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Power boards/expanders really needed?

Discussion in 'Onboard Electronics' started by capthis, Jul 18, 2016.

   
  1. capthis

    capthis 70cc twin V2

    I've flown Giant scale for a while now with a little bit of a break for a few years. When I flew before the biggest planes I had were 35% 100cc. Back then we used dual 6V NIMH packs, on the Rx and a 4.8 on the ignition each with their own switch.

    Since getting back in a few years ago I have flown a few 35% airplanes with (2) Life 6.6 packs each with their own switch into a separate port in the Spektrum Rx. I have also started using a opto kill now with either power coming from the Rx or from an extra lead (dual) from the battery.

    I have also flown 40% size planes the same way with my typical setup being 4 aileron servos total, 2 elevator servos total, 2 rudder servos total and a digital servo on the throttle.

    I've used a couple of the Smart-Fly boards and they are fine, but they add cost to the airframe. I don't run smoke, and I usually only fly about 5 times before recharging. I use primarily all Hitec digital servos, 5955, 7955, 7950, 7980 etc. I also check both switches every time before taking off, and am very careful when setting a new plane up that nothing binds, and nothing fights each other.

    Am I pushing my luck? The 35% planes have all been rock solid. I haven't flown a 40% setup this way much, but have done it. I don't fly high energy all the time, but do some, and 3D some, and fly Imac style some.

    Thoughts? Help educate me here if I am way out of line?? I know a stalled servo eats up power quickly, but I always try and check all my surfaces before each flight, and as I mentioned before I check that both batteries are powering the Rx each time before I take off.

    Thanks for any advice.
     
  2. jhelber08

    jhelber08 70cc twin V2

    I guess some of it depends on the radio you're using. I've only been flying for about 4 years now and with the exception of my first 100cc have used spektrum powersafe receivers. I only used the smart fly on the first plane because my radio wasn't capable of matching servos (and honestly I was clueless on mechanically setting up a plane and thought a smart fly was needed.) Shortly after my first 100cc well I had to have more and at that point it was cheaper to buy a DX18 than outfitting all planes with smart flys.

    The only issue I had with this setup was that as my flying got aggressive I found that LiFe/A123 batteries experienced quite a drastic drop in voltage during high energy maneuvers and migrated over to HV setups and Lipo RX batteries. I never had a brownout or lost control but I was showing voltage drops down to around 4V's in some instances.

    I've flown strictly HV servos (mks to be exact) and lipos with powersafe receivers for the past 2.5 years or so and couldn't have been happier. I recently switched from spektrum to Jeti which basically uses the same principle with their central boxes which handle the battery sharing. The switch was purely based on the fact that I'm nerdy and like the built in telemetry features of the Jeti, no separate modules for basic receiver info and the programming is also far more advanced on the Jeti in my opinion. Also the central box tells me how much current my servos are drawing and logs that during flight. The central box will also shut down a particular channel in the event of overcurrent and there's probably more features I'm not even aware of. So far I'm really digging that decision.

    So in short, no you don't need smart flys to have a good reliable setup. I would definitely still recommend running a setup that has 2 batteries though. I have been saved several times that I'm aware of and probably many many times that I'm not aware of by having a 2 battery setup.
     
  3. JAG

    JAG 70cc twin V2

    I like the power safe receivers since you have the batteries going directly to the receiver. No switches in between to fail. Switches can fail even after you check them, they can fail in the air. I also don't like the gauge wire that is used with most switches, its to small for my liking. With the power safe receivers you still have a switch, but if it were to fail, the receiver fails with power ON. So even if it comes unplugged or wires cut, the receiver stays on.

    But I'm a newbie, as you know so don't take my opinion to far.
     
  4. capthis

    capthis 70cc twin V2

    I'm running Spektrum Rx that are not power safe receivers just 9 and 10 channel.
     
  5. jhelber08

    jhelber08 70cc twin V2

    I've run that on 50cc stuff but still use 2 batteries in some sort of fashion to the rx, I'm sure that will work too...just preferred the power safe for simplicity.

    On my newer jeti setups, for my 2 50cc's I am using a plain jane 9 ch in one and 11 ch (came with the radio) in the other but still with 2 batteries in each. No issues so far.
     

  6. Get some powersafe Rx's, and forget all about power expanders and that other hooplah.....

    Buy the most channels you can.
     
  7. capthis

    capthis 70cc twin V2


    I don't really want to buy new rx for all my planes if I don't have too.
     
  8. If you are running dual Rx, don't worry about it. Otherwise, Spektrum Rx can handle 35A continously.
     
  9. capthis

    capthis 70cc twin V2

    Haven't run dual rx since the old 72mghz days.

    If a Spektrum rx can handle 35 amps what does each servo pull?
     
  10. If you run 8 servos, thats 4A continously, and you arent going to pull a consistant load. You will always have a spike.
     
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