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Old Nov 09, 2010, 06:49 PM
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Windsor, Canada, near Detroit
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great advice, gambler

well, this is even better of what i wanted. thanks a lot.
i always like to understand things. now i know.
but, considering all the equipment needed and its cost, and the tests, for the price of the cells, 1 rather let them die and replace them.
but i needed to know all about it.
thanks again, great guy.
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Old Nov 09, 2010, 06:57 PM
Gopher huntin' stick jockey
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East Bethel, MN USA
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Quote:
Originally Posted by RealGambler View Post
Now, so you can relax your brain after my previous msg, I'm giving you a video of my Sukhoi V1, with a SP motor in it. As I said before, I got two motors from Hobby King. One is very quiet, as other have said before... I would even also say it's a bit quieter than the original parkzone motor as well. But my second one is extremely noisy! That's the one I've installed in my Sukhoi. It's powerful, and it does sound like I have a 12 cylinder under the hood now! Trust me, the video does not even give you the full sound (it's taken with a cheap keychain type camera, so bad microphone and very bad audio sampling rate).

So basically, if you ever get some motors and you get a noisy one in the bunch, go for it. Only slightly over 30 flights, so not sure yet how long it will last, but wow, just listening to the sound, your plane seem to go faster

Enjoy
RG,

Nice flying! Wow, that motor is noisy. Sounds like a Skilsaw with wings... What did you put the quiet motor in?

Joel
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Old Nov 09, 2010, 06:57 PM
**I'm Battman**
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Twin Falls, Idaho
Joined Jan 2005
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Chime Time:

Two of my V1 Turnigy 160s just died on me a few weeks ago.
No warning at all.
I think they died from young age.
Personally I'm done messing with low grade cells.
Hyperion & Thunder Power are all I fly now.



rc
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Old Nov 09, 2010, 07:15 PM
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United States, IL, Washington
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RealGambler
You took that video in the exact same place just so you could here me coment on that ''BIG ASS SNAKE'' again didn't you. LOL
TODD
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Old Nov 09, 2010, 09:21 PM
Way to many airplanes!
Canada, QC
Joined Oct 2009
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Originally Posted by phil alvirez View Post
well, this is even better of what i wanted. thanks a lot. i always like to understand things. now i know.
No problems... I had to remove some rust inside my brain to do that, so it was good for me too!

Quote:
Originally Posted by turboparker View Post
RG,

Nice flying! Wow, that motor is noisy. Sounds like a Skilsaw with wings... What did you put the quiet motor in?

Joel
The quiet motor is still waiting for a plane... Currently, it's on one of my friend's desk I can trust to count the cycles if he ever install it in his Mustang, who's actual motor is currently drawing close to 2 amps!!! But the longer he wait, the more likely one of my ultra-micro will need it, so there's a string attached!

I truly love the noise!!!!

Quote:
Originally Posted by JohnM View Post
Is it a gear mesh problem?

John
Doesn't look like it... Doesn't make much noise when I manually spin the propeller, and it does spin VERY VERY easily too! My Sukhoi XP is currently twice as hard to spin manually. No matter what, the motor was really noisy before installation, without the gearbox. If it doesn't last long, I would say that we should not count it in the stats since there was obviously a problem with it, but so far, it does fly as well as any other motor. And again, the video does not do justice... This is an AIRPLANE with capital letters! Heck, I have an EDF that my friends call "the hair dryer" that make less noise than my UM Sukhoi! But I love it!

Quote:
Originally Posted by I R Irv View Post
RealGambler
You took that video in the exact same place just so you could here me coment on that ''BIG ASS SNAKE'' again didn't you. LOL
TODD
That's my favorite spot, and YES, everytime I look at the snake in any of my video, I alway hear you laugh! But c'mon, it's a nice smoooooth landing spot. Now, if I can only learn to land properly. As you can see on the video, I crash more than I land on it! Still, never crashed into the snake, so I figure he is my control tower! Lately, we had a bit of snow (that melted away)... That snake look much better with a white hat!
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Old Nov 10, 2010, 03:50 AM
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Windsor, Canada, near Detroit
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dying

Quote:
Originally Posted by RCBABBEL View Post
Two of my V1 Turnigy 160s just died on me a few weeks ago.
No warning at all.
I think they died from young age.
Personally I'm done messing with low grade cells.
Hyperion & Thunder Power are all I fly now.



rc
rc: i want to learn more about what 'died' means to you. what were the signs? what are their volts figures? the 2 of mine that i mentioned still show good voltage but the motor stops 5 seconds ater i launch, so for me, that's 1 way of dying, not being useful anymore.
why mine still show good volts? perhaps somebody can help me there.

turboparker: i fly at no more than 60-70% for take-off and climb and then 50-maybe 30%-the rest of the flight, so the cheap turnigy do the job for me. even if some die now and then. i just am curious about all of this.
thanks
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Old Nov 10, 2010, 05:35 AM
Way to many airplanes!
Canada, QC
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Quote:
Originally Posted by phil alvirez View Post
i fly at no more than 60-70% for take-off and climb and then 50-maybe 30%-the rest of the flight, so the cheap turnigy do the job for me. even if some die now and then. i just am curious about all of this.
thanks
Phil, you may want to try going Wide Open Throttle all the time with the Turnigy. They are about as much sensitive to cold as the Parkzone 120mah. If you don't go WOT while flying they loose even more capacity as they are cooling off. You're in Canada, and currently, we have temperature close to the freezing point.... Sure enough, as I said, they also had some bad batch of batteries, so maybe you're simply unlucky, but at least give it a shot. You may get much longer flying time.

Otherwise, RC was right.... Hyperion are the best ones in the cold (I've not tried TPs, but I've tried pretty much everything else...) Amazingly enough, currently my nano-tech are my second best choice IN THE COLD... They seem to do very decent until I get close to freezing, then, boom, one less degree and they are dead. So they won't be good for our winter (always below freezing) but late fall and early spring at least.
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Old Nov 10, 2010, 06:35 AM
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take cover

Quote:
Originally Posted by RealGambler View Post
Phil, you may want to try going Wide Open Throttle all the time with the Turnigy. They are about as much sensitive to cold as the Parkzone 120mah. If you don't go WOT while flying they loose even more capacity as they are cooling off. You're in Canada, and currently, we have temperature close to the freezing point.... Sure enough, as I said, they also had some bad batch of batteries, so maybe you're simply unlucky, but at least give it a shot. You may get much longer flying time.

Otherwise, RC was right.... Hyperion are the best ones in the cold (I've not tried TPs, but I've tried pretty much everything else...) Amazingly enough, currently my nano-tech are my second best choice IN THE COLD... They seem to do very decent until I get close to freezing, then, boom, one less degree and they are dead. So they won't be good for our winter (always below freezing) but late fall and early spring at least.
thanks, gambler. your advice is highly appreciated. you are right. but i can't go wide open with my planes: they would go to the moon in no time. besides, about the cold, as i mount my cells on top of the side piece of the fuselage of my planes (structure similar to 4site) and make a 'box' with epp to hold them in place, the cold does not reach them very much. that's why i get such good times, even if flying below freezing, as i do, and most of my 160's are doing well. perhaps the failing ones are just below standards, as happens with low (or no) quality control manufactures. on mass production of low cost products, they check just 1 in let's say 100, if they check any at all.
i will be testing nanos next time there is no wind here and i will tell.
and the sp is doing fine, just its noisy self.
regards
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Old Nov 10, 2010, 06:25 PM
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East Bethel, MN USA
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Phil,

Regarding the normal unloaded voltage and poor performance under load: This is the classic sign of a cell with a high internal resistance. Since all batteries have some internal resistance, they will exhibit a voltage-drop when under load. Assuming a constant load - the higher the internal resistance, the higher the voltage-drop. Also - the higher the current, the higher the voltage-drop. This wasted energy is dissipated as heat within the cell. As is true for most battery types, a LiPo cell's internal resistance will typically increase as it nears end-of-life. At some point, the internal voltage-drop becomes significant enough to cause problems. The higher the load, the sooner the problem becomes significant. Hence, why battery performance tests should be done under a typical load. (This applies to all battery types - not just LiPo.)

Also - a LiPo cell's internal resistance temporarily increases as the cell is cooled. This effect is much more pronounced as the cell nears the freezing point. This is why, at near-freezing temps, a couple of degrees can make a big difference.

Hope this helps!

Joel
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Old Nov 10, 2010, 08:36 PM
HELP I AM BEING SET UP!!
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noisy SP motors rule!

FWIW- just wanted to chime in that the SP motor I am "currently" (har har pun intended!) running is one of the noisy ones...love it!

4 pieces of carbon reinforcement in various places, Crystal Clear hinge tape in other strategic locations and around a half a tube (!) of UHU Por...that's a lot of extra weight...BUT...with the SP motor and fresh batts the ol' dawg actually can still hover and even power out of one! Quite amazing actually. :thumbsup!:

The weather window here has slammed shut with a bang...we had snow yesterday and it's barely getting above 40F daytime temps, 20s' @ night now.


Bud, hoovering Bud
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Old Nov 11, 2010, 04:17 AM
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post 84

turboparker:
great explanation! am sure many of us will benefit from it. we all need to understand what's going on.
now, what do you suggest to use as typical load for testing a cell?
more specifically, let's say, a turnigy 160, which seems very popular among um's.
and how we make this load? with a certain capacity resistor, or what?
how we connect it? as many details as possible will help.
thanks a zillion for the input.
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Old Nov 11, 2010, 08:22 AM
Way to many airplanes!
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Yeah, time for me to fill your head with more math!!!

I would use a simple resistor since using an airplane add too much variables into the equation. So, you want to test the battery in it's typical application (UMs draw between 1.3 to 1.6 amps. Some bad motor will go close to 2 amps!). But you could also test a battery for what it is rated for.

So let's go for reaching a certain current first. (typical application, so 1.5 amps)

Voltage fully charged: 4.2Volts
Current we want to draw: 1.5 amps.

Resistor needed: voltage/current so: 4.2/1.5 = 2.8 Ohm resistor. You could likely use a 3 Ohm resistor. You need a lot of power though. Power is equal to Voltage*Current through the resistor, so in this case: 4.2*1.5 = 6.3Watts resistor. Ideally, you would go for a 3 Ohm 10 Watt resistor.

Now, solution two is testing if a battery is really rated as good as it is on the label. Let's take an Hyperion 160mah 25C.... It should be able to provide 25*160mah constantly.... So 25*.160 = 4 AMPS! To find out if it's still has the guts to do it (and it will most likely will, so be careful), you need to find the resistor to draw that much current... Same formula above:

Resistor needed: voltage/current so: 4.2/4 = 1.05 Ohm resistor. So I would go for a 1 Ohm resistor. Now, you're drawing more current into it, so more POOOOWER! Power needed is 4.2*4 so this time we need a 16.8 Watt resistor minimum. I would likely go for a 1 Ohm resistor 20Watts, or even 25watts.

So basically, once you've decided what kind of current you want to draw, then it's only a question of plugging everything with an ampmeter (multimeter on amp...). When you check many batteries, they should all come in the ballpark of the current you're expecting. Let say you get 3.95, 3.97, 3.87, 3.91, 3.40, and 3.89 amps, then you can safely guess that battery number 5 has a huge internal resistance. You could even calculate it with some decent accuracy if your 1 Ohm resisntance was a 5% or less accuracy... Let say that after you connect the resistor to the bad battery, you get 4.0V with the 3.40 amp... Total load would be: 4/3.4: so 1.176 Ohm. If we assume your resistor was very accurate at 1.000 Ohm, then the internal resistance is 0.176 Ohm, or 176 milliOhm...

Warning: As usual, I may be totally wrong with my calculations. You may also burn your fingers on some of those resistors. And I would wear eye protection at all time. And I would put a fire extinguisher beside my bench, and.... bla bla bla, you do at your own risk!
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Old Nov 13, 2010, 03:56 AM
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great advice

gambler: terrific advice, as usual. thank you very much. now i have enough to play with and learn.
3 more cells died yesterday. they were same batch.
i have been using the cirrus esc, that has a 2.6v lvc, so when i use a cell of different capacity or type that i have not tried with it, i run it only once to lvc, to know at what time it does it, and then i run the others 1 minute short, so i don't get close to lvc anymore.
as i am running the 3 motors (clear, black and grey end bell) alternately, i think that after breaking-in them, eventually i will get a better feeling of their differences, and in the meantime am having fun just flying and catching my planes.
regards
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Old Nov 13, 2010, 05:46 AM
Way to many airplanes!
Canada, QC
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Originally Posted by phil alvirez View Post
gambler: terrific advice, as usual. thank you very much. now i have enough to play with and learn.
3 more cells died yesterday. they were same batch.
i have been using the cirrus esc, that has a 2.6v lvc, so when i use a cell of different capacity or type that i have not tried with it, i run it only once to lvc, to know at what time it does it, and then i run the others 1 minute short, so i don't get close to lvc anymore.
as i am running the 3 motors (clear, black and grey end bell) alternately, i think that after breaking-in them, eventually i will get a better feeling of their differences, and in the meantime am having fun just flying and catching my planes.
regards
Woooooweeeeeeee...... That's awefully low for LVC for sure. I think you're right about timing your flight very carefully.

Recently, we have started flying some Flightmax batteries that have probably 100 cycles in mSrs and then got shelved unused since then. They still work and fly a Mustang! So basically, discharging batteries too much is truly their worst ennemy!
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Old Nov 13, 2010, 06:36 AM
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I concur with RG - over-discharging is the quickest way to kill a LiPo. The recommended maximum discharge for all LiPo cells is 80%. Discharging beyond 80% even once may reduce the performance and/or longevity of the battery - however, most modern quality LiPos seem to be able to handle an occasional discharge to, say, 85-90% with no ill effects. An LVC of ~3.4V would be much healthier for the cells.

A few comments on load-testing....

Using a resistor is a good method; however, the current is dependent on battery voltage, so the current decreases as the battery discharges. This makes it more of a pain to calculate usable capacity. Many hobby-grade multi-chargers also have a discharge function that applies a constant-current load to the battery. This more closely approximates real-world use. (As the battery discharges, most pilots increase throttle to maintain a given power level.)

More thoughts on using resistors...

A 20-25W resistor that's dissipating ~15W will likely get hot enough to cause second-degree burns, if touched. Do not let the resistor touch anything that's heat-sensitive or flammable. One should use a 'power resistor' - not just a simple carbon or metal-film resistor. Power resistors are typically encased in metal, and usually have a heat-sink.

Joel
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