Today, I started off near Biggin Hill (home of the RAF until 1992), a ring of 17 caches some of which were quite difficult, but with some persistence I got them all. I did that ring on foot, because it looked like it wouldn't be bike-friendly, and after walking round, I think I was right.
Then on to Westerham for a ring of 20 caches, and nearly all of them were difficult, so I was pretty pleased to get 18 of them. I did those on the bike, using battery 6, but it was only a few kilometers.
That took up the whole day's caching - difficult caches are more time consuming. But they're also more satisfying when you get them. And more frustrating when you don't.
I also phoned my bike battery supplier, and he said it would be OK to open up the battery, I wouldn't invalidate the warranty. So I did, and the problem was very simple - a cold-solder joint from the power to the fuse. So I resoldered it properly, and now the batttery works fine. That's saved the courier costs up to Scotland and back, and probably several days.
One of the drives on my Ten Terabyte Tower was misbehaving. SMART said that it had 1800 reallocated sectors, which is a lot, so I took it out and replaced it, and the new drive is fine. I noticed that I'd put a label on that drive - it had failed in another system, and I'd reformatted it. Obviously not a good idea. That drive will probably turn up in a cache some time, I won't be using it again.