acdii

Iam building a P-51 with possible gas engine. The servos I am looking to use can use 6V power, and there will be 6-8 servos, possible S3004 Futabas, and a Spektrum RX. If I use a 2S Lipo, what C and mah size would I need and what would I need to go between the pack and the RX. If I go gas, the ignition needs power too, so would I use a separate pack, or share one pack?

HunkaJunk

If you use a 2S LiPo the voltage would be too high (7.4 volts) an you'll have to use a voltage regulator.

Ihave been using 2S LiFe batteries (A123, Lithium Iron Phosphate), the voltage is 6.6 volts, I power RX's right through the switch with no regulator. For Spark ignition modules I have been using the Wike RC battery eliminator filter, which allows me to power the ignition module from the same battery pack, and is filtered for RFI.. I love these things, they work great!

acdii

So something like this? http://www3.towerhobbies.com/cgi-bin...?&I=LXYAS9&P=0
Three output leads, and a balance jack. SO one of these can be used, one jack into the RX, one for the ignition, and the third as the charging jack? My TT Charger supports all battery types and charges my Lipo with a DEANS like this one has. It's a 2100 10C, how many flights could I expect between charges when used for both?

BuschBarber

My Feedback: (2)

The C rating determines how many amps you can draw from the battery pack. A 2500mah (2.5a) 1C pack will allow you to draw 2.5a for an hour, 5a for 30min, 10a for 15min, etc.. A 10C 2500mah battery just means that you can draw a max of 25a continuously, however, you could only fly for 6 minutes before you would have to land and recharge. When you are talking receiver packs, it all depends upon how much current your servos draw during an average flight. The Capacity is a more important number than the C rating unless you are talking electric motor batteries.

A.T.

Do not consider using S3003 ot S3004 with any petrol engined model as they are very susceptible to vibration.
(Being the reason why the discontinued S148 and S3001 servos were re-introduced for use with small glow powered Heli etc.)
S148 & S3001 vs. S3003 & S3004 refers.
As an aside, there would be few models utilising a petrol engine which would be small/light enough
to ensure the gears on any of those servos would not strip in flight or hard landings.
Suggest you consider larger servos with thicker/stronger gears or MG servos.

Alan T.
Alan's Hobby, Model & RC FAQ Web Links

TimBle

a 2100mA.hr LiFeSource pack running both Ignition and Rx will give you around 5save flights if using 9std analogueservo's and a voltage drop diode between the battery and the ignition.

I'd up the capacity to 3000mA.hr if using digital servo's

acdii

Thanks. Ithink Inarrowed it down to 6 analog servos, one retract servo and a pair of Eflite electric retracts. Ithink I will go with a separate pack for the ignition just to be on the safe side.

BarracudaHockey

My Feedback: (11)

You certainly could, but I run 50CC planes with a lot of servos (no retracts) with a single A123 with drop down.

I'd go with a 2300 rx A123 and an 1100mah A123 or 4 cell nicad for the ignition if you're going to split battery duties.

I get mine from WrongWayRC.com

vertical grimmace

My Feedback: (1)

I would not recommend the Eflite retracts if you are using an engine. The little switches on the circuit board get destroyed by the vibration of the engine. A small lobe of the gear mechanism is in contact with the switch at all times and My gas engine destroyed the switch within 3 flights.

Just a heads up. I think they are really designed for electric, low vibration situations.