I picked up the bike. The lady told me it had only been out three times; after they bought them, they decided that the area was too hilly for biking. So I got a Haro DX folding bike for £56, almost new condition (I can see from the tires it's hardly been used), a real bargain.
It was raining on my way there, but that became a light drizzle just before I arrived.
Then onwards to do some caching, by which time the rain had pretty much stopped. This was almost entirely on roads. The new battery pack again performed wonderfully, and I did 43 caches, two DNFs.
I discovered something good by accident. I've always been careful not to reverse the polarity when connecting the old batteries to the controller - it's easy to plug it in the wrong way round (which is why I'm using kettle plugs on my new battery packs, you can't get those the wrong way round). So today, I made the inevitable mistake - I connected it the wrong way round. Worst case was there's a flash and a bang and a dead controller. Best case was, nothing happens. And nothing happened. So I saw my mistake, plugged it in the right way round, and everything worked. Nice.
My order from Hobbyking arrived today. Or rather, someone else's order arrived. Right delivery number, completely wrong contents. Sigh. So now we'll have to sort this out.