ESC questions.

[Stuart Linfoot]

I'm not sure if this is where I should post this or not but here it goes anyway.

I just got a Midwest Liberty Tug, and I noticed that the drive system that comes with it has a 12 volt motor, and runs off of 2 6 cell car type battery packs.

I have a couple of car ESC's that I was wanting to use in it but I'm not sure either one of the ESC's can handle 12 volts, one is a Super Rooster Reversable, and the other one is one of the cheaper Futaba speed controls, (can't remember the model number of this one though)

I know that both speed controls work fine with 540 size motors, and a single 6 cell car pack, but will they work in this boat aplacation? or should I be using a car type motor if I'm going to run either of these speed controls?

[LtDoc]

Stuart,
Either ESC would work in a boat, but you'd better check the specs of both for the voltage ratings. I think 12 volts would be a bit much for either of the ESC's, but you should check to be sure. The 12 volt motors will work on less than 12 volts with reduced performance. Not a 'good' option, but still an option...
- 'Doc

[CG Bob]

Novak Super Rooster specs from Tower Hobbies:
SPECS: Voltage input: 6 to 10 cells (7.2-12V) On-resistance: .002 Ohms
BEC voltage: 6.0v/3Amps Weight: 4 OZ
Maximum current: (forward) 320A (reverse) 160A
Case size: 1.63" x 2.02" x 1.22" Rx wire length: 10.5"
Batt wire length: 13" Motor wire: 13"
Wire Gauge: 14 yellow (+), blue (-)

6 cell Nicad or NiMh batteries put out 7.2 V (6 cells @ 1.2V/cell).

[martin richards]

It's not usually volts that fry esc's but amps. However, max amp ratings for esc's usually owe more to the marketing department than the technical guys.
In any case, for a 25" tug set up you would only be drawing possibly 5 amps max on a standard 500 size motor running on one set of 6 NiMH cells.

[patmat2350]

You do want to pay attention to the max volts rating! While the power-handling part of the ESC (the "FETs") care about amps, the logic side, and reverse spike protection components care about the applied volts... I asked Airtronics about running their tiny ES-01 on 12v instead of the rated 8.4v max, while observing the 3A limit... they said DON'T DO IT.
Pat M

[Dragooneye]

When dealing with electronics the two most important aspects are the Voltage and current ratings. The voltage ratings of the source (battery, wall socket, power supply) and the device should match to get the best usage out of the device. For current; the source can have more current then the device and be fine. So a source with 12V 50 amp rating and a device with a 12V 2 amp rating will work, because the device will only draw the 2 amps that is required to run. If the source has less current then what the device requires the device will not work or will work slow. So a 12V 2 amp source and a 12V 20 Amp device will NOT work, because the device is trying to pull 20 Amps from a 2 amp source.

In this case the 12V motor is run off a 2 6 Cell batter packs as stated above a cell is 1.2V. 6 * 1.2V = 7.2V a pack. 7.2V * 2 = 14.4V when the battery packs are placed in series. Motors can take over voltage usually as they will run fast and slow down as the voltage drops off back to 12V and then lower as the battery looses it's current. ESC should be able to handle the 14.4Volts for a little while as they are usually over engineered to allow for the variance in battery voltage of a few volts, but that is just my experience working with electronics.

As for the post above. Running a 8.4V off of a 12V is too great a range for the internal components to handle. Usually electronics are a + or - 10% tolerance of ratings in components. The voltage in that respect was way to much and would blow the components.

Hope this helps...any other questions let me know.

[cop56]

Stuart,
I have the Liberty tug. It runs forever on one pack.The second pack is just something to hassle with. I just centered the one forward and adjusted the ballast. I using an old
Futaba 210 esc.Works fine.
Fred

[ropanach]

For those of you whom haven't been introduced to Dragooneye, he has a batchulars in electronics. I pick his brain when ever mine dosen't work (witch happens alot lately),

[Stuart Linfoot]

My thinking was to use one of the motors out of one of the RC cars I have, those motors are about the same size (physical size) as the motor that came with the boat, but the car motor was running on those ESC's and a single 7.2 volt battery pack.

I'm really not wanting to spend money on an ESC for the boat if I can some how use one of the ones I already have out from the cars.

I'm no expert on motors by any means, so I don't know the difference between windings on the different motors, or currant draws and so on.

The motor in the liberty tug is a direct drive, and the motors out of the cars are housed in gear drive systems, so I don't know if taking one of those motors and using it in a direct drive system on the boat is going to make any difference or not.

I'd like to be able to get some sort of run time out of the boat, and when these motors were used in the cars, I had maybe a 7 minute or so run time with them, and I'd really like to be able to do better then that with the boat, at least with using the car motor, I'd be able to run it on a single pack, or maybe hook two packs up to run in parallel?

[Capt_Christo]

I am building a 750mm tug. the prop scales off the drawing at 40mm. What would be a good motor/drive/esc combo. I would like reasonable bollard pull on this boat.

Any recommendations?

[Umi_Ryuzuki]

If you have to choose one from what you have, the super rooster is what I would recommend. The rooster, then the super rooster were two speed controls I never got around to buying. But the capacity to run 12v or 10 cells are alway one the first considerations I make when choosing an ESC.