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  1. #1

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    Which Unit Do I Choose?

    Hello,

    I am looking for advice on which unit I should choose for my 33% Week's Special it is powered by a BME76cc twin and 5 8411s plane + a couple of standard bb servos. It has been flying fine for several years on single nicad but its time to upgrade. I would like to use A123s unregulated for battery power so I would like a unit that has no regulator.

    I'm a bit confused about the different options.

    I'm also putting together a 50cc Ultimate and I would also like a unit for that that contains the optical kill. Is the PowerExpander Sport Plus capable of supporting A123s?

    Thanks for your help in advance.

    Robert

  2. #2

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    RE: Which Unit Do I Choose?

    Hi Robert,
    I think the best unit for both planes would be the PowerExpander Sport Plus. It was designed for 5S NiCd/NiMH and 2S A123 batteries. Let me know if you have any more questions.
    Robert Ritchey
    Owner, Smart-Fly
    www.Smart-Fly.com

  3. #3

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    RE: Which Unit Do I Choose?

    Thanks Robert,

    PowerExpander Sport Plus it is! Anyway am I right in assuming that any of the PowerExpander line is good for unregulated A123s or must you use a regulator with these?


    Robert

  4. #4

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    RE: Which Unit Do I Choose?

    Hi Robert,
    Most people do not use a regulator with the A123 batteries. The PowerExpander Sport Plus has a "BatShare" built into it so there will be a 0.4V drop between the battery voltage and the servo outputs due to the diodes. Most people think this is a good thing as it means your servos will see voltages between 6.8V (7.2V battery voltage) and 6.2V (6.6V battery voltage, the plateau of dischage). Of course, as will all our PowerExpanders and PowerSystems, the receiver will see a constant 5.0V due to its dedicated regulator. Let me know if you have any other questions.
    Robert Ritchey
    Owner, Smart-Fly
    www.Smart-Fly.com

  5. #5

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    RE: Which Unit Do I Choose?

    Robert,

    I'm not trying to monotonous but here is what I am thinking. 1 2300 A123 pack connected to a Fromeco Kodiak switch. From the Kodiak two connections to the PowerExpander Sport Plus using whatever connector is required for the PESP from the single Deans output of the switch. Will there be an issue with this due to the BattShare? Am I all wet? Is there a better configuration that I should be looking at?

    Sorry to be such a pest but I'm looking for a simple yet elegant solution that doesn't require 4 batteries to charge and maintain before I can fly. I'm looking for a day where I can fly and not worry about potential brown outs in both the receiver and the back of my pants.

    Thanks again,

    Robert

  6. #6

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    RE: Which Unit Do I Choose?

    Hi Robert,
    I really, really suggest you use two batteries for the flight pack and one for the ignition. Having two batteries on your flight pack is the cheapest, most effective redundancy you can have. You should get the Kodiak switch with a JR output. I think you will need two Kodiak switches. The BatShare does not factor into this really. Let me know if you have any other questions.
    Robert Ritchey
    Owner, Smart-Fly
    www.Smart-Fly.com

  7. #7

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    RE: Which Unit Do I Choose?

    Robert,

    Yeah that puts me at 4 batteries.

    2 RX
    1 IGN
    1 Slimeline Showtime

    Really wish someone would come up with a way to connect the smoke pump into the RX battery reliably. No worry of power drain just for those of us that have been flying giant scale long before the likes of ready made power systems existed knew this to be additional stress on the power bus that could potentially drop voltage way too low due to the cheesy RX connections and crappy discharge rates of the batteries. Anyway can the showtime be wired into the PowerExpander Sport Plus somehow or just tapped off the switch like a Seiko? These pumps claim to draw only 250mAh.

    Thanks again Robert I know that you must have this discussion over and over again but the models that I am trying to outfit are not huge and weight penalty is an issue. Even though the Weeks is 33% it really is more like the average 50cc bird. The real Weeks Special was like a cut down Pitts that had oversize controls and serious beef up front. Needless to say the 76 drags it vertically like a rag doll and I'm fighting to keep it in the 18-19 pound range.

    Based upon your advice I am thinking 2x1100 A123's for RX and would like the Showtime powered off of this and 1x1100 A123 for the IGN. I'd power the Showtime off the ignition but really don't want the feedback since I use PCM. I have way too much invested in PCM to make a change anytime soon. Any ideas? Sorry for the dumb questions.

    Robert


  8. #8

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    RE: Which Unit Do I Choose?

    Hi Robert,
    Why can't you use a servo output to power the smoke pump? I have had several people do this. Maybe I am missing something?
    Robert Ritchey
    Owner, Smart-Fly
    www.Smart-Fly.com

  9. #9

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    RE: Which Unit Do I Choose?

    Robert,

    The Showtime, Skywriter, and many others use a separate power tap that is intended to be connected to a separate battery to reduce load on the receiver power bus. This allows for up to 12v to be used when you have really large engines that are capable of potting that much fluid. I use these because they are easy to adjust, self priming, allow me to mix with the throttle to ensure I don't get doused, and are extremely reliable. I don't need 12v but only around 6v to power the pump which would be perfect if I can get this power from the dual battery setup. Can this power tap be plugged into the PESP somewhere?

    Robert

  10. #10

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    RE: Which Unit Do I Choose?

    Hi Robert,
    If you are using the PowerExpander Sport Plus you could plug the smoke pump into an unused servo output on the unit. That way its drawing power from the two batteries at what ever their voltage is minus 0.4V. I guess I am missing what you are asking because this is what I suggested in the previous post. You have eight channels, each with two servo outputs. You can draw power for the smoke pump from one of the unused ports. It really might be easier if you called me.
    Robert Ritchey
    Owner, Smart-Fly
    www.Smart-Fly.com

  11. #11

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    RE: Which Unit Do I Choose?

    Robert,

    Now I get it. Sometimes I overthink things. I thought you were referring to those folks that use smoke pumps like the original Don Harris and a host of others that use only one tap that plugs into the receiver. These were designed to draw power only from the servo output on the receiver.

    Thanks again for your help, patience, and newfound education you've gone way above and beyond on the customer service front. I got it all figured out now so I'm off to place my order.

    Robert


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