lightly sanding the +ve and -ve of the cell, get a little soldering flux (plumbers flux will do if desperate), use a tip that is rather beefy, allow the iron to warm up, place bar on cell, clamp, apply heat, when you hear the flux sound like frying baking, apply solder.
If you don't have a big fat tip, get someone to do it for you. I would offer, but it is a tad far for you to come for me to solder them up.
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