Brushless ESC Timing

[JayCee]

Hi Tom

 

<I see the motor spec calls for good quality 85a esc?>

 

Which brings me back to my problem, why at full throttle am I only drawing 42 amps?

 

If I was drawing what I expected approximately 60 amps then my watts in would be about 1800 watts which would be about right!

 

I have ruled out battery, tried two different sets the voltage drop on full load is only 2.52 volts

I have ruled out poor connections, although there are quite a few with the series leads etc. but they are all 4mm bullet or Deans  with good solid connections.

 

So I guess it's either ESC, ESC timing or Motor...bit of a mystery.

 

JC

 

Edited By JayCee on 19/02/2011 17:04:56

[Tim Mackey]

I meant which motor are you using NOW

[Tom Wright 2]

JC I suppose you try a slightly larger prop and see if the current goes up without any motor / esc over heating.

[JayCee]

Sorry Tim

 

This One

 

JC

[JayCee]

Tom

 

I could try that as a bench test (If I had one) but in practice 17 inch is the max I can swing without the prop grounding when the tail lifts!

 

JC

[Tom Wright 2]

Ahh the g110 has a max current rating of 55a could you have over cooked it on previous flights?

[JayCee]

Don't think it's likely Tom flat out I'm only drawing 42 amps

 

JC

[Tom Wright 2]

JC Yes you are now but if you did over cook something during previous flights ,the resistance must have gone up somewhere ,to reduce the current by 20a or so, and if no other factors have been changed by you,it does raise the timing issue as an on going question, or an increase in system resistance .

 Sorry its going full circle a bit but we do our best  .

TW2.

Edited By tom wright 2 on 19/02/2011 17:51:44

[Tim Mackey]

Its allegedly rated for 55A constant with 65A burst - and if your initial wattage was 1800 thats around 64A so getting pretty close to max. It could be that it has overheated, and the magnets have cooked - the maximum power is claimed to be 1797 which is a bit of an odd figure

[Tom Wright 2]

Yes Tim that's what i was getting at.

[JayCee]

Hi Tom & Tim

 

Yes I see where you are coming from and I do appreciate all of the help and advice, the plane has only had three flights in total and the low power issue was noted on its maiden flight.

 

The maiden flight was taken by our resident 'Test Pilot' Joking apart he is one of the most experienced pilots at our club and we all turn to him to take up and trim a new model. The first thing he said was that he was surprised that it appeared underpowered for a aircraft running on 8 cells...and that is where it all started.

 

A bench test gave a reading of 1400 watts initially, I did have one test at 1800watts for some reason and now it's down to just over 1300watts it's different every time!

 

The first thing you think of is bad 'High Resistance' connections but I have checked and double checked The batteries have Deans As I like to keep every thing universal but the series lead terminates in 4mm bullets

 

 

The reason for the bullet connectors is that the ESC has a thin black lead that is connected first to eliminate the 'Spark' I obviously couldn't do that withe Deans as it's + first followed by thin black followed by thick black! As you can see the cable size is correct and the connections secure..............still a mystery!

 

JC

Edited By JayCee on 19/02/2011 18:44:55

[Tim Mackey]

Al looks good to me JC - as you say, a bit of a mystery, and I guess the only wqay forward now is the good 'ol process of elimination.

Dont suppose you / a friend has another ESC that could be tried on the motor etc?

Its looking like you are narrowing things down to Motor or ESC.

[JayCee]

Thanks Tim

 

Sorry mate must be driving you all up the wall with this

 

The ESC is HV because of the 8 cells and is as rare a Rocking Horse deposits as far as friends and club members are concerned............I'm the only one flying big leccy stuff.

 

The new E-Flite motor should be here Tuesday and hopefully a compatible programming card if ' Robotbirds' have them in stock so I guess I start there......thanks once again for all your help, will keep you posted on developments.

 

JC

[GONZO]

Just a thought, as well as all your wiring, soldering and connections have you checked the bullet connectors(and the wire - partially fractured??) on the three wires coming from the motor. Sometimes the quality of the soldering of these by the manufacturers is less than satisfactory.

[JayCee]

Hi Gonzo

 

Glad your still bearing with me

 

Not sure if you picked it up in the posts the motor I am using at present is a Chinese Clone (Turnigy) which is why I always had my suspicions.

 

It didn't come pre wired with bullets I put them on, and the three wires are just extensions of the motor windings so no other connections.

 

I think Tim is right it's either Motor, ESC timing or the ESC

 

Once the new E-Flight motor arrives and hopefully the card from Robotbirds I can do the first two and keep my fingers crossed.

 

It's worth spending a bit of time and money the plane a beauty....what do you think?

 

 

 

JC

 

Edited By JayCee on 19/02/2011 21:52:57

Edited By JayCee on 19/02/2011 21:54:51

[PatMc]

If it was the motor or esc timing you would get the same watt/current reading with the same load & battery voltage but you have observed different power input readings.

If it was high resistance anywhere it would be easily detectable as a hot spot (42^2*R watts) .

If it was magnets losing power the current & watts would increase.

 

Have you checked the throttle range settings or is there any chance that you' may have inadvertently re-set them at some point ?

Wrong settings here would explain changing Watt reading at full throttle as the esc could interpret full stick as part throttle.

 

Another less likely explanation is that when the battery is plugged in the esc "thinks" it's detecting more than 8 cells & reducing power to stay within the LVC for that number of cells.

 

[Tom Wright 2]

Hi JC Unless we here you have solved the problem,and if you do want to pull 1800w through a significant part of future flights,i would consider fitting a larger motor and ESC.

This would give safe margins and maybe help to keep that very nice model ,at safe flying speeds.

TW2

[Tim Mackey]

I cant see the last paragraph being applicable - surely if it was incorrectly detecting the cell count, the only thing that would be affected would be the actual LVC threshold ? - its not going to affect the general power delivery of the ESC.

If it "detected" say 10 cells instead of 8, then it would expect a nominal voltage of around say 35V, and would probably set the LVC to kick in at about 28.5.

The 8 cells would be giving around 28V fresh off the cooker ( under load ) so the LVC would be effective immediately, and the motor would not even run past a second or two.

I thought I had read that the motor was actually running - and indeed the model was flown, but the power has been dropping off ever since the first flight or so

[Tom Wright 2]

Hi Pat yet another bit of lateral thinking nice one.We Dont give up JC ,confound us all and come up with the answer no ones thought of yet.By the way did you check the throttle setting?

TW2.

Edited By tom wright 2 on 20/02/2011 15:44:21

[PatMc]

Posted by Tim Mackey - Administrator on 20/02/2011 15:33:06:

I cant see the last paragraph being applicable - surely if it was incorrectly detecting the cell count, the only thing that would be affected would be the actual LVC threshold ? - its not going to affect the general power delivery of the ESC.

If it "detected" say 10 cells instead of 8, then it would expect a nominal voltage of around say 35V, and would probably set the LVC to kick in at about 28.5.

The 8 cells would be giving around 28V fresh off the cooker ( under load ) so the LVC would be effective immediately, and the motor would not even run past a second or two.

I thought I had read that the motor was actually running - and indeed the model was flown, but the power has been dropping off ever since the first flight or so

I agree that the LVC scenario is a long shot, which is why I said it was a less likely explanation. When connecting the initial voltage spiking can sometimes fool the auto detect of the esc . JayCee has already said that unloaded he battery showed 33.5v & full load was 30.98v. The default LVC for this esc is 3v/cell & brake off so it's just possible it's detecting 10cells & reducing the power to maintain the voltage at above 30v.

 

I think the throttle range setting is a strong suspect. Even if it had been set initially it would be easy to switch the Tx on at part throttle before the esc was connected then after a couple of seconds wonder what the beeping was & close the throttle not realising that a new range setting had been established.

[Tim Mackey]

Now this is where I am getting confused.

I dont believe an ESC "reduces power to maintain a particular detected voltage".

AFAIK, it just delivers full power ( at WOT ) until the LVC voltage is detected, at which point it either shuts off motor power, or reduces, or pulses it - depending on the model and settings chosen.

The throttle range detection is a possibility I guess - have you tried retraining the ESC with the correct throws JC?

Edited By Tim Mackey - Administrator on 20/02/2011 16:56:37

[Tim Mackey]

Incidentally, I do believe this model can be user set to "beep" count the number of cells detected at boot up - maybe this should be deployed too JC? It requires a user setting and therefore you ideally need the program card that you have - I believe, ordered.

[JayCee]

Firstly, everybody a big thank you for all you input.

 

Sorry for the delay in responding, today I indulged in my other hobby Golf! got wet on the course and when I got home even wetter as something had sprung a leak in my newly installed Bathroom

 

Have only just finished cleaning up the mess, and said goodbye to the plumber, got a cup of tea and some toast come to the PC............and Wow you have all been busy!

 

It never ceases to amaze me the the amount of help and support I have received from you all in the modeling flying forums since I joined last year...Thank You

 

Right back to the posts, I have to be honest some of it has gone over my head LVC thresholds, cell counts....help!!

 

Now I have been fortified with tea and toast I am going to check the throttle setting again, obviously it was the first thing I set initially but as you say the Tx could have been switched on with the throttle stick not on minimum it is strange the the watts input is never the same twice

 

I know I have jumped the gun a bit ordering a replacement motor and your technical thinking is that it is an unlikely suspect, it's just that it was the only 'cheapie' bit of kit in the power train and I just jumped to that conclusion.

 

Will post results later

 

JC

 

 

[JayCee]

OK

 

Just ran everything up again, reset the throttle that's not the problem ( I would have felt and idiot if it had just been that  

 

Readings today Voltage  33.07 Amps42.98 Watts 1344.8

 

JC

Edited By JayCee on 20/02/2011 18:28:20

[PatMc]

Posted by Tim Mackey - Administrator on 20/02/2011 16:56:00:

Now this is where I am getting confused.

I dont believe an ESC "reduces power to maintain a particular detected voltage".

AFAIK, it just delivers full power ( at WOT ) until the LVC voltage is detected, at which point it either shuts off motor power, or reduces, or pulses it - depending on the model and settings chosen.

The throttle range detection is a possibility I guess - have you tried retraining the ESC with the correct throws JC?

Edited By Tim Mackey - Administrator on 20/02/2011 16:56:37

I don't want to labour the LVC possibility as I think it's probably a red herring in this case. I must admit I've never run a lipo battery down that far & it's along time since I used nickel cells so can't remember what happened with them at LVC.

I agree that full power will be delivered until LVC but the hypothesis is that LVC is more or less immediately albeit wrongly detected (30v).

The default is for the ESC to gradually reduce power which will cause the voltage will rise just above LVC (30.98v). To my mind the logical programming will now keep the rate of power reduction just on the LVC threshold which will have the effect of maintaining the voltage above 3v/cell whilst reducing the power available. The alternative would be gradually reducing power regardless of the battery recovering which would seem an unnecessarily fixed outcome.

 

Yes, the esc beeps out the number of cells detected when the battery is connected. It does this every time during it's pre-arm checks & doesn't require any change to user settings.