I know that they're in Australia, The dendrites could have grown half a year ago, and the internal short could have "started" due to vibration or heat. But when there are no temperatures below or near 0°C ever, this falls out as a possibility.
When I watched the video, the first thing that came to my mind was it probably was an internal short. As @Korishan suggested I think it may have been dendrite growth, maybe due to charging at below 0°C?
If you want a spellchecker which also corrects grammar issues, then LanguageTool.org is a great tool. I use it all the time, and it's also available as addon for Firefox, chrome and I think also for opera.
You missed some important point... I'm going to build an ACTIVE balancer, that means the surplus energy isn't burned, instead it is transferred to the packs with less energy. So the only heat generated is the loss!
I think you don't understand what I mean.
It's better to do mixed packs (4sXp with both 2000mAh and 1500mAh), or you make two whole strings (4sXp with 2000mAh and 4sXp 1500mAh) and connect them in parallel (also each connection in between has to be paralleled).
Hope you understand now what I...