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Steve
12-23-2006, 05:39 PM
I've recently changed some servos on my Slow Stick and reconfigured my CC25 ESC, but now it will only go to 1/2 throttle...about 4.5A. Even when I push the stick all the way up, there is no change in RPM beyond 1/2 stick. I'm using a 3C lipo and it shows 11V so that's not the problem. I re-configured the ESC twice and used the "auto detect" for full throttle setting. What's the problem?

Larry3215
12-24-2006, 05:40 AM
Try going to "fixed throttle" instead of auto detect.

Then lower the end point on ch 3 untill you get full throttle at full stick travel. On most of my Rx's this is around 55% - 65% but some are higher.

Here is how I do it.

1)I disconect the motor from the esc - you could probably remove the prop and be fine also. Do this so you dont have a plane running at full throttle over and over.
2)Make sure you can see the LED on the esc.
2A)set the throttle trim to center on the TX
3)Conect the battery and arm the esc.
4)go to max stick travel and see if/when the LED turns on. When the LED lights up the esc is at full power.
5) lower the end point on the TX untill the LED turns on just before max stick movement.
6)If the LED is not comming on - then you need to INCREASE the end point on the TX untill it does come on at full stick travel.

To set the lower end point:
1)power down the esc then re-conect the motor - leave the prop off.
2)leave the throttle stick all the way down and slowly decrease the end point on ch3 untill the motor begins to start then back off a bit. I like my motors to start about 2 clicks up from the bottom.

If you do this you will have the max usable stick travel for throttle and no worries about auto detect getting it wrong. You also dont have to run the plane up to full power for 4 seconds before every flight to "set" the throttle end points each time.

You need to do this for each different Rx you use. they all end up having slightly different settings needed.

Good luck!

Larry

Steve
12-25-2006, 01:17 AM
Thanks for the xmas present larry! I'll give it a go tomorrow and let you know how it worked out.

Joe Ford
12-26-2006, 12:22 AM
Let me know what you find Steve.

Steve
12-26-2006, 12:42 PM
Going to "fixed throttle" definitely helped, but after flying for a while, the ESC begins to limit the voltage to about 1/2 throttle and stays there. What setting on the ESC would create that effect?

Larry3215
12-26-2006, 05:05 PM
That sounds like the low voltage cutoff. Your packs have gotten down to the cut off voltage - what ever that is set to.

Larry

Steve
12-26-2006, 05:13 PM
I thought I had everything set up correctly. Do you think it's safe to set the lv cutoff at 9V for a 3c lipo?

Joe Ford
01-03-2007, 04:10 AM
Steve...9v is the standard cutoff voltage for 3 cell lipos. :) 3v/cell

Steve
01-03-2007, 11:37 AM
Yes, I get that. But what I don't get is why the voltage drops while the heli is in flight causing the ESC to switch to LVC mode. Is that a function of the ESC? IF I disabled current sensitivity, would that help?

Joe Ford
01-05-2007, 01:53 AM
No it wouldn't help. The LVC is to protect your battery. If you set the controller to hard cutoff you'll know if it's the LVC kicking in or not. In hard cutoff mode the motor will simply shut down. If it still runs at 1/2 throttle it's something else. Any idea what motor you're running and what software you have on the controller? If it's an outrunner try low advance timing. If that doesn't solve it the problem is most likely receiver interference...ESC's are slaves to the receiver...they only do what they're told.

Steve
01-06-2007, 03:51 PM
Set up is Himax 2025 with a 6:1 gear and 12x6 prop. Battery is a 2100 3s lipo. No idea about the software on the ESC. You guys don't (or at least didn't when I purchased my ESC's) identify your products well so I don't have a clue. I run a Mac household, so I can't take advantage of any software controls. I'll try your suggestions and see what happens.

Larry3215
01-06-2007, 05:34 PM
Steve, you mentioned in your first post that the lipo voltage was 11 volts. Is that 11 volts just sitting on the bench or is that 11 volts while the motor is running at full throttle with the prop on?

If your battery is at 11 volts just sitting on the bench not conected to anything its, its completely discharged. Thats 3.66 volts per cell and there is no usable capacity left below 3.7 volts per cell - resting voltage.

If it is 11 volts under full load, thats not bad. The pack is handling the load fairly well.

Once the motor begins to slow down, try measuring the voltage under load and the resting voltage again. that should tell us something.

Larry

Steve
01-06-2007, 08:01 PM
I thought a 3 cell lipo was ok to discharge down to 9.3V (3.1V/cell resting) without any problems, so if my resting voltage was 11.47V my little brain tells me that there is still some capacity there to be used. Am I wrong about that?

When the motor slows down it's a function of the esc detecting running voltage dropping below 9V so it switches into LVC mode which then will not allow voltage to exceed 9V regardless of throttle setting. Seems like it then runs at about 40% throttle. At that point, when I measure the resting voltage it is 11.47V.

My cells are about 2 years old and I'm not sure how many cycles I have on them at this point. I don't think it's any where near 100.

How can I test them to assess their current condition?

I have a wattmeter.

jdewolftx
01-24-2007, 02:57 PM
I have an eFlite Park 480 (1020 kv version) that is running with an APC 10X7e prop. I have similar cutoff issues and when I program the cutoff to soft it then does the revving phenomenon that you described.

I suspected the battery (Dual Sky 2100 3s) but I have tried two other batteries including a DV 3s 2100 from one of my buddies who has always kept it in good balance. They all did the same thing. The watt meter shows that the motor is never able to unwind as it is causing too big a drop in voltage. The system is using a CC25 that is current on its software.

I haven't tried the timing, but I will. The interference is an interesting thought but this clearly looks to be something circuit related (not just an intermittant hit from a radio source).

Could it be a bad motor? Could it be a bad speedcontroller?

This is quite frustrating.

-Jeff

Steve
01-24-2007, 03:24 PM
yes....frustrating. I'm thinking now that the C rating of the lipo's that I'm using just aren't up to the peak amp/V draw of my motor/prop combo. I get about 5-6 min of flight at WOT and everything is normal, but then at some point when I give it more throttle it shifts in to LVC mode and will only give me about 50% power.

What is the C rating of your battery and what is your amp draw WOT?

jdewolftx
01-24-2007, 05:56 PM
I think you are right about the ratings. I heard that last year many manufacturers were claiming 20C when it was really only around 15. However, when I have it on the watt meter it seems that the current never gets very high (18 amps). I thought that voltage lags current in lipo discharge. This is why it is very confusing to me why I get a voltage cutoff before an overcurrent situation.

-Jeff

jdewolftx
01-25-2007, 03:57 PM
After an hour of troubleshooting at the hobby shop, we narrowed it down to a short in the ground wire that goes from the SC to the receiver. All that pulling it out and pushing it in. Once we changed that, the oscillation went away. Just to be safe, I modified the lower cutoff to 8.6 volts. I have the USB connector so I can easily do this.

Good luck with your troubleshooting!

PS. With an 11X7E, eFLIGHT 480 1050keV motor and a 12C 2250 MaH battery, the system was running 180 watts at 22 amps. and around 10 volts! Well within the CC25 limits.