ORIGINAL: asupervee72
i came to share and see what people would say.
Maybe you should have titled the thread and your questions a bit differently then.
ORIGINAL: asupervee72
Do you have an eagle tree logger? At full throttle about 1000 mah is used every minute after 2 min 40% of a 5000 mah battery is used up, if your batteries are still giving you 8 volts after 40% ( more in the case of the 3700 mah packs) then you have some amazing cells.
The use of CAPACITY has little to do with the output voltage.
LiPo's don't react like NiCD's and NiMH packs.
LiPo's output above their rated voltage for the first minute or two of operation then the voltage drops a bit and stabilizes around the rated voltage of the pack. There-after it decreases VERY slowly until you hit the voltage "Knee" on the curve where the cells drop off percipitously.
You should NEVER let LiPo's get to the latter point.
After 20-30% usage on my 5000mAh 14.8, 22.2, and other packs I still get very close to their rated voltage, But during those first minutes the voltage output is above that.
ORIGINAL: asupervee72
If the motor was more efficient energy wouldn't be lost as heat, or due to resistance which would result in higher rpm under load. So really efficiency and KV actually are directly related
Wrong.
KV is merely a measure of how fast the unloaded motor spins.
It tells you nothing about the efficiency of the motor at all.
You can have a 2800 KV motor that is highly efficient and one that is terribly in-efficient, yet in given situations the actual observed RPM's can be similiar or not.
ORIGINAL: asupervee72
Why would i want to pull 100 amps from a motor only rated to handle 50?
You keep missing the point.
You DO NOT - WANT - to run 100 amps, but because of the way you have things set up with your electronics, to get to the proper power levels and best efficiencies for your motor you would have to have it pull 100amps to get close to it's wattage rating which is rediculous.
You should be running the motor at about 80% of it's capacity under normal flight loads at high throttle. You're not anywhere close with your setup.
ORIGINAL: asupervee72
Im having a hard time understanding why pulling 50 amps from a motor rated at 50 amps is not effectively using it.
Your motor is rated for 50 amps at 750 watts output
So run the numbers
750 / 14.8v = 50A 41440 RPM
750 / 11.1v = 67A 31080 RPM
750 / 7.4 = 101 A 20720
Get it?
To get 750 watts or close to max power out of your motor you need to run a 14.8v pack.
OR you need to push 67A if you are using an 11.1v pack just to get the same...
Or you need to push 101A if you are using a 7.4v pack as you are now.
The problem is that the motor simply cannot spin fast enough to keep up with the KV rating using a prop, unless you go to a VERY small prop
20270 RPM is rediculously high for anything but a tiny prop or an EDF. Your motor doesn't fit what you are trying to do.
ORIGINAL: asupervee72
I think we can both agree that on 4s 41440 rpms is too much, while a gear box is a nice idea there simply isn't room for one, nor is there room for a 4s pack big enough to handle a 50 amp load.
Which is why that motor is not really suitable for the plane.
To use an analogy:
It's like putting a huge dragster engine in a Volkswagon. The Volkswagon will seem powerful, and can go faster than ever, but it will never attain the speeds that dragster engine can produce.
ORIGINAL: asupervee72
If you only saw how hard I was climbing yesterday you'd know i wasn't lugging around extra weight.
Actually it is lugging around extra weight. You could do better with a smaller lighter combo better suited to your 7.4v packs.
You're equating climb ability with unnecesarry weight. While the latter can affect the former, the two are not equal.
ORIGINAL: asupervee72
I have 2 2s 25c 3700 mah, 1 2s 20 c 3700 mah, a 2s 20c 3200 mah , 3 2s 20c 5000 mah pacs and a 2s 25-50 c 5000 mah battery which is also why I like my setup because i can utilize all of those batteries and have plenty of time at the field.
2s is an extremely low voltage for most RC planes. You will normally only find this voltage used for the micro aircraft. Likewise the motors that use 2S packs are for the micro planes.
You are better off and taking any two of the matched packs and with a simple cable turning them into a 4S pack. You don't have to do anything to the batteries themselves. The adapter does the job.
Two of the 2S 5000mAh packs will power a much bigger .32 to .40 sized aerobatic electric plane with ease.
e.g my old 48" Diamante flies with 14.8v ( 4S ) 3600 packs or with 4S 5000 packs and hovers at half throttle.
ORIGINAL: asupervee72
How will pulling 50 amps from a battery rated at 92 amps constant prematurely use up the battery? Its only 54% of its max rating, well within a safe limit.
To get the power levels that motor SHOULD run at, you would have to put a lot of wear and tear on your battery packs.
Your are not currently doing so, so your batteries are OK, but in the same breath you mentioned the voltage drop, which indicates that the packs may not be up to the task.
ORIGINAL: asupervee72
While i see that you have been a member for a good amount of time and have several post it doesn't mean you are right.
The quantity of time here and the number of posts are irrelevant...
What is relevant are the numbers. They don't lie.
You can pull up Motorcalc and verify what I've told you.
ORIGINAL: asupervee72
After all I was out shopping yesterday and talk was still cheap, unlike the option you suggested which would require spending 40+ bucks on just mounting hardware and then buying an additional plane.
More non-sequitors.... You asked after all about "problems" with your setup.
I listed them for you.
ORIGINAL: asupervee72
The whole point of using these electronics was because they were laying around (free so to speak), I didn't choose them specifically for this project but i saw a possible way to make it work and i executed it. It happened to work out.
While not optimal, I'm glad you think it worked out for you. I'm not contesting the latter.... I'm only addressing the questions you posed.
ORIGINAL: asupervee72
I could buy a smaller motor and esc for the plane for nearly the same price as the gear drive and motor mount.
That's right. It may not be worth doing for THIS plane.
It's sometimes not worth it to try to make the wrong choice work... when doing it over may actually be cheaper.
ORIGINAL: asupervee72
So yes you gave advice i just don't consider it any good,
Think what you may, the numbers say what I've been telling you.
I merely pushed the figures through on your setup.
Download Motorcalc ( you can use it for the first 30 days for free ) and input the values for the motor, ESC, prop and battery pack then run an analysis on your plane... maybe the graphs will better help you understand.