Re the discussion on making connections to battery cells: the summary
of the content so far is that soldering is dangerous, weldingis the
way to go, but is not trivial.

There's another possibility that I've seen read about but have no
experience with: conductive glue. From a commercial battery website I
saw (http://www.smallbattery.company.org....ire-glue.htm):

"Wire Glue - electrically conductive adhesive

Wire Glue utilizes the latest advances in microcarbon technology to
bring you a highly conductive glue at a fraction the price of
competitive products which use precious metals such as silver.

Wire Glue allows you to make low voltage AC and DC electrical
connections without soldering or heating.

There is no requirement to measure out and mix hardeners. Simply stir
and apply the glue to your surface and let it cure overnight. By
morning, you will have a reliable, permanent and electrically
conductive bond!

Cost-effective replacement for silver-loaded epoxies.

This lead free formulation is ideal for bonding all types of low
voltage electrical connections.

Wire Glue is not intended for high voltage or high current
applications. In high power circuits Wire Glue may become hot and give
off burning smells."

From another page on the same site:

"Can you make the tabbed cell I require?

We do not add tabs to order... Order a bare, untagged cell from us and
then carefully remove the existing tags from your dead cell. Apply the
Wire Glue to your cell's surface and to the tag, pop them together and
let it all cure overnight. By the morning your problems will be
solved."

This also suggests that you should be able to get similar but more
expensive silver-based glue. What current either will handle sensibly
I don't know - a data sheet would help.

HTH