Battery Questions
 

I have an E-Maxx w/ a 8XL and 9920 geared 22/66. Runs great on 16 cells without getting hot (Throttle EPA set at 80-85%). The problem is my runtime. My GP 3700's loose considerable power after 7-8 mins at the track and I need a 10 min run for the A-Main race. The batts are 9 months old and were run and cycled regularly. Could my batts have bad or gone flat?

No, the runtime is about normal. You can increase your runtimes with lipo, or change your gearing a tad. Changing your gearing won't do as much though. you could also increase your mah

What Neweuser said, and maybe going to a 9XL, or even a 10XL, or a more efficient motor altogether (LMT/Neu). The higher turns count will pull less current and increase runtime. I run 14 x GP3300 unmatched cells and 10XL on a Revo (9.75lbs loaded, total gear ratio ~16:1) and I get about 15 minutes. I'm not running quite as hard as a good driver in a real race would, but pretty close.

16 cells on an 8XL is a little on the higher side of 40k rpm, which is where efficiency starts to fall.

Actually, I am turning 36K rpms at the loaded value. How would the MaxAmps 5s2p 3000mah(2s2p and 3s2p) work with my 9920/8xl setup? Would the motor draw too many amps for the controller?

You need more like a 4 or 6000mah setup.

Try 20/66 gearing. That should help with the run time and still have good speed and a ton of torque.

At 20/66 my motor runs hot. Squee, I meant 6000 mah. Would the 6000 mah MaxAmps lipos be OK on my 9920/ 8xl setup? Not in the mood to buy another controller as I am also running a brushless CRT and brushless Hyper 7.

Yea, those should be ok. I see what you meant, now. 2S2P made of 3000 mah cells.

I run a feigao 8xl 9920 ubec 20/66 on 14 cells with no heat issues.Runs pretty descent on 12 cells too

I would use a 4S2P 4000 setup of maxamps. The runtime will be great, with a very nice punch. You only need a LVC (low voltage cutoff) the nicest one i could find, for a cool price, is the liposhield from dimensionengineering.

http://www.dimensionengineering.com/LipoShield.htm

Serum, thanks for the lead on the LVC. Now for chargers. I have a SuperBrain 977 that will charge up to a 3s lipo so I need a cell balancer. Or would I be better off purchasing a new charger? I would like to be able to charge at least 2 packs at a time.

If you want to charge all the cells at once, you are better off buying a new charger i think? (depending on your personal state of mind in terms of patience)

I did not mention that my 977 can charge 2 batts a 5 amps each. Which chargers and balancers work well on lipos?

I would recommend one of the E-Stations chargers with a E-Station PB6 balancer.

Has anyone tried the "e-Station BC-5 Balancing Nicad/NIMH, Lipoly Charger"? It has a balancer built in and monitors the cells individually.