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  1. #1

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    How do I convert my Nitro NiCad Rx battery to LiPo

    I fly both nitro and electric. On my Nitro I use NiCads on my electric's I use LiPo's. So how do I convert to use only LiPo's on my Nitro planes? Do I need some sort of voltage regulator to cut down to 6v or 4.8v?

    I've heard that I need to buy a 2S lipo not sure of the miliamps? How can I determine the size of the battery needed? For example I'm building a 60 size P-47 Warbird it has 8 standard size servo's and one hight torque retract servo. How would I detertime what size lipo to get?

    I use Spectrum recivers typically AR500, AR6200 and AR7000.

    My LHS is out of them at the moment and they didnt have a whole lot of info on them.

  2. #2
    hugger-4641's Avatar
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    RE: How do I convert my Nitro NiCad Rx battery to LiPo

    Check back in periodically and someone will probably have a more precise answer. The milliamps are going to determine how long you can fly. Off the top of my head I would say you need at least a 2000mah pack. But to be sure you would have to determine exactly how much current all those servos and your Rx are going to pull and multiply by how long you want to be able fly between charges. As far as reducing the voltage, you will need a regulator or a bec of some sort. Or, if you are really cheap like me and don't mind taking the risk, you could figure out your load and resistance needed and just put a 10cent resistor in a jumper lead to connect the battery and rx, in this case a two cell lipo would definitely be better. The voltage is more important than the milliamps. A 2cell lipo is 7.4 volts (actually about 8.5volts when fully charged) so its a lot closer to the 5 to 6volts that you need for your Rx and servos than a 3cell (11.1volts). I would recommend the BEC/regulator as the safest option and it will allow you to try different batteries and still put out the same current to your rx. Here's a link to one that would probably work, but I've not personnally used it.

    [link]http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=3735&Product_Name=HXT_UBEC_5/6v_output,_5.5~23v_Input[/link]
    Jerry
    AMA -922698 Nomal people scare me, but not as much as I scare them...

  3. #3
    hugger-4641's Avatar
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    RE: How do I convert my Nitro NiCad Rx battery to LiPo

    Here's another option if you think you might want an onboard glow driver some day.

    [link]http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6696&Product_Name=iMAX_iBEC_6A_Linear_Regulator_&_Glow_Drv.[/link]
    Jerry
    AMA -922698 Nomal people scare me, but not as much as I scare them...

  4. #4
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    RE: How do I convert my Nitro NiCad Rx battery to LiPo

    Ive converted my planes to LIPO. I use a CC regulator and a 2 cell 1350mh for the small planes and 2000mh on the larger ones The CC reg can be set with a lap top. I have mine at 5.5V

    http://www.castlecreations.com/products/ccbec.html

  5. #5
    DGrant's Avatar
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    RE: How do I convert my Nitro NiCad Rx battery to LiPo

    I have a question... as I'm just reading here.. Why the need for a 2000mh pack.. I'm seeing its 7.4v @ 2000mh .. The original poster has 8-standard servos, 1 high-torque retract.. is there an equation that applies to this? Is there an average amp draw(which might depend on the servo and linkages).. but roughly with simple smooth linkage, and nothing overworked ? How long will the power last in minutes? Or maybe.. how much current will the system draw in average use? How relative is it to Lipo's powering motors? Very curious.. Thx.

  6. #6
    goliathman's Avatar
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    RE: How do I convert my Nitro NiCad Rx battery to LiPo

    its all about the servo not about formulas. Most cheap servos twich at 6V good ones dont, and soon all good servos will be designed for 7.2V nominal. The capacity of the lipo will depend on the amont of head room you want for your flight time and servo draw. Use a 1350 make a 20min flight and see how much you have left in the lipo. depending on how often you want to recharge durring a flight day you can use a larger battery.

  7. #7
    DGrant's Avatar
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    RE: How do I convert my Nitro NiCad Rx battery to LiPo


    ORIGINAL: goliathman

    its all about the servo not about formulas. Most cheap servos twich at 6V good ones dont, and soon all good servos will be designed for 7.2V nominal. The capacity of the lipo will depend on the amont of head room you want for your flight time and servo draw. Use a 1350 make a 20min flight and see how much you have left in the lipo. depending on how often you want to recharge durring a flight day you can use a larger battery.
    Some not so cheap servos chatter at 6v too. I've been under the impression that each servo has an average current draw, that can be multiplied by the amount of servos, in which case would give an estimated usage based on consumption. The servo chatter can be held at bay decently with a regulator.. but the overall draw is what I'm concerned about.
    I think a 2000mh lipo weighs about what a 1500nicad.. but is the same usable power.. ? Maybe? With the Lipo being at a higher voltage of 7.4v, there's an obvious "push" of voltage thereby using more power.. at a higher voltage....
    Is this the advantage of using a lipo in the whole scenario? ,,, and what about lith-ion batteries... do you know of any advantage there??
    I really should research this(I guess that's what I'm doin now..hehe).. thanks for the info..

  8. #8
    hugger-4641's Avatar
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    RE: How do I convert my Nitro NiCad Rx battery to LiPo

    Among other things, one basic advantage of the Lipo is power vs weight. A lipo pack that puts out the same current for a comparable amount of time will weigh less than a nicad or nimh. Some reasons for this are the construction and the cell voltage. A Lipo cell is rated at about 3.7 volts per cell and actually puts out 4.2 volts when fully charged vs a nicad cell at about 1.5 volts per cell. A 3 cell lipo is rated at 11.1 volts, to get this voltage from a nicad or nimh it would have to be 8 or 9 cells.
    Jerry
    AMA -922698 Nomal people scare me, but not as much as I scare them...


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