[redshift]

Was looking at the link for your packs, seems Tower has put out some bad info.

"NEVER allow to Discharge below 2.5V per cell"

NO. The absolute minimum is 2.8V, and the widely used cutoff is 3.0, for a buffer zone.

Many people (myself included) use 3.2V per cell for cutoff, usually anything below that you will notice the power drop off.

I am using Hyperion Swift Classic 4000 2S 20C packs, which are very similar to the first set of Orions you linked. You'll get 15-18 minutes in a proper setup. Maybe use that for reference until you get a feel for things. The 3800 hardcase packs will be good for 12-15 probably, but will be stronger.

You can charge the 4000's and the 3800's at 4 amps for a 1C charge rate, technically you would charge the 3800's at 3.8 amps, but 4 is close enough. And just so you know I have been charging my Hyperions at 8 amps (2C) for about 9 months now, they take it just fine. Incredibly good packs, nothing but praise for 'em!