lipo questions...

[BrianG]

IMO, it somewhat depends on what 5s Lipo and what 16 cell NiMH packs you are comparing. Some packs hold a higher voltage under load than others. Generally, lipos with higher capacities and C ratings will hold the voltage higher under load. Of course, the packaging gets bigger because you are paralleling cells to get that capacity. Each parallel cell is taking only part of the full load. However, popular opinion seems to hold that higher capacity NiMH cells don't quite have the deep deep discharge capability. This is probably due to the fact that the manufacturers are squeezing more capacity in the same physical size (or very close to it) sub-C cell. Something has to give when you do that, even counting technological advancements.

Ideally, a 5s pack is at 18.5v assuming a 3.7v nominal voltage per cell. 16 NiMH cells will be at 19.2v assuming a 1.2v nominal voltage. Lets say you draw 100A. If the Lipo packs is an 8Ah pack rated for 20c (160A), it will probably hold a higher voltage than a NiMH pack at that current since the NiMH will be closer to its max ratings. If that lipo pack drops to 3.5v/cell at 100A, the pack voltage will be 17.5v. If each NiMH cell drops to 1v/cell at 100A, the pack will only be at 16v.