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Thread: About Lumenier Batteries...

  1. #1
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    About Lumenier Batteries...

    I am curious why XT-60 connectors are the default connector for batteries purchased on getfpv.com instead of the larger XT-90.

    My quad currently has XT-60 connectors but it seems that since a quad has four large motors that means a lot of load on the power system. With four 30 amp ESCs wouldn't that add up to 120A which is a lot of current. No big deal for four 30A controllers and a 35C battery but it seems the weak link here is the connector.
    Add two more large motors on models such as the QAV540G and then there is all the current required to run all of your FPV and control gear. Are my numbers right.

    If I'm really drawing currents around 120amps to keep my QAV in the air it seems that it is more sensible to use a connector rated for 90amps instead of one designed for 60amps.

    So I've made this post mainly because I am curious not because I am critical.
    Last edited by timnilson; 16th February 2014 at 09:21 PM.

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    Even with 30amp esc's, most quad's won't pull anywhere near that. When choosing esc's, you have to allow for a tolerance, based on the amperage your motor will draw at max throttle. This is so that your esc's aren't being taxed 100% while they are on.

    In reality, good motors really don't draw that much power, so you still run 30amp esc's for the safety cushion (you could probably get away with 20), but they won't top out anywhere near 30amps each. If you maxxed out throttle on all four motors, you may hit the limit of an xt60, but as long as it's not prolonged, there's probably no harm in it. It's not like they just stop working instantly.

    Edit: One last note: Tim and a number of other vendors are totally dependant on their products (which they design and build) and their reputation. They wouldn't sell something that wasn't suitable for use with their primary products
    Last edited by pearlyred; 14th February 2014 at 01:56 AM.

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    Thank you for your reply. I know it works. I've had many flights on my QAV500 with the XT-60.
    I used eCalc xcopter and it gave me a maximum current of about 56amps which an XT-60 should handle. I don't know how accurate that website is. So do the motors only use 14amps? That seems low. Of course that's a good thing.

    I need to buy more batteries of course because this frame is so fun to fly. I have some 4S 5000mah lipos which are 30C and was thinking of going for a higher C rating for more speed. But it seems there would be no perceptible difference would there?

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    I'd still like to know other people's insights on this.
    Theoretically if a propeller snapped that would cause the motor to draw much more current correct?
    (Probably enough to burn out even a 30A ESC)

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    If the prop snapped, it would use less current since there is less torque on the motor. Run a motor without a prop, and you'll see it hardly used any power.

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    Lumenier.com timnilson's Avatar
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    Good question and all good points here. For a quad in the QAV family that's flown with recommended motors and props on the 10-11" size range, it's likely you won't ever hit 60Amps. But even if you did, the XT-60 would be fine. Now, even if you did see prolonged current above 60amps, the first issue you'd have is that the connector gets warm, then hot, and if you really overpowered it by a lot and for a long period of time, the XT-60 connector would melt and fail. If you felt it getting hot you know that's a bad thing as the current can't flow through the connector fast enough.

    An easy and non scientific test to do is to fly with your set up and feel the XT-60 connector afterwards. I would be surprised if it even got warm on your QAV.

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    Quote Originally Posted by joop1987 View Post
    If the prop snapped, it would use less current since there is less torque on the motor. Run a motor without a prop, and you'll see it hardly used any power.
    Oh yes of coarse. No load means nearly no current. So maybe my prop got stopped
    Last edited by popwebz; 14th February 2014 at 01:52 PM.

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    Hey mate,

    My current sensor shows my porky (2100g) QAV500 with High lift (APC 10") props just hitting 45A at full throttle after a dive.

    You've got heaps to play with on those XT60's.

  9. #9
    Underground - Cloud Bound Dust's Avatar
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    If your are running GIANT cell count batteries (6 cell and up), or flying something that needs a 100A+ ESC then I would put Xt90's on there. Till then, i really wouldnt worry about it. nothing added other than extra weight and less space.
    The 60 in XT60 is for 60a constant with prolly 70 or 80A peak.
    The 90 in XT90 is . . you guessed it! 90A constant prolly 120A peak.

    (fun fact the XT is from heX Tronic aka-hobbyking's main manufacturer)

    Also, Ecalc is a great starting place, but is not gospel.
    Last edited by Dust; 16th February 2014 at 09:27 PM.
    Live Slow - Fly FAST!

    FPV does NOT fly ASAP.

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    Quote Originally Posted by dalejw View Post
    Hey mate,

    My current sensor shows my porky (2100g) QAV500 with High lift (APC 10") props just hitting 45A at full throttle after a dive.

    You've got heaps to play with on those XT60's.
    Nice.
    Is that running a 3 cell or a 4 cell?

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