I have been looking into rebuilding the NiMH battery (call me a Luddite). It is challenging because of the way the battery modules are assembled. There is no room for any kind of mechanical connector, so you have to weld tabs between each cell. E+ used very thick tabs, presumably because with all the cells wired in series, the full current has to go through each tab. I have not been able to find an affordable welder rated to weld through .5mm nickel, although there is one available as a kit that comes close. I have inquired at a few custom battery companies, but none were interested in taking it on. One referred me to Batteries Plus, which is a franchise operation. I couldn't get an answer at all from the store closest to me. They are supposed to have welders in their stores, but I doubt that they would have one that would be adequate. So, even though the cells themselves are still available, it looks like a dead end.