Panasonic, Sony
My Panasonic R4, which I like very much, loses battery power within a day if the battery is attached and the computer is off, even though the charged battery lasts for 5 - 7 hours. For traveling, I disconnect the battery and it holds its charge quite a while.
My prior Sony Vaio (FX series?) battery didn't lose the charge in a noticeable way when connected to a turned off computer. The off-label extra batteries I bought held the charge less well than the ones from Sony.
Sylvia