From what I can tell, still educating myself, the big issue is the cells are not reproducible yet. This means each cell has to be individually balanced or is overcharges and becomes ruined and or overheats and hence the sharing circuitry which has to monitor and control each cell. You buy it ready made with drop in replacement units like Smart Batteries or roll your own which is a lot cheaper and in my case allows me a lot more flexibility on the shape as I plan to use an existing space beside the power panel and it's 2 inches short for an 8D size battery.
