When I was out with bike.1 yesterday, the battery powering the ammeter/voltmeter stopped working.
After using it for a while, I've realised that I don't really need the ammeter; all that tells me is how much power I'm getting from the bike, and I pretty much know that already. But the voltmeter, that tells me the state of charge of the battery, and that's useful.
Also - each time I took the battery pannier off the bike, I had to unplug two leads - the battery power lead, and the ammeter/voltmeter lead.
So I've replaced the ammeter/voltmeter with just a voltmeter. That doesn't need any power, it just runs off the battery. And that means I don't need the second lead, so in future when I remove the battery pannier, I'll only have to unplug one lead.
I'm planning to go out tomorrow to complete the circuit that I did half of yesterday. The weather forecast is for a bit of rain in the morning, but soon clearing up.