Author Topic: Electric set up question (Read 4358 times)

Tom Strom · « **on:** June 17, 2012, 10:38:50 PM »

Ok, I am totally baffled. Need expert help. I built a Vector 40 and made it electric. Original set-up was with a Scorpion 3020-780 motor, Ice light 50 esc, Hubin FM-9 timer, Thunderpower 2700, 5 cell 25C batteries. RPM set at 9100, 5.3 to 5.4 sec. laps. APC 12.6EP pusher prop. I have 20 flights on the Scorpion with 4 sets of bearings.
Changed to E-Flite 25 to see if I had a problem with the firewall set up, or just a bad Scorpion motor. Set up with the E-flite motor is the same as above, except a four cell system rather than the 5 cell system. E-flight is 870 KV, so I was told to go to the 4 cell batteries. (I don't understand why yet) I have more flights on the E-flite motor than I did with the Scorpion with no bearing issues. So the airplane set up is fine. No wobble, no vibration, or any other funny things happening. That is the same with both motors.
Now, the problem. I ran the E-flite with 4 cell 2650, 35C batteries and it runs 6 minutes, no problems. I changed to Thunder Power 2700, 4 cell 65C batteries and the problems started. I can only fly between 1 min. 50 sec., and 2 min 20 sec., before motor slowly spools down and quits. Timer is still set at 6 min. flight time. Did the same thing with 3 Thunder power batteries. When I put in the 35C battery, I can go the full 6 min. again. I am only putting back 500 to 600 mah in the 2700 mah 65C battery, so it was not draining it after 2 plus minutes.

WHAT'S HAPPENING? Is the 65C discharge rate too high? I am totally lost. Please help. As you can tell, I am totally new to this electric C/L flying, but have been flying electric R/C for many years. Thanks for the help.

Tom

Tim Wescott · « **Reply #1 on:** June 17, 2012, 11:34:34 PM »

Quote from: Tom Strom on June 17, 2012, 10:38:50 PM

E-flight is 870 KV, so I was told to go to the 4 cell batteries. (I don't understand why yet)

Because the higher Kv means the motor will spin faster at the same voltage. You want the motor to have some extra speed on tap so that as the battery sags at the end of the flight the governor has enough voltage to feed to the motor to keep it spinning.

Quote from: Tom Strom on June 17, 2012, 10:38:50 PM

Now, the problem. I ran the E-flite with 4 cell 2650, 35C batteries and it runs 6 minutes, no problems. I changed to Thunder Power 2700, 4 cell 65C batteries and the problems started. I can only fly between 1 min. 50 sec., and 2 min 20 sec., before motor slowly spools down and quits. Timer is still set at 6 min. flight time. Did the same thing with 3 Thunder power batteries. When I put in the 35C battery, I can go the full 6 min. again. I am only putting back 500 to 600 mah in the 2700 mah 65C battery, so it was not draining it after 2 plus minutes.

WHAT'S HAPPENING? Is the 65C discharge rate too high? I am totally lost. Please help. As you can tell, I am totally new to this electric C/L flying, but have been flying electric R/C for many years. Thanks for the help.

No, the 65C discharge rating tells (well, should tell) you the capability of the battery, not what you're actually doing with it. If the batteries are rated honestly, a 65C battery should work better than a 35C battery.

But the "xxC" discharge ratings are pretty much a marketing game: there's no standard for what the number means -- does it mean the maximum current before the battery bursts into flame? the maximum current before you can't get one flight out of it? The maximum current before you can't get 100 flights? Nothing but a bigger number than the competition? No one knows.

If it weren't ThunderPower, I'd suspect bad batteries. Come to think of it, maybe I suspect bad batteries anyway.

Igor Burger · « **Reply #2 on:** June 18, 2012, 12:02:15 AM »

it seems to me like you have set wrong number of cell set in your ESC, or the battery has one cell less than you thing :- ))

Dennis Adamisin · « **Reply #3 on:** June 18, 2012, 05:47:16 AM »

Definitely sounds like a Lipo problem.

Have you looked at the data log from the ICE 50? I'd say look at the voltage trace, that will probably show that you have a bad cell in the offending pack(s). I guess you get to check-out ThunderPower's product support!

BTW yours is not the first problems I have heard of ont the 65C Thunderpowers, one of the EF-1 guys reported that he had 4 packs wear out after 8 cycles. They run their stuff MUCH harder than we do so I was not sure what to make of it. Norm Whittle reported here when he reached 100 cycles on his packs, by now he's probably hit 200 or more...

John Cralley · « **Reply #4 on:** June 18, 2012, 07:21:02 AM »

You are using a balancing charger --right?
You did reprogram your ESC when you switched to the 4 cell Lipo--right?
You do have the cutoff voltage set to 3.1 or 3.2 volts--right?

Hum, Dennis probably is right.

Alan Resinger · « **Reply #5 on:** June 18, 2012, 07:21:50 AM »

Tom,
Are you going to be at the Stuntathon this coming weekend? If so bring the offending gear and the good set-up and we'll figure it out for you. Make sure and bring both the good and bad batteries.
Alan Resinger

Tom Strom · « **Reply #6 on:** June 18, 2012, 10:04:08 AM »

Thanks for the replies. These are the 2700 packs I use in my EF-1 Wagner by Archie. Dennis might be right. Yes, I use a good balance charger, and all cells were at 4.19 or 4.20. All four of the Thunder Power batteries have less than 20 cycles on them. I triple checked the ESC program and it is set for 4 cell, 14.8V, 870KV. And yes, I am planning on being at Stunt-A-Thon. We will see what we can find. I am going to try again this week when the wind slows down a little, to duplicate the problem. So, thanks again for the replies. I will see you this weekend Alan. I am going to download the last eight flights from Saturday, and see what the graph says. I will let you know.

Tom

Alan Resinger · « **Reply #7 on:** June 18, 2012, 06:20:01 PM »

Tom,
See you at Thunn field. If you have a laptop with the Castle link installed bring it. Mine is on the fritz. If not someone will have one.
Alan

keith varley · « **Reply #8 on:** June 18, 2012, 07:09:07 PM »

My laptop will be there on sunday. Keith Varley

Tom Strom · « **Reply #9 on:** June 18, 2012, 08:23:31 PM »

Thanks again folks. One more question. What should the desired head speed be for my set-up? Also, I found E-flite info on the 25, 870kv motor, that is inconsistent. Brochure in the box with the motor says "slotted 12-pole outrunner design". Horizon web site lists as 14-pole slotted design. Which is it? This could make a big difference in ESC setup, yes? Again, thanks for all the help.

Tom

Dennis Adamisin · « **Reply #10 on:** June 18, 2012, 08:53:23 PM »

Count the magnets (14) Note that this would not influence why it works with one battery and not the next. However, if you were getting the WRONG RPM then this might be the culprit.

Tom Strom · « **Reply #11 on:** June 18, 2012, 10:21:58 PM »

Count the magnets. Why didn't I think of that. Dennis is just trying to make me work. I did count them and there is 14. So, on to the rest of the mystery.

Tom

William DeMauro · « **Reply #12 on:** June 19, 2012, 04:09:40 AM »

Tom,
This sounds like a bad battery. Do you store your batteries fully charged? I bet if you put a watt meter in the line it will show a fast voltage drop off.Or Like Dennis said , The Ice 50 would log it. For those of you that dont know, your batteries should NEVER EVER be kept at full charge any longer than you need too have them there. I ALWAYS put my my unused batteries back in "storage mode" after I come home from the field. I've been doing this for a year now and haven't lost 1 battery!!!
William

Darkstar1 · « **Reply #13 on:** June 19, 2012, 07:04:23 AM »

Quote from: Tom Strom on June 18, 2012, 08:23:31 PM

What should the desired head speed be for my set-up?

Tom

That depends on whether you are using set RPM or Phoenix high RPM's through the timer. If you are using the latter head speed doesn't matter. But the higher the motors kv the more RPM's you can set either way.

Tom Strom · « **Reply #14 on:** June 19, 2012, 12:18:58 PM »

Again, excellent answers. Thanks. No, I don't store them fully charged. I learned several years ago with my electric R/C stuff, to not store them charged. Had to buy new batteries all the time until someone told me how to do it right.
I have the ESC set to New Phoenix High , and set the RPM through the Hubin timer. Again, thanks to all. I am still working on the why it happened part. I will let you know what I find.

Tom

Peter Ferguson · « **Reply #15 on:** June 27, 2012, 05:51:10 PM »

Keith, you laptop might have ben there but there was no sign of you, unless you have significantly changed your appearance. Tom what was wrong?

Tim Wescott · « **Reply #16 on:** June 27, 2012, 08:39:20 PM »

Quote from: William DeMauro on June 19, 2012, 04:09:40 AM

I ALWAYS put my my unused batteries back in "storage mode" after I come home from the field. I've been doing this for a year now and haven't lost 1 battery!!!

Have you noticed how irritating it is to be telling someone to always change their oil, or sweep the moss off their roof, or some other good-maintenance thing like that, then have some slob come by and mention that he hasn't changed his oil for 100000 miles and his car runs fine?

If I don't fully charge my batteries at the field before I go home, I leave them uncharged for days or weeks, then fully charge them and put them away. And they're Turnigy. I've had three of them for about three years now, I've been trying to kill them with neglect, and they're all going strong.

Tom Strom · « **Reply #17 on:** June 28, 2012, 02:34:00 AM »

Well, Friday before Stunt-A-Thon, I drug my wife to the field to help me find the problem. Now, those of you who do not know me or my wife, I will tell you she probably knows about as much as I do on the modeling thing. And yes, she even painted one of my aircraft for me while I was busy building another. ( Did not have the heart to tell her the color was, well, not quite what I had in mind. PURPLE)

Anyway, I put the battery in the Vector, and she launched it. About 2 min. into the flight, I heard her ask, (nice thing about electric) "can you hear it slowing down"? And I replied, No, can you? She said "yes, but not by much. It has a different pitch". One minute later it quit. Well, after a few choice words, and my being ready to throw everything in the car and head home, she says, "what can we change to fix it?" Well, why didn't I think of that. So, I proceeded to remove the ESC, and put one of the back-up ones in. Loaded up on queertrons, pushed the button, and flew. Flew the whole pattern. Not very well, but I flew the whole pattern. Ok, let's put the third ESC in and see what happens. Same thing as the second one. It flew!!! 5 min. 45 sec. Exactly like it was supposed to. So, let's put the first one back in. Guess what? Flight lasted 1 min. 22 sec. Well I'll be. Must be a bad ESC. Put back-up number two back in, and lew 5 min. 45 sec. WHOLE PATTERN AGAIN.

She just smiled, said "now was that so hard?" Everything worked just like it was supposed to at the contest also. So, now I can stop worrying about the flight time problem, and start practicing. (sent the ESC back to Castle for an eval. Castle ICE Lite 50.)

Tom
(with help from Lois)

bob branch · « **Reply #18 on:** June 28, 2012, 05:58:24 PM »

Way to go Lois! I didn't know we could have flight engineers in stunt. Maybe gota get me one of those!

bob branch

Peter Ferguson · « **Reply #19 on:** June 30, 2012, 11:56:57 PM »

Nice to have expert help close by. Good job Lois! Now she can critique your flying.

bob branch · « **Reply #20 on:** July 01, 2012, 06:56:26 AM »

Peter

Not sure that would be good for a marriage.

bob branch