Sorry, I won't include build instructions, schematics, BOMs. It is a huge work, and I see no reason to do it. I will highlight some featrues, nevertheless.
The project has completely custom electronics - no arduinos, no off-the-shelf power supplies. Pure hardcore, components plus PCBs I made myself, circuits designed by myself, transformers calculated in my own spreadsheet, and hand-wound. There isn't any real purpose behind using no pre-built stuff, I just enjoyed doing it.
PCBs were routed using TopoR. It generates cool vintage-like layouts like this:
And here is a pic of the first charging.
So that's it. I don't think I have a pic where I got the clock part of the thing working =)
And now, whenever I get a new battery, I run it through a charge-discharge-charge cycle, and then plot a picture like this: