Thread Tools
Nov 14, 2019, 05:20 PM
Registered User
Thread OP
Discussion

Power system not functioning correctly


Hi Guys

I have a foamie that I bought from a guy. It has a 950 kV Turnigy outrunner motor and a 30A hobby king ESC. I am using 3S 1000mA packs. Initially it went OK but now what happens is that it initially goes to full power then within about 5 seconds drops back to about half power. This happens with different battery packs all freshly charged and check out OK . Any ideas?

Don
Sign up now
to remove ads between posts
Nov 14, 2019, 08:29 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
What is the C-rating of your 1000mAh 3S batteries ? It's possible the batteries are not capable of delivering the amps drawn by the motor at full throttle .
Nov 14, 2019, 09:53 PM
Keep Flying Model Aeroplanes
Rhea's Avatar
A Watt meter would be a helpful tool for you but my guess is that the magnets have been overheated and they are no good.
Nov 14, 2019, 10:20 PM
Wake up, feel pulse, be happy!
Piece's Avatar
No mention of prop size?
Latest blog entry: Jeti ESC resto-mod
Nov 14, 2019, 11:23 PM
If it flies, I can crash it.
rocketsled666's Avatar
Quote:
it initially goes to full power then within about 5 seconds drops back to about half power
Meaning: If you go to full throttle it goes fast for about 5 seconds and then slows down to a lower RPM? How do you know it's about 1/2 power?
Nov 15, 2019, 01:03 AM
Registered User
Thread OP
Hi Iím new to electric but have flown for about 40 years. The prop is 10 x 3.8. Packs are nanotech 25 - 50C. Donít have a watt meter. Regarding power it is just less by a sufficient amount to make the plane unflyable.
Nov 15, 2019, 01:17 AM
If it flies, I can crash it.
rocketsled666's Avatar
A 10x3.8 on a 950KV motor and 3S isn't going to generate a lot of forward speed. If the power you're getting is less by a small amount and that makes the plane unflyable, it suggests you really didn't have enough power to begin with. What is the airplane this is in? Size/weight?

Also, I don't have anything good to say about Nanotech cells. Tried 'em once, didn't have a good experience. Never tried again. I would guess your problem is that your packs are tired. They'll still appear to charge just fine, but under load they produce less voltage because their internal resistance is higher.

But I bet if you went to something like an 8x6 the plane would fly better with the existing batteries.
Nov 15, 2019, 01:50 AM
Wake up, feel pulse, be happy!
Piece's Avatar
It's hard to tell what kind of plane it is from the photos, but the setup is well-matched in terms of prop, motor, and battery for a 3D foamie, or maybe a floaty trainer. It would be pretty anemic in anything that needs more pitchspeed than a basic park flyer.

In any case, no matter what it's attached to, you'd almost have to try to have less than 1:1 thrust-to-weight on a setup like that. If it's not pulling stumps, something is wrong. None of the components should be overworked in that system, so the behavior sounds like a battery issue. Even a freshly charged battery can perform like crap if the cells have been abused.

It's hard to overstate the usefulness of a wattmeter
Latest blog entry: Jeti ESC resto-mod
Nov 15, 2019, 10:28 AM
Registered User
Mikkels
A Turnigy 2836/9 is quite a powerful motor so with a 10x3.8 it will work your 1000 mAh 3s batteries fairly hard.
The fact it worked to start with but now slows down does suggest the most likely cause is the batteries are now simply running out of power.
Bear in mind that LiPo are very sensitive to over discharge. Discharge to below 3V per cell (the motor slows down to half speed at full power!) and the LiPo is likely to be permanently damaged usually loosing capacity. The result is it then runs out even quicker and does still more damage when it does .

What sort of charger are you using? Does it show the individual cell voltages whilst charging and what are the cell voltages when fully charged.
Nov 15, 2019, 12:24 PM
Bombs away! Err...landing
Ira NZ's Avatar
Quote:
Originally Posted by Mikkels
Don’t have a watt meter.
Get one.
Trying to do...Well...Anything with an electric setup without one is like trying to figure out "Why is my fence crooked and falling over?" without a level or even a measuring tape.
Nov 17, 2019, 10:00 AM
Sure, I can fly after sunset!?
Quote:
Originally Posted by balsa or carbon
What is the C-rating of your 1000mAh 3S batteries ? It's possible the batteries are not capable of delivering the amps drawn by the motor at full throttle .
I had this happen with my first plane. Was fine for a long time and one day the motor cut out on full throttle takeoff. At first, I could control this using less throttle but soon it wouldnít fly. Put brand new battery in and it worked.
Nov 18, 2019, 01:45 AM
Registered User
Thread OP
Quote:
Originally Posted by mybad
I had this happen with my first plane. Was fine for a long time and one day the motor cut out on full throttle takeoff. At first, I could control this using less throttle but soon it wouldnít fly. Put brand new battery in and it worked.
I have aa couple of 3S 2200 cells which are working well on another plane. PA Addiction. I will try one of those on the foamy and see if the symptoms persist. Thanks for the tip.
Nov 18, 2019, 01:47 AM
Registered User
Thread OP
Quote:
Originally Posted by Quorneng
Mikkels
A Turnigy 2836/9 is quite a powerful motor so with a 10x3.8 it will work your 1000 mAh 3s batteries fairly hard.
The fact it worked to start with but now slows down does suggest the most likely cause is the batteries are now simply running out of power.
Bear in mind that LiPo are very sensitive to over discharge. Discharge to below 3V per cell (the motor slows down to half speed at full power!) and the LiPo is likely to be permanently damaged usually loosing capacity. The result is it then runs out even quicker and does still more damage when it does .

What sort of charger are you using? Does it show the individual cell voltages whilst charging and what are the cell voltages when fully charged.
I have a balancing charger and the cells seem to all charge to a total voltage compatible with full charge.
Nov 18, 2019, 01:51 AM
Registered User
Thread OP
Quote:
Originally Posted by Piece
It's hard to tell what kind of plane it is from the photos, but the setup is well-matched in terms of prop, motor, and battery for a 3D foamie, or maybe a floaty trainer. It would be pretty anemic in anything that needs more pitchspeed than a basic park flyer.

In any case, no matter what it's attached to, you'd almost have to try to have less than 1:1 thrust-to-weight on a setup like that. If it's not pulling stumps, something is wrong. None of the components should be overworked in that system, so the behavior sounds like a battery issue. Even a freshly charged battery can perform like crap if the cells have been abused.

It's hard to overstate the usefulness of a wattmeter
It is a foam Extra of about 40 inch span. Used to fly well. Now not enough power to launch after initial surge. I soldered the power leads to the engine to ensure contact is good. That was OK for a while then after a winter layover the problem occurred. Happens with both packs I have for the plane but have not tried the other packs I have.
Nov 18, 2019, 01:53 AM
Registered User
Thread OP
Quote:
Originally Posted by rocketsled666
A 10x3.8 on a 950KV motor and 3S isn't going to generate a lot of forward speed. If the power you're getting is less by a small amount and that makes the plane unflyable, it suggests you really didn't have enough power to begin with. What is the airplane this is in? Size/weight?

Also, I don't have anything good to say about Nanotech cells. Tried 'em once, didn't have a good experience. Never tried again. I would guess your problem is that your packs are tired. They'll still appear to charge just fine, but under load they produce less voltage because their internal resistance is higher.

But I bet if you went to something like an 8x6 the plane would fly better with the existing batteries.
I will try a smaller prop. I donít really understand how you match props with power set ups


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Help! Correct power system before maiden flight?? tmec Power Systems 7 Oct 08, 2017 11:32 AM
Question Not sure if this is a correct post or not BillKuhn Fuel Heli Talk 0 Jun 12, 2016 06:10 PM
Question is this power system functional Zeyad metwaly Power Systems 1 May 31, 2016 04:56 AM
Discussion Brake function not working on Thunder Power ESC PsychoPilot Power Systems 7 Feb 01, 2010 01:49 AM
Question 8UAFs - "Link" function not working correctly in PMIX Andy W Electric Plane Talk 14 Aug 05, 2004 07:32 PM