Who’s in charge of the charge?

One disadvantage of using an old laptop to spare yourself the bother of loading all your usual programs on to a new computer is that it can sometimes do bafflingly stoopid things.
    Yesterday, when plugged in to the mains, it charged up to 26% and refused to do any more charging after that. I did a bit of messing about with the power settings, but nothing.
    So then I did what’s the option of last resort: I closed all the open programs and told it to switch off.
    And lo, when I started it up again, the bugger was deigning to charge the battery to a full top-up when I wasn’t putting much demand on it.
    All of which confirms that it’s not a case of you can’t win, it’s more that you’re not supposed to.