Thanks for the solder tip. Was not aware of this. Need to get back to the shop really and see what they have in this respect...

For the voltage variation I struggle to see how it relates to connections. I may be wrong of course but it seems to me that earth batteries simply don't have a steady output until they are in the ground. Too many variables on my kitchen table. Like I said, even noise would disturb the voltage.

By the way, I have been alerted over on hive that I am reading my multimeter wrong and in fact I am getting just one milliamp! So, I have more copper and will make more cells in parallel now to increase this.

Looking forward to getting this into the garden too, as I believe the output will increase once it is deep in the earth. Let's see...