Making connections for a 1P string should be easy, even doubling up on a 2P group would still be easy. My plan is to use a soft copper foil between the aluminum tabs to help ensure a good physical connection (Al-to-Al would still be fine). It might be unnecessary, but copper foil is cheap and I already have some. The outer clamping pieces will be thin steel bar. I'll try to post a pic this weekend. (similar to what Inwo posted above in the 6S potted battery)
All tabs will be covered at first. I won't be using sticky tape, because I don't want any glue-residue. I will only uncover each pairing of tabs as needed. After clamping together, they will be covered again before uncovering the next set. I only mention this because I don't think the welding system is a requirement. I am certain that the welding works well, but I am also just as certain clamped tabs work fine. The welder would be faster if you are building 20 packs or more, but I am only building one, or maybe three...
These might be able to start a 4-cylinder car by themselves, but as an experiment, I bought 15V worth of super-capacitors. I am still learning, but I have seen these SC's on youtube starting a car. Without an additional battery attached, they turned over a car for 30 seconds (when spark and fuel was disabled), plus they are compact and light.
I want a 12V battery that is easily portable for charging a cell-phone and laptop in an emergency (I already have a 12V solar panel in the closet), 12V outlet socket, and also several 5V USB ports. I hadn't thought about adding the car-starting ability until I saw the high-amps these were capable of, plus I stumbled across the super-capcitor videos. They seem a perfect match for LTO, since both should last decades.
I was also researching 4S LiFePO4 as a 12V pack, but I bought the LTOs as a fun experiment...If the SC's work as well as I hope they do, then I don't need high-amp batteries, and I will put the LTO's in a separate case for my son.
Cases are easy and affordable, thick plastic "field boxes" are available in a variety of sizes (they used to be called "ammo boxes"). Harbor Freight Tools (HFT) has heavy-duty suitcases in 3 sizes under the "Apache" brand.
https://www.walmart.com/ip/Plano-Sports ... n/23247620