Receiver/Servo battery-or BEC -what size?

[marke]

can you tell me what is the best size without going to large for the 700 ?

thank you

[Corvette & Copter Guy]

This is what I use http://www.helidirect.com/plurx-2550...es-p-26537.hdx

[rcmarty]

Your not going to find a huge difference in weight as compared to the overall weight of the machine.

My thoughts are :

BEC off mainpack is going to be the lightest unless you prefer some kind of backup source ( lipo guard )

A dedicated rx lipo would add a touch more weight.

I'd think the best lightest combo would be the kosmic with a small 2s lipo backup ( eg 130x pack ) , but your going to pay for that few ounces.

Then one needs to consider how much weight were talking here , how much would a rx lipo add to the airframe ? 1% ? .5% ? or less.

Myself I run a 2s2p 4000 mah 16c pack. I made up this with some old TP thin stick style packs. I prefer this as it is a 2p setup and should one cell go bad the other in parallel will maintain the 8 volts


The BEC vs rx lipo is more of a personal choice these days. 2 schools of though on this.

- BEC -> can't forget to charge rx pack , lighter overall weight , extra electronic failure point, brown out risk

- RX lipo -> heavier , no electronic failure point , no brownout risk

I used to love the BEC and flew nothing else , but that was 600 sized and under. Now at 700 and over I've reconsidered the possibilities of brown out failure , electronic failure , crash costs , unsoldering mainpack wiring ( done it twice ). In the end I decided for the extra rx pack to babysit. At 4000 mah even if I forget to charge the pack and fly the whole weekend , I've got such a large capacity in reserve I'm safe.
I also keep full flight records and re-charge after 6-8 flights (800-1200mah) , also keep track of my average mah consumed per flight. ( about 300 )


Martin

[marke]

thank you for the responses- i went with a 3600 mah Pulse pack-good to 21 amp draw and it fits very nice in the back of the frame-- i feel better with the receiver pack vs the BEC-i will also supply 2 leads to the receiver for redundancy.

thanks again

[sl4ppy]

3600mAH? wow..

I use a 1300mah on my 14s 700 and that gets me 5-7 flights per charge for only 80ish grams.. I have 3 i just swap out that gets me more flights than I can generally fit in a day...

http://www.hobbypartz.com/98p-20c-1300-2s1p-2222.html

RX pack is definitely the better way to go. My 550sx' YGE with BEC incinerated the ESC, FBL (which was an SK720 with GPS; $1000 investment) and all 4 servos in a fairly mild crash a few weeks back. I'll never use a BEC again.

Here's the ESC and the circuit board of the FBL.

[Raptorapture]

sl4ppy, sorry to hear that. Which BEC was that? Did you find out cause of incineration. That really sucks!