I have an old Sony Vaio laptop (PCG K215B) whose battery no longer retains charge for more than a few minutes. Question: is it safe to run the laptop without the battery installed? Or is the battery used in some way by feedback circuitry (rather like a super-capacitor) to control the supply voltage from the mains-powered brick? I don't want to risk over-volting the laptop, nor do I wish to lose any user settings if the battery is relied on for data retention.