On Tuesday, 13 September 2016 11:14:42 UTC+1, George wrote:
Hello everyone,

I am in the process of resurrecting a lot of lead acid Cells that I washed out, dried and sealed in the 1980's I shipped about 100 back to UK from the Oil Company in the United Arab Emirates. Some time ago I heard about using Alum, - Aluminium Sulfate as the electrolyte and I got about 30 - 40 cells working, OK.

As I do not need them at the moment I emptied them again and cleaned them out with rain water and some I actually removed from the plastic containers to clean out the sediment that I thought must have stopped a few of them from working. When I got them apart I discovered that some of the positive plates had broken off where they were all connected together and where the fat lead terminal went up to the top of the case. They had all fractured at the same place, although the rest of the plates including the negative ones seemed in very good condition. Only about 6 or 7 have fractured like this and I do not know why. The other question is how do I repair them. I can easily get at the fracture and I have filed the faces back to solid lead but I wonder what is the best way to repair them, providing a low resistance joint again.

Is it possible that solder, being a tin / lead mix will have a lower melting point than pure lead? If so, it will be fairly straight forward. the other way might be to drill small holes and clamp the pieces together with stainless nuts and bolts. The electrolyte is probably not going to effect the materials. Has anyone any thoughts about this before I start to experiment. I am going to make up a bank of cells to feed an inverter to provide a no break supply for a house. or to charge up during the day from my solar array, (4Kw)

Any comments will be welcome. Thanks George.

You need a high tin solder.
This reduces the melting point to below lead.
And a large soldering iron.