africa) are usually between 80 to 90 percent charged when it comes off the shelf. When only battery acid gets poured into a new battery it will never be fully charged - therefore a brand new battery actually needs to be hooked to battery charger if you expect it to be fully charged before installation.
On a normal car, truck, etc this hardly ever cause any problems, but in case of a scooter with DC CDI I am quite convinced that a new battery should actually be hooked to a battery charger before installation. The reason being - the voltage reading at a DC CDI itself must at least be about 9.6 Volts, otherwise the engine will not start.
Regarding your experience with batteries which didn’t work - I think there is a possibility that the batteries were not faulty, the batteries were perfectly normal. It probably came off the shelf without being fully charged with a battery charger before installation, therefore the voltage reading at the CDI was probably lower than 9.6 Volts when you tried to start the scooter. (If your scooter has a DC CDI)
To see if you have more than 9.6 volts at your scooter’s CDI , you can just remove the plug at the CDI, let somebody pull a brake lever, switch the ignition on, and press the engine “start” button. Then you need to do a Voltage test at the loose CDI terminal while e engine is swinging . One of the wires on that terminal is the power feed to the CDI, and if you get a reading of more than 9,6 Volts while the engine is swinging it means there is no need to worry about he battery - the problem could be at th CDI. ( This is in case your scooter has a DC. CDI).
If I remember correctly there are videos on Youtube about how to test a CDI, but I haven’t bothered to test one yet. I actually bought an extra CDI, just in case the CDI on my scoot start giving problems.
I have no experience about AC CDI’s - so in case your scooter has an AC CDI somebody else might be able to give advice.