Decided to try taking apart my battery charger, some kind of ancient and gigantic Japanese monstrosity which is way too big for its 20A max output, to see if I could find some burnt-out component or internal fuse or something to explain why it’s not charging anything. (The main fuse is fine.) The internet suggests a bad diode as the likely culprit. Here’s the charger:
However, it’s not very take-apartable. I got the front panel off but to really take it apart enough to get a good look at the electronics would require more patience and time than I have today. I asked the marina to borrow a charger for a few minutes just to confirm that it is in fact the charger having problems and it’s not some massive coincidence whereby none of my batteries, new or old, all full of water, are accepting a charge. Unfortunately there was a lot of bureaucracy involved and there were no chargers available right now anyway, so I gave up on that. I went in the marina’s chandlery to see if they had any chargers and they didn’t, so I gave up on addressing the battery charger problem for today and decided the solar panels would have to do for now.
But then the chandlery sent me an SMS that yes, in fact, they did have a 12V 8A charger for S$80. 8A isn’t really enough for long term use but it’s fine for now, and S$80 is pretty cheap. I figure it’ll be useful to have a backup charger anyway, even when I have a built-in one as part of the new electrical system; and this one is about 1/3 the size of my old one:
It works fine and is currently charging a couple of the new batteries: