NiMH for both. The First-gen Insight has 120 cells for 144V nominal, 6500mAh. Large battery arrays are very complex, and a number of issues can develop with them, and many of those issues can be rectified by the DIY'er. What exactly are you trying to do, and do you own any Hybrid battery packs?
A good resource for general background information is
Nickel-metal hydride battery - Wikipedia, the free encyclopedia .