I use to race R/C cars for many years. One thing that was important to get the most from a pack of batteries was to get packs of batteries that were matched. They would use machine to put a load on the batteries and count the time it takes them to discharge under a certin load. Each cell would then get a tag and those that were similar in capacity would be grouped together. This would make the pack good or better then just grabbing the cells and grouping them randomly.
They claim that during production some cells are made with a better or worse batch of chemicals, some are filled more then others so this gives them more capacity. Has anyone done this with their batteries? matched them? It would be cool to get a few packs that are close to the same voltage and capacity.