Join Date: Jan 2007
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Correct...you need some kind of rosin to allow the solder to stick properly. In a previous life I used to be in the battery business (motive power, i.e. forklift). I delt with high current DC battery and charger repair and made all of my own cables for batteries and chargers. I used to use 100% lead and rosin paste. I think the point being made was don't use the stuff with the rosin built into the solder. There's not enough rosin when doing stranded wire. Ace Hardware used to sell 100% pure lead sticks, but for what you are doing, the lead/tin combo stuff will work fine. Do not crimp high currect DC connections, especially when dealing with batteries. The exposed copper in crimped connections usually corrode faster. This is a big factor with forklift batteries, because of the heavy gassing, vented caps and high currents. Automotive applications are not as bad because the batteries are pretty much always fully charged and don't gas as much, but I always prefer soldered over crimped anyway.
Also, use propane, mapp, oxy/propane or oxy/NG for gas. Do not use oxy/acetylene, it will contaminate the lead. As far as cable, I used to use 600V welding cable. It's oil/gas/chem resistant, very flexible and available in sizes from pretty much #2 to 4/0 in red or black, although most electrical supply houses only have black. I would use black and red electrical tape to seal up the connection...shrink wrap works too, and is a little better. The best stuff is the shrink wrap with the gel inside that melts and makes it watertight, but it's not necessary.