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Thread: hot batteries

  1. #1
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    Default hot batteries

    Leopard 3650
    2- 3s- 2200 lipos
    90a esc
    Outboard from OSE

    Each time I go out, the boat is sluggish and not fast. Sometime the throttle quits but then restarts right away on its own. When I open up the boat, the batteries and wires are very hot.
    Why is this happening?
    Is the motor too big, too small?
    Is the ESC not big enough?

    Thanks for any suggestions

  2. #2
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    Default

    What is the 'C' rating on the batteries?


    ~ More peace, love, and kindness would make the world a much better place

  3. #3
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    I use 60c and 50c
    How could C rating affect heat?

    Do you know about timing of the ESC? I have a program card for ESC and wonder if I change the timing.

    Thanks

  4. #4
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    Quote Originally Posted by bmd8991@aol.com View Post
    I use 60c and 50c
    How could C rating affect heat?
    Lowering the motor timing (through the ESC) could help...but, my guess is, the batteries are the core of the problem. A crawler will get 45 minutes on a 5000mAh pack, while your typical basher will get 15-20 minutes on that same battery. You'll be hard-pressed to get more than 4 minutes on that same battery in a boat. Why? Because the energy is 'sucked' from the battery a LOT faster.

    The 'C' rating represents the battery's resistance...the lower the 'C', the greater the resistance. A crawler uses very little power, which is why a 35C pack is more than "good enough" for them. Your typical basher uses more energy in the same period, which is why it needs something in the 50-90C range. A 'pleasure' boat needs at least 60-75C, while a race boat probably shouldn't have anything less than 100C. When you use a battery with a lower 'C', as stored energy departs the pack faster than the pack can handle, it generates heat, due to the resistance. The greater the resistance, to the greater the heat generated.

    Moral of the story: Get battery packs with higher 'C' rating.


    ~ More peace, love, and kindness would make the world a much better place

  5. #5
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    Default

    Some key info missing here. 3S series or parallel? KV motor? Prop load? Size and weight of boat? What are speeds your seeing and run time?
    Mic

    Mic Halbrehder
    IMPBA 8656
    NAMBA 1414

  6. #6
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    Default

    Agreed, more info needed. Most likely it's a combination of capacity and C-rating, but no idea if you are running a tug or an FE.
    Also, what is your definition of hot? Get a cheap temp gun, don't rely on fingers.

  7. #7
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    Here is more info-
    28 inch wooden tunnel hull (previously nitro)-
    Running 2-3s in parrallel
    2200/ 60c
    run time 4 minutes at up to full throttle
    3650 kv
    Do not know speeds or weight of boat- it is wooden
    Definition of hot- cannot pick up batteries and wires to the touch!!
    Do I have too much battery for the Kv?
    Thanks for help

  8. #8
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    Hello Brian, You didn't tell us what prop you're running.
    If by "too much battery for the KV" you mean voltage, yes. Capacity, no. 3650 kv on 3s is a pretty hot set up without a lot of motor. Combine that with a 4 min runtime and 4400 Mah on board my guess is you are knocking the bottom out of those cells among other things.
    How much capacity was left after a run? (You want 20% min, if you want them to last)
    What are the motor ESC temps after a run?
    2700 - 2900 kv would be a better choice or drop back to 2s prop

    Have fun and good luck!!
    MODEL BOAT RACER
    IMPBA President
    District 13 Director 2011- present
    IMPBA National Records Director 2009-2019
    IMPBA 19887L CD
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  9. #9
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    Default

    Doug
    That helps alot. The prop came with the outboard- cnc-3814250- 38mm.
    Capacity after running is at 3.8v or so.
    Never measured the temp of the ESC, motor, or batteries. Will have to figure out how to do that.
    Will try 2s tomorrow
    Thanks for help

  10. #10
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    Default

    https://blog.ampow.com/lipo-voltage-chart/
    3.8v/cell or so puts you down around 10 to 15% or so.

    https://www.offshoreelectrics.com/pr...od=hh-dynf1055 or similar

    135 to 140'F max is where I draw the line.

    https://www.offshoreelectrics.com/pr...y-Cell-Meter-7 or similar

    Good luck!

    D.
    MODEL BOAT RACER
    IMPBA President
    District 13 Director 2011- present
    IMPBA National Records Director 2009-2019
    IMPBA 19887L CD
    NAMBA 1169

  11. #11
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    3.8V is a little more than 10%, it's ~40% and still plenty of minutes of fun left in the pack.
    Agreed, 135-140F on the Lipo is about as high as you ever want to see it go.

  12. #12
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    [QUOTE=jkflow;758612]3.8V is a little more than 10%, it's ~40% and still plenty of minutes of fun left in the pack.
    Agreed, 135-140F on the Lipo is about as high as you ever want to see it go.[/QUOTE

    You are correct. (difference between .4 and .04 old tired and a little dyslexic ) Personally, I don't ever want to see my batteries at that temperature. Mine are seldom much over 100' after a heat race.
    The temperature reference was to Brian and in regards to the motor and ESC max temp. And personally at those temps, I'm working on getting them down closer to 130'. But to each his own..
    MODEL BOAT RACER
    IMPBA President
    District 13 Director 2011- present
    IMPBA National Records Director 2009-2019
    IMPBA 19887L CD
    NAMBA 1169

  13. #13
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    Default

    I'd probably start by picking up a low cost IR Temp gun (Amazon or Harbor Freight?). Check the wires, connectors, various areas of the motor, the ESC, and areas of the driveline incase of some high friction spots.
    Heat is relatively unknown until you measure/read it correctly. To me 115F is too hot to handle, but ok for these electronics.

    Connectors can be a restrictive point that causes heat. Lower mAh batteries have a tendency to come with connectors made for 40-60a applications.

    What type of connectors are you running?

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