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Nov 22, 2015, 09:55 PM
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can a Dumas 2004 6 volt motor handle 2s lipo ?


wondering if the Dumas 2004 motor rated at 6 volts could handle a 2S battery ?? not racing or pushing things to the extreme in a tug boat..
kevin
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Nov 22, 2015, 10:20 PM
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patmat2350's Avatar
I run the motor on 7.2v NiMh, no prob... 2S = 7.4v, meh.

It's not just about voltage though, it's about the load generated by your prop.
Nov 23, 2015, 04:26 AM
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A lot depends on your style of driving. If it works OK on 6 volts, indicating that the right prop for the motor is fitted, demanding the same performance will work just fine but leave a bit more power in reserve. Habitual constant use of the extra power might well shorten the motor's life, especially if there is too much prop putting too big a load on.
Another bit of depending comes from just how conservative Dumas were when writing the motor spec.
Nov 23, 2015, 10:39 AM
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There is no problem running a Dumas 6 volt motor on 7.2 volts of power for any length of time. The Dumas motors which are either Mabuchi or Pittman motors, are rated the standard of 50 percent over voltage range. This is why Mabuchi motors used in R/C car models can run 6 to 8.4 volt batteries with no problems.

If your model was running with a 6 volt motor with the same prop and hardware you are now going to run with a 2 cell LI-PO battery (7.2 volts), the only difference you will see is the increase in speed (rpm’s) due to the 1.2 volt increase in voltage. The LI-PO battery has a much greater capacity as far as discharge amps but the motor will only use what the speed control is rated for.

You must remember that when you switch over to LI-PO batteries you must make sure that your speed control has a voltage cut off or you must put a settable voltage alarm or cut off so as not to damage the batteries during discharge.
Last edited by frankg; Nov 23, 2015 at 11:38 AM.
Nov 23, 2015, 11:12 AM
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thanks for the feedback guys....I have a decent ESC that is set up for Lipos..
kevin
Nov 27, 2015, 02:43 AM
Just Plane Nutts
AirDOGGe's Avatar
I have a similar motor in my little Steerix boat, and I swapped the 6v nicad for a 7.4v lipo with no problems so far.
Nov 27, 2015, 02:47 PM
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Like has been noted above, you are jumping from 6v to 7.4v. That IS, a 25% increase in voltage, and, what worked great, on 6v, may be OVERWORKED now. I would check your amp draw, at full throttle while held in place, and also monitor, your motor temps. Slightly, to moderately warm, is OK, hot to the touch, is not.
Nov 27, 2015, 11:06 PM
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One thing to remember is that a 2S Li-Po in good health and fully charged puts out 8.4 volts, not 7.4 volts. The 7.4 volts that many refer to is a nominal voltage. Sort of like the battery in your car is called a 12 volt battery but in a fully charged state puts out about 13.2 volts.

I think that running the motor wide open for any length of time would destroy the motor.

If we say that the motor draws 10 amps at 6 volts than the motor is using 60 watts of power, power = volts times amps. If the voltage increases to 8.4 volts, then ohms law states that the current draw would increase to 14 amps. We now have 14 amps at 8.4 volts which is 117.6 watts, almost double the power consumed by the motor at 6 volts. While I don't know the current draw, and power usage of the Dumas #2004 motor at the rated 6 volts, it would be greatly increased at 8.4 volts.

While a 2S battery would work, you would want to be careful and experiment a bit to determine how much throttle you could give it. If your radio has a programmable throttle that would be one way to limit the voltage to the motor.

Mike
Nov 28, 2015, 01:20 AM
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CaptCB's Avatar
If you are using the Left, Vertical Stick for throttle, like most of us do, it probably is NOT programmable. As it is designed to control a gas engine, in an airplane or heli. None have Exponential, and most, do not have "End Point Adjustments" either.
Nov 28, 2015, 03:40 AM
Just Plane Nutts
AirDOGGe's Avatar
Quote:
Originally Posted by catman1
One thing to remember is that a 2S Li-Po in good health and fully charged puts out 8.4 volts, not 7.4 volts. The 7.4 volts that many refer to is a nominal voltage. Sort of like the battery in your car is called a 12 volt battery but in a fully charged state puts out about 13.2 volts...
True. I've even measured 14 volts in a car battery after charging. But fresh 1.2 volt Ni-cads measure higher than their rating as well, usually 1.4 volts when fully charged.

That means the 260mah, 6-volt, 5-cell Ni-cad pack that came with my Steerix boat will measure 7 volts at full charge, so the overall voltage increase the motor sees is still in the 1.4v range.



Quote:
Originally Posted by catman1
...I think that running the motor wide open for any length of time would destroy the motor.
Extra heat is a killer, no doubt. Because of this, I added a generous dab of thermal grease between the motor casing and the aluminum cooling tube, to help remove more BTUs. We are racing 2 boats together, and so far it seems to be working.
Last edited by AirDOGGe; Nov 28, 2015 at 03:46 AM.


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