I have my second Ice 75 set up on a 500 sized UH-1N scale heli. I have been having some problems trying to get the heli flying smoothly with a SK720, and today tried a couple of flights with the electronics powered using a 2s A123 battery instead of the internal BEC. I noticed that on the Skookum log, the voltage seemed to be fluctuating between 5.5V and 6.0V with the internal BEC set to 6.0V and thought that this might be affecting the Skookum's performance, hence the trials.

In the attached log file, the first two flights are using the A123 battery and were mostly flying scale circuits.

The second two flights were using the internal BEC set to 6.5V, almost all of it hovering in wind.

What I don't get is the following;

1. The first pair of flights shows signifcantly higher power and amp readings, and shows around 3.85Ah out of the 5000mAh lipo. My Hyperion Duo II actually put back 3644mAh.

2. The second pair of flights shows much lower power and amp readings, and only 2.4Ah out of the 5000mAh lipo. My Duo II actually put back 3814mAh.

3. So, I know that the mAh reading in the logs has never been accurate, but why would the log show much higher power and amps on the first two flights when they were doing circuits which is usually about 10-15% less power than just hovering. The actual mAh confirms that the two hovering flights used more power than the two circuit flights, but looking at the logs the first two flights averaged about 520W, whereas the 3rd & 4th flights averaged about 340W.

Any thoughts ?

Cheers
Colin

You should post a graphic of the log. I don't like downloading zip files, they may contain surprises!

Ok, but that being said, although the current measurements have only so-so accuracy, they should be quite good as comparisons between different flights with the same ESC.

Also recall that power and energy are two different things. Power is the instantaneous use of energy per unit of time. The log is showing you power. However the energy you put back into a battery is a function of how much power you were using AND how long you were using it. In other words flying a long time at low power can use up more energy than a short high power flight.

Finally, power is the product of current times voltage. A poor battery with sagging voltage will need more current to make the same power. You could drag a poor battery down more than a good battery. When you go back to charge the pack, your charger is Just telling you how much charge it put back.

Alan

Thanks for the response. Here is the screen shot. I posted the file (and had to zip it) so that some of the experts here can get more detail if required. I sometime find it hard to get anything more than an overall impression from a screen shot.

As you can see from the image, the two lipos (2 flights from each) behaved in a very similar way and the both ended the flight with a minimum voltage of 22.1V, so it was not a case of the first one sagging more than the other.

Almost the entire first two flights were higher than the entire second two flights, so it is not a case of peaky loads. The first two flights were gentle scale circuits, and the second two were steady hovering, so neither had dramatic collective changes.

If you (and others) could please take a look at the posted image and comment, I would appreciate it.

Cheers
Colin

Well that is a seriously strange plot.

As you say, the power and current during the second set of flights is way down, yet the ESC temperature is much hotter, reaching 80C (or 176 F) which is pretty hot I believe. I am guessing this extra heat is coming from the BEC being used for these two last flights, so I think I'd be worried that your servo system is drawing too much current from the internal BEC.

I note that power is calculated from the current and voltage, so if the current sensor is off, then the power (volts*amps) and Amp-hours (amps * time) plots will also be off.

I don't know if the high BEC draw and heat are affecting the current measurement in the ESC---it shouldn't I think.

Probably worth while talking to CC.

Alan

I am glad I am not the only one who thinks it looks strange. I think that at least some of the temps in the last two flights is because I was hovering in direct sunlight in 35°C / 95°F weather, whereas the first two were a bit earlier (maybe 30°C/86°F) and doing FF circuits (so a bit of airflow).

There may also be some temp coming from the BEC - I have 3x Futaba 9650 cyclic servos and a Futaba BLS 451 on the tail. The servos should not be working too hard hovering a scale 500 at 1900rpm though I wouldn't think.

I will give it a couple of days in the hope that Clint or one of the Castle guys reads this, if not, I will send it to them for comment.

Cheers
Colin

Originally Posted by Andy01

Alan

I am glad I am not the only one who thinks it looks strange. I think that at least some of the temps in the last two flights is because I was hovering in direct sunlight in 35°C / 95°F weather, whereas the first two were a bit earlier (maybe 30°C/86°F) and doing FF circuits (so a bit of airflow).

There may also be some temp coming from the BEC - I have 3x Futaba 9650 cyclic servos and a Futaba BLS 451 on the tail. The servos should not be working too hard hovering a scale 500 at 1900rpm though I wouldn't think.

I will give it a couple of days in the hope that Clint or one of the Castle guys reads this, if not, I will send it to them for comment.

Cheers
Colin

Colin we are at HHAEFI this week. I took a quick look at the graphs and noticed 2 graphs started around 23 volts and 2 started at 25 volts... Not sure why they are different... I would say to repeat the testing and mix up the batteries... I wish I could add more info...

With such a low amp draw the current and the amp hours may not be super accurate...

Clint

Thanks - I knew you would be around somewhere

The reason that the 1st and 3rd flights are at 25V and the 2nd and 4th flights are lower is because I get two flights per lipo, so the second flight always starts lower than the first.

I am running a 6s 5000mAh lipo because the scale fuselage is tail heavy, so the ballast may as well be useful , so it has enough capacity for two 5 minute flights.

I do appreciate that the result may not be dead accurate, but I have been 5 different Ice and Ice HV ESCs (Ice 50, 2x Ice 75 & 2x Ice2 80HV) all at low amp draws in scale flying for a few years, and this is the first time I have seen a weird discrepancy like this.

I am happy to try again, but my concern was that this may be a symptom of a faulty ESC. The last thing I need is a scale heli taking a dirt nap because the ESC died in flight after giving some sort of warning sign.

I would appreciate any further advice you may have once you get some spare time.

Cheers
Colin

Originally Posted by Andy01

Clint

Thanks - I knew you would be around somewhere

The reason that the 1st and 3rd flights are at 25V and the 2nd and 4th flights are lower is because I get two flights per lipo, so the second flight always starts lower than the first.

I am running a 6s 5000mAh lipo because the scale fuselage is tail heavy, so the ballast may as well be useful , so it has enough capacity for two 5 minute flights.

I do appreciate that the result may not be dead accurate, but I have been 5 different Ice and Ice HV ESCs (Ice 50, 2x Ice 75 & 2x Ice2 80HV) all at low amp draws in scale flying for a few years, and this is the first time I have seen a weird discrepancy like this.

I am happy to try again, but my concern was that this may be a symptom of a faulty ESC. The last thing I need is a scale heli taking a dirt nap because the ESC died in flight after giving some sort of warning sign.

I would appreciate any further advice you may have once you get some spare time.

Cheers
Colin

You may want to make sure the auto lipo detection is turned off and you set the LVC your self.... Count the cells on the second flight and it may not be correct which could cause different issues....

Clint

Thanks. Already done that.

The problem was not just with the second flight on each lipo. The first lipo read very high on both flights, and the second lipo read very low on both flights.

Cheers
Colin

It would be interesting to see what the current does if you use the receiver pack again. I'd also assume the temp would drop back down.

OK, an update with lots more data.

I flew 8 flights today, and did large scale circuits for all of them. I used four 6s 5000mAh lipos, and did two flights on each lipo (First log (Flights 36-39) is Lipo1 & 2 and second log (Flights 40-43) is Lipo3 & 4).

Lipo 1
Two 5 minute flights, internal BEC set to 6.5V, average power = ± 280-300W and average current = 12-13A. mAh according to log = 2290mAh, mAh according to Hyperion Duo II = 3586mAh, logged temp = 62°C (37°C above ambient) with about 5°C of this climbing during a short hover at the end of flights. Lipo voltage at 25.2V at start, 23.0V at end of first flight, and 22.2V at end of second flight.

Lipo 2
Two 5 minute flights, internal BEC set to 6.5V, average power = ± 260-320W and average current = 11-14A. mAh according to log = 2340mAh, mAh according to Hyperion Duo II = 3565mAh, logged temp = 67°C (39°C above ambient) with about 5°C of this climbing during a short hover at the end of flights. Lipo voltage at 25.2V at start, 23.1V at end of first flight, and 22.2V at end of second flight.

Lipo 3
Two 5 minute flights, internal BEC set to 6.5V, average power = ± 250-340W and average current = 11-14A. mAh according to log = 2200mAh, mAh according to Hyperion Duo II = 3363mAh, logged temp = 65°C (37°C above ambient) with about 5°C of this climbing during a short hover at the end of flights. Lipo voltage at 25.2V at start, 23.1V at end of first flight, and 22.2V at end of second flight.

Lipo 4
Two 5 minute flights, internal BEC disconnected (red wire out) & electronics power from fully charge 2s A123 (about 6.6V), average power = ± 440-540W and average current = 21-23A. mAh according to log = 3910mAh, mAh according to Hyperion Duo II = 3655mAh, logged temp = 67°C (39°C above ambient) with about 5°C of this climbing during a short hover at the end of flights. Lipo voltage at 25.2V at start, 23.1V at end of first flight, and 22.2V at end of second flight.

and for comparison I have included a third log graph (Flights 28-31) from when I was running the internal BEC at 6.0V,

Two 5 minute flights, internal BEC set to 6.0V, average power = ± 300-400W and average current = 13-17A. mAh according to log = 2510mAh, mAh according to Hyperion Duo II = 3585mAh, logged temp = 66°C (41°C above ambient) with about 5°C of this climbing during a short hover at the end of flights. Lipo voltage at 25.2V at start, 23.1V at end of first flight, and 22.2V at end of second flight.

So, the conclusion from this seems to be that the higher the BEC voltage the lower the logged power & amps;

- no BEC use = very "high" power of 500W (average),
- 6.0V BEC = 350W (average) and
- 6.5V BEC = 300W.

In general my scale circuits here were very similar and usually produce almost identical results on the logs and power usage, and this is backed up by the fairly consistent mAh put back in by the charger (between 3363mAh and 3655mAh, but mostly between 3565mAh and 3655mAh) and the very consistent voltages at start, middle and end of these lipos. The other thing to note is that the mAh is fairly consistently too low (by a large margin with the BEC in use).

It appears that logging ain't logging

Alan, as you can see the BEC did not affect the ESC temp much, but FF or hovering does.

I am very interested in anyone's comments as to why the power, amps and mAh on these logs vary so dramatically, and people's thoughts as to what the correct numbers should be ?

Cheers
Colin

No-one got any thoughts as to why these logs are so different (logs with BEC compared to logs with 2s A123 battery) ?

Cheers
Colin