I have an old PC 12volt that I would really like to use again so I've toyed with the idea of re-doing it. But that is way down my priority list so it may be a while. My son showed me a trick that works reasonably well and that is to freeze the batteries for a day or two. We took a cordless phone battery that would only last 5 minutes and cost $30 something to replace. We froze the battery and it would hold a charge for a half hour conversation for another 6 months after that. I froze the PC battery once, maybe I should try it again. I haven't really needed it lately.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.