I use a123 cells as well. I run a 3p2s pack in my xxx-t pro truck & then I run a 2p 5s pack in a converted 1/8th scale. I get around 20 minutes of run time depending on the track. It is a perfect setup for running longer mains w/out putting too much weight in the buggy. I use velcro straps to keep the batteries in place so I can make a quick pit stop at the midpoint in the mains. Once I pit I can always have my pit man drop the pack on the charger and give me enough juice to endure anything that is left in a 45 minute main after I pit a 2nd time.