[MetalMan]

If you ran your two 9cell packs in parallel, you'd only get 10.8v, but 6600mah and twice the amp draw capability. The performance would be approximately half of what it is now.

Since you have two 5s Apache packs, you'd want to run them in parallel. This would give you 5s (18.5v) 7400mah, with a continuous discharge rating of 111amps, which means that these batteries certainely won't be the limiting factor in any powerful setup that you can put in an E-Maxx. For runtime I think you can expect about 30mins, depending on how you drive and what terrain you drive on.