Lipo vs. Life(A123)

[othello]

A123 cells are a good choice for bashers.
. With the right charger(s) you will only need 2 battery packs to run all day long, as you can recharge them with 10A -> around 15 min for a charge with a 1p battery pack with 2200mAh.
. LVC is not a must as they drop in voltage abruptly when they are empty. You'll stop immediately to drive as power decreases rapidly.
. Powerwise 8 cells are more then enough for a truggy. I do calculate with peaks of 250W per cell (eagletree data with peaks of 2.5KW+ with 10s1p A123).

7s2p will rev the XL8 (2084kv) up to 44000rpm (3V per A123 cell under lighter load). With a 13t pinion your overall gearing is 1:15,775. With typical truggy tires (145mm) your speed will already be at 45mph+. Your Feigao would run way too hot and smaller pinions are not ideal.

6s2p A123 will rev the XL8 (2084kv) up to 38000rpm. Still a bit on the high side. With a 13t pinion your speed will be around 40mph. Already too fast for a small pinion for my liking.

5s2p A123 would be my choice (with a 2p setup) and will rev the XL8 up to around 31500rpm (this is slightly below what you can expect from a typical nitro engine under load in a truggy). With a 13t pinion your CRT will be at 35mph with plenty of pinion options to cover 35-50mph. A 14-15t pinion would be the perfect choice to reach 38mph (about what you can expect from a nitro truggy), a good speed for a track and the load for your motor should be alright to keep temps in check even on a hotter day.

If you would stay with a 5s2p setup (10 cells, around 750-800gr) you will only need 1 dewalt (ebay->DC9360) pack which contains exactly 10 cells.

I did run 10s1p A123 in a truggy and now do run 9s1p with a 1100kv Neu 1515/2Y. Runtime is between 8-9 minutes with a gearing for 38mph (62km/h) on a bigger track. A good friend of mine did run his Mugen MBX5T truggy with 6s2p A123, Neu 1515/1Y (2200kv) and a gearing for 42mph (68km/h). During hotter summerdays (86°F+) his motor got quite hot (up to 176°F). He was already using a small 13t pinion and didn't wanted to use a smaller pinion. He therefore switched to a HV setup with 11s1p A123, Neu 1515/2Y. Motor temperatures dropped somewhat between 150-160°F. Runtime also about 8 minutes as he is geared for higher speed and does run a heavier truck (thus consuming more energy).

Eventhough he is geared for higher speeds we do run head to head. Eventhough he runs 2 cells more (= more energy on board) then i do, his runtime is slightly shorter then mine as he uses more energy to push his 1lb heavier truggy to similar or higher speeds.