Overcharge a sealed 12V lead-silver-calcium battery with a power supply to prevent sulphatation
Are you sure you are doing everything correctly?
Is the battery old? Does it get really hot when charged normally with your ctek charger? Do you have any Current/Voltage graph for its charging?
Batteries dont charge just from pumping a voltage on them, they use contant current and constant voltage at some point every time they get charged using their normal charges. Using your power supply may damage the battery.
You dont want to use your power supply and make the battery blow up on your face.
I would suggest getting a proper charger. If the ctek charger is designed for this kind of battery, this means it charges it correctly. After many uses of a battery, the Vmax may start to drop, so you wont get all those 14.8V after many charge cycles.
After all, 0.1V for a 14.8V battery sounds (and it is) vary insignificant.
Batteries have chemicals in them, you cant expect them to be perfect and charge up to a certain voltage. Maybe if you let your battery for a while after charging it with your ctek, it will go up to 14.8V on its own (by cooling down lets say)