Found this article on another site worth reading
here are several reason a new battery could prove out to be a "bad" battery:
- Someone could have removed the plug that blocks the battery vent letting out the gas that protects the battery from sulfating while it sits on the shelf. You have a new battery, but it is a "bad" battery.
- The lead structure that supports the plates and connects the cells together could have been damaged (broken) in transit or a cold solder joint develops in production. These high resistant internal connections will render a new battery a "bad" battery.
-The battery wasn't charged properly when it was put into service. If a battery isn't brought to a full charge when new, the plates will immediately begin to sulphate.
A lot of modern batteries feature a chemical process done during manufacture that allows the battery to be put into service with as little as 2 hours of charging time. In the past you had to charge a new battery at 1 ampere hour for each amp rating of the battery. So a 10 amp battery had to be charged for 10 hours before it was put into service.
Today, this type of battery with this feature, come 75% pre-charged and it only needs to be topped up to a full charge before being put into service. The shortcoming of this is the battery immediately begins to sulphate when you begin to add the acid and is rendered a "bad" battery in short order if you don't immediately charge the battery. After adding acid, and waiting the requisite 30 minutes, for the chemical action to subside you must charge the battery to a FULL charge. Even waiting 24 hours to charge one of these batteries can render them useless for use with an EI ignition.
-If the motorcycle's charging system cannot keep the battery fully charged, and the battery runs in a constant discharged state it will sulphate. This even though it appears that the battery is being charged. The reason you had to replace the old battery just might have been the charging system, not the battery.
Remember most of your past experience with batteries was with points. Points have no requirement as to the condition of the battery as long there is enough energy to produce a spark. All electronic ignitions have voltage requirements beyond what is required to run points.