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  1. #1

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    Need some help: Fully custom build was fine, now having throttle range issues

    I have a Savage .21 that I converted to electric using Kershaw direct drive, brushless motor, and 6S ESC and battery setup.

    The truck was running perfectly for about a year since the build, then it sat for a couple months and now has this issue that I've been troubleshooting for a while.

    When I first plug in and turn on the truck everything seems fine. FWD and REV are fine and I seem to have full power. Then within the first 5-10 seconds of runtime the max throttle output clearly starts being reduced. Then within 10-15 seconds the throttle only produces motion when the first 25% of the throttle travel is used. After that point on the throttle it is like the ESC prevents current from passing. It doesn't shut off. It just doesn't go. Doesn't make any sound.

    Then slowly the throttle becomes less and less effective until the truck just won't go at all, at any throttle amount.

    If I let the truck sit for a moment, it will go again, but the behavior resumes very quickly. And it is always progressive.


    If I unplug and restart then the whole process starts over again, beginning with full power output.

    I've been messing with this for a year trying to trace the cause. I've basically rebuilt the truck and still the issue persists!

    I even use this radio for multiple vehicles so it shouldn't be the radio as it works fine in other cars and bikes.

    I'm at a total loss and could really use some advice. I've been into r/c for decades and consider myself skilled, being able to fix 99% of what comes along. But this has me totally stumped.



    As far as I can tell the direct drive is fine. Clutch is fine, alignment is fine, and everything turns as smooth and precisely as the day I installed it.

    I've swapped motors (the original Medusa and a new CC, ESC's (both Mamba Monster), BECs (all 6V ParkBEC), and batteries (all MaxAmps 6S (2 x 3S).

    Nothing is binding in the mechanicals. The ESC is programming fine. The motor seems strong. And the wiring is correct.


    What could be causing this? I've replaced ALL the electrics. I thought surely that would fix it even if I never discovered the root cause, but no. Please help!


    Thanks!



    -Smoky

  2. #2

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    bad esc would be my guess, sounds like the lvc is kicking in when it shouldn't be. really the answer is in your question, you have changed everything but the esc...lmao
    I was going to say bad batteries but you changed them.....right.....?
    oversteer scares passengers, understeer scares drivers!-savagex,-savagexl,-savageflux,-revo3.3,-tmaxx3.3,-losi aftershock ltd

  3. #3

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    I changed the ESC too. Went from Monster V1 to V3 or whatever the latest is.

    Sorry if that wasn't clear.


    I've swapped motors (the original Medusa and a new CC, ESC's (both Mamba Monster), BECs (all 6V ParkBEC), and batteries (all MaxAmps 6S (2 x 3S).

    Only electrics I have not swapped is the steering servo and the rx. But I don't see how either of those could be involved.


    Thanks
    -Smoky

  4. #4

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    hmm, it really sounds like bad batteries....i would bench test the input voltage going to the esc with a meter and see what the voltage drop is under load while its acting up. If the voltage stays at or near 22 volts then the batts are good, if it drops below 18 volts then the batteries are bad.
    oversteer scares passengers, understeer scares drivers!-savagex,-savagexl,-savageflux,-revo3.3,-tmaxx3.3,-losi aftershock ltd

  5. #5

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    I'll check that out. Can I just attach a meter to the balancer plug on each 3S pack?

    I have tried two different pairs of packs. Discharged and recharged both. Usuually my charger would detect issues. But they are a year or two old now.

    -Smoky

  6. #6

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    Disconnect the servos and bench run it. Maby they are heating up and creating a large draw that is killing everything. then once it cools for a few it starts to work again.

  7. #7

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    I touch everything when this is occuring....everything. All electrics, wires, joins, solders...everything is COLD to the touch, especially since the issue begins occurring almost immediately.

    I've checked my solder joints and connectors...I do all my own work and am pretty good at soldering nowadays. I don't see any issues. Even when I look at the joints under a magnifying glass I see no cracks or fatigues.

    Good ideas to check those things though!

    To be safe, I am replacing the batteries with NEW ones. I was trying different 3S packs to make a new combo but I bought all these packs around the same time so maybe they are all bad. Just a couple years old though on each pack. Maxamps batteries. I would have expected them to last longer at that price.

    I am also going to replace the series connector, just to be ultra-complete.

    Part should arrive soon. I'll follow up here. Thanks everyone!
    -Smoky

  8. #8
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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    Try resetting your   "end point"  adjustments in the  ESC,   in sync with the Tx. 

    Frank

    AMA #5810
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    Contest Director
    AMA Introductory Flight Instructor

  9. #9

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    Ive done several resets. Is there a way to manually check endpoints on the ESC?
    -Smoky

  10. #10

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    definitely sounds like a battery issue that is the only common thing between all your testing with the ESC's. The only other thing i don't see is if you switched out the receiver? you say the transmitter works fine on other veh but im assuming that you have different receivers in each veh maby swap one of them into the trouble veh and vise versa?

  11. #11

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    I tried two different pairs of LiPos, fully discharging then sync charging each pair combo before each test. All tests failed, but the batteries were purchased at the same time a couple years ago so maybe they both went bad at the same time.

    I have new batts on the way, and a new series harness, to test in place of the one I built. If swapping those doesn't help then I will try swapping the rx as you suggest.
    -Smoky

  12. #12

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    Great thread,Thank you to all those who posted...., keep them coming : )


  13. #13

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    RE: Need some help: Fully custom build was fine, now having throttle range issues

    'twas the batteries! And now I look at my other Maxamps batts and they are getting puffy. So that, I am guessing, means I'll be tossing all of my Maxamps batteries that are older than a year. A YEAR AND A HALF I got out of these. Seems kinda short for the price. And its use-it or lose it, because I don't have a lot of bashing time or flight time. Just a little here and there when I can sneak it in around family obligations. Yet they still died.

    FOUR batts I was trying. And I tried in every combo so that means there are no good batts. I could test each cell and reassemble the "good" cells but how long till they go bad as well? Not worth the effort. No more Maxamps I guess? Kinda sucks because they do offer some nice choices and packaging options. But at the price it isn't worth it for not even making it two years.

    Thanks to all for the excellent help!
    -Smoky


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