While 4.8v (4 cell) packs can be used, a 6.0v ( 5 cell) pack provides more headroom over the 3.5v minimum operating voltage should the battery sag durring heavy load. The battery type is also critical as many buy just on capacity where in many cases these cells are good in low discharge application like transmitters but can fall flat on their face when used with high torque servos. The latest AA size NiMh batteries in the 2000-2500mah range come to mind so pick your packs wisely.

I do not recommend using the SPC port in a nitro/gas plane, only electric to prevent the BEC in the ESC from causing a brownout if it sags under load, plus allow the main pack to feed back it's voltage where we can set a custom low voltage warning and simply fly as hard as we want until the warning goes off instead of using a timer.

For nitro/gas it is always best to use a battery that is known to be able to handle the servos used (or use dual packs if needed) and then the telemetry will show exactly what is going on as it will log the lowest voltage realized durring the flight to know how well it is performing in the specific application. The first thing I do before I fly is look at this screen (simply tap the battery icon to get there) and wiggle all the sticks as quickly as possible as see what the lowest voltage drops to. This is one hige advantage to the battery telemetry being built in. Most people have no idea how low a battery can drop to under load.

Follow these guidlines and you will never ever have a brownout in any airplane!

Mike..