Die Hard Battery Goes to 73% after full charge a few days later, Is this normal?

[1985 Century Mustang]

My battery is out of the boat and stored on a wooden shelf in my basement, every now and then I'll put a trickle charger on it to check, it seems to always drop down to 71-75% after I gave it a full charge a week prior. Water levels are good, the battery is a year old. Is this normal?. Shouldn't it be 100% or a little less if I'm not using it. Could the battery be defective? Your thoughts.

 

[1985 Century Mustang]

And before I charge it the meter reads 12.9 volts and usually around 73%.

 

[1985 Century Mustang]

 

[1985 Century Mustang]

Is this a decent battery. I thought Die Hard brand was good. If not what would you recommend.

 

[1985 Century Mustang]

And oddly enough when I finish charging it to 100% I'll put the charger back on right away and sometimes it shows only 85%

 

[alldodge]

And before I charge it the meter reads 12.9 volts and usually around 73%.

Give or take your meter, but 100% full charge for lead acid Bat is 12.7V

It's fully changed. Bat might read more then 12.7 when taken off a charger for a couple hours

 

[Scott Danforth]

I think your charger is the issue