A few things.
First of all, at some point yesterday, probably while heaving the bike over an obstacle, I managed to break the wires leading to the voltmeter. Not a big problem, it just means that I didn't have a measurement of the battery life remaining. Of course, the battery has its own way of letting me know that it's empty.
So I did some maintenance today, and since I was going to be fixing that, I decided to reorganise the way that the battery is carried.
The way it's supposed to work, is that there's a platform that sticks out behind the bike, clamped to the seat post, to carry the electronics and the battery. This is probably fine for normal cycling on roads, but I'm going on very bumpy ground cross-country (or at least, on bridleways, some of which are very chewed up by horses hooves). So the metal platform has gradually been sheering off, and I don't really want to wait until it actually breaks completely while I'm in the middle of nowhere.
I removed this rear platform, and I clamped the small controller box to the rear carrier. The power inputs to this, are soldered to a plug (obtained by sacrificing a male-female kettle plug extension cable). The other end of that cable, is soldered to a connector that plugs into the battery, and the battery goes into a pannier that hangs from the rear carrier. So when I want to take the battery off (for example, if I'm lifting the bike over an obstacle), all I need to do is unplug that kettle plug (more precisely, an IEC 60320-1 appliance coupler, connectors C13 and C14) and lift the pannier off the bike. I tested it, and it works fine.
Then the voltage display. I have two displays, one which is just red blobs, which gives me a very rough idea of when the battery is getting empty, and the other tells me the voltage, in volts. But that's hard to read in sunlight while bouncing along on the bike, so I mostly rely on the blobs, and it was the blobmeter that wasn't working, because the negative wire had pulled away very close to the casing. So I took it apart, soldered in a new negative wire, and now that works fine.
While I was doing this, I noticed that the rear carrier had fractured; one of the supports was no longer bracing it. It still feels fairly firm, and I've wound it with tape to help, but I've also ordered a replacement from Ebay; this time, in steel, which I'm hoping will stand up better to the terrible punishment it gets on the rough terrain (the previous one was "alloy", which I think means mostly aluminium, with maybe some silicon, copper or zinc added. This gives a metal that's lighter than steel, but not as strong. These carriers are rated to 25 kg, and I'm usually loading them with 5 or 10 ... and still they fracture. So, I'll try steel.
And at the same time, I ordered a small pannier, because when I'm going on a short route, I won't need to take the big pannier and all the other stuff (bike repair tools) that goes with it.
As I was putting the tools back into the pannier, I thought that the cardboard case that's supposed to protect the rubber cement, wasn't going to stop it from getting squashed. Also, the plastic box containing the patches and suchlike, was broken. I had a look around, and now I'm using a Raspberry Pi case (the kind that comes free with the Pi as packaging) to hold the rubber cement, patches, chalk, marker, emery and tire levers, all in that one fairly rigid box.