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123 and Brush motor

Old 11-17-2008, 09:41 AM
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BillS
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Default 123 and Brush motor

123 and Brush motor

I have a hand me down Gentle Lady with a 500-brush motor and speed controller. The NiCad batteries have two bad cells.

Can 123 batteries be used with brush motors? This is my first experience with electric.

Bill
Old 11-17-2008, 10:12 AM
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Walt Thyng
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Default RE: 123 and Brush motor

The only relationship between battery and motor is whether the battery can supply enough amps to roperly power the motor. Since A123s can put out up to 60 amps in a burst you will have no problem with the motor. The issue for you will be the ESC. The Goldberg 550 can motor typically ran on 6 or 7 cells and pulled 25 amps. 7 NiXX cells =8.4 volts (7x 1.2). the nearest you can come with A123s would be 2 cells (2x3.5= 7.0 v) or 3 cells (3x3.5= 10v). If your ESC can handle 10v @ 25 amps, go ahead an fly. If not you have two choices (this is part of the amazing flexibility of e-power) on 3 cells you could reduce the prop size (pitch and/or diameter), if you go with 2 cells you could do the opposite and increase either pitch or diameter until you get the amps in the right range.
Walt

PS those old can motors can take a lot of abuse, plus they are cheap.
Old 11-17-2008, 12:05 PM
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soarhead-RCU
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Default RE: 123 and Brush motor

Bills:
I fly a 2X4 glider with a GWS 400 geared (on a power pod) and a GWS 480 ESC and 2 Mini (HS81) sized servos. I am running 4 cells of the smaller 1100ma A123 cells. I put 2 in the
nose (all there is room for) and 2 under the wing patched in series. Have had zero problems with this setup. Use the same prop as I did with 8 cell Nimhs, no heating of motor or ESC. I bet yours will run with the 3 cells just fine, most of the older ESC that I have used could handle at least 12volts, probably even handle 4 A123 cells. A 8 cell Nickel type pack hot off the charger is over 12volts. They are great packs for sailplanes as they are so tuff physically and electrically and their weight is the same or even lighter that Nicads or Nimhs.
Id start with a 3cell pack on your rig, should be almost a straight across swap, just check for motor heat on you first flight but I dont think you will have a problem!!!!!!

Happy Flying
Bob
Old 11-17-2008, 12:18 PM
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BillS
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Default RE: 123 and Brush motor

Thanks for the very informative answers.

Is there a prop chart that could be used as a starting point for prop selection? The ESC is an Electrifly C-35. From the specifications it appears to be capable of 10v and 25 amps.

Thanks again.

Bill
Old 11-17-2008, 02:23 PM
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everydayflyer
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Default RE: 123 and Brush motor

Here is a discharge test showing comparison of 3S A123 and 6 cell NiMh.

Charles
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Old 11-17-2008, 04:21 PM
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Walt Thyng
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Default RE: 123 and Brush motor

Your C-35 esc should handle three A123s with no problem. If you are new to e-power you should acquire two things: a watt meeter (Astro or Medusa recommended) and a predictor program. DMA has one on its site for free, but it's limited. E-calc is cheap and easy to use. Motor-calc costs about the same,but in my opinion is for the more advanced e-power flier. There is also a free online program called "Drive-calc which a lot of top e-power people advcate.

These programs will tell you what happens when you change parts of the power system. Thye ae only predictoprs,but they are very close.
Walt

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