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12-19-2003 06:31 AM  13 years agoPost 1
blueeyedpop

Senior Heliman

westlake village, CA

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Hi Group.

Hummingbird v2
370 gold motor
century Li Ion battery(s) with less than 30 cycles each.
Stock blades

When I first power up, I have full power, but after about 30 seconds, there is not enough "juice" to hover above 6". THis lasts for another 45-60 seconds, them power returns to normal.

I have cleaned all the contacts, replaced main motor, and can only think it may be an issue with the mixer/speed control.

Any thoughts?

Mike

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12-19-2003 09:23 AM  13 years agoPost 2
Gazoo

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Maryland

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It could also be the battery. The century Li-Ion does not put out enough current.

If all else fails, do what every one else does and get Etec batteries. I always recommend the Etec 2S 1200 from lightflight to start with because they are packaged very well.

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12-19-2003 10:43 PM  13 years agoPost 3
blueeyedpop

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westlake village, CA

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Generally speaking, when batteries are cold, they cannot reach their rated discharge current. This is why your car battery fails during the wintery months.

I have been charging and flying in the warehouse here at work, where it is down into the mid 50's. Since the packs are rated at 800 mah, and the discharge rate of a li Ion battery is 2C, under very best circumstances, I will be limited to 1.6 A.

As an experiment, I charged up a pack that had been giving me grief, warmed it up in my pocket for 20 minutes, and guess what, it works.

I guess I will be switching to Li Poly, which can discharge at up to 5C

Mike

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12-20-2003 05:51 AM  13 years agoPost 4
Gazoo

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Maryland

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I guess I will be switching to Li Poly, which can discharge at up to 5C
You will want to. Not only will you get better performance, the Lipo is safer.

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12-20-2003 04:33 PM  13 years agoPost 5
blueeyedpop

Senior Heliman

westlake village, CA

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People have recommended the 2 cell pack, which would be 7.4 Volts, which is less than the original birdseed battery. Century's Li Ion is a 3 cell pack, goving 11.1 Volts.

Wouldn't I be better off with a 700 mA or 1200 mA 3 cell pack, especially if I want to fly with MSC's carbon rotor blades? or should I get a pinion with a higher tooth count, risk disturbing the fixed mix ratio in the speed control, to increase my bladespeed?

Thanks
Mike

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12-21-2003 01:46 AM  13 years agoPost 6
Gazoo

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Maryland

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The biggest problem with three cell packs when using the Humming Board is that there is no way to set off the cut off voltage. If you run any battery below its rated cut off, you will ruin it. With the 2S battery it doesn't need to have a cut off because you will be in the rotor wash and know when it is time to land when the battery is depleted. With a 2S you don't want to run it below 6V. If you read the battery voltage after you have landed, you will get a reading of 6V or higher. Perfectly safe.
Century's Li Ion is a 3 cell pack, goving 11.1 Volts.
This is one of the reasons I wish Century would stop selling that battery. Most people that order it think it will be OK to use with a stock setup. Not true. The cut off voltage of a 3S is 9V. Going lower will ruin the pack. In addition there are other concerns involving the Century battery that you and I are well aware of.

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12-21-2003 02:21 AM  13 years agoPost 7
blueeyedpop

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westlake village, CA

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Cool, thanks for the advice.

I will look into building a voltage comparator circuit with a warning LED, and run the 3 cell pack.

Thanks
Mike

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12-21-2003 02:34 AM  13 years agoPost 8
Gazoo

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Maryland

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Good idea. Please let us know how it works out for you.

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12-21-2003 02:53 PM  13 years agoPost 9
blueeyedpop

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westlake village, CA

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Just from a community point of view, do you think a single LED that comes on at like 9.3V is good enough? or would a couple of LEDs be better.

I am working on a couple of circuits, but wanted opinions, as I will post the schematic when i am done.


As a matter of note, i do not recall there being any mention of a voltage limit on the packaging of the century Li Ion batteries. Pretty shoddy.

Mike

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12-21-2003 09:41 PM  13 years agoPost 10
Gazoo

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Maryland

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I would use a couple of bright white L.E.D.'s Another option would be to use the CC Pixie ESC. It is programmable.
As a matter of note, i do not recall there being any mention of a voltage limit on the packaging of the century Li Ion batteries. Pretty shoddy.
I know. They should not be selling them period. The alternative would be for them to sell a good 2S LiPo.

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12-21-2003 11:15 PM  13 years agoPost 11
blueeyedpop

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westlake village, CA

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I hape to have something prototyped after X-mas. I will let the group know.

Mike

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