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Low C-rate with 1st flights after winter??

Old 03-27-2010, 12:54 PM
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wagen017
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Default Low C-rate with 1st flights after winter??

today went flying for the first time this year and during the second flight in a vertical line the engine sounded like a nitro engine running too lean. It just went down in RPM every now and then (this is full throttle, going up). Landed and put in another pack but again same problem. Landed quickly then!

All measurements you can get from the controller were normal (amps, temp, rev. etc.). No error messages as well. The engine seems mechanicaly fine. I also checked if any of the setups had changed (timing etc.) but all that was fine as well.

Any ideas? I think it is the controller but have no spare so I can't just exchange it to test. This controller and motor is one year old with 150 flights on it.

I fly a Jeti99+ Pletty Evo 30-10

Thanks for any thoughts.

Volkert


PS: I changed the Subject of the thread since it seems more likely I have a battery problem then ESC/Engine issue
Old 03-27-2010, 01:10 PM
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can773
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Default RE: Low C-rate with 1st flights after winter??

Do you have any low voltage cutoff (like a soft cut) set? Sounds like maybe the packs could be weak and a LVC pulling back some power to protect them. Sometimes packs are pretty weak going into second/third season for the first few cycles, especially if its cold out.

Thats all I can really think of.
Old 03-27-2010, 01:23 PM
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wagen017
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Default RE: Low C-rate with 1st flights after winter??

thought the same thing so I checked the setting (28.something volts) and the controller measured 36 volts as lowest voltage. However, I don't know if that is a measurement you can depend on. Does anybody have experience/opinions on this?

I was thinking in the same direction as you did; checked also the internal resistance but that seemed fine as well, in line with last year.

However I could go out and do a couple of flights at mid throttle to get the packs going again.

volkert
Old 03-27-2010, 03:47 PM
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burtona
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Default RE: Low C-rate with 1st flights after winter??

I had the same thing happen with my first flight this year. New True RC 5000 pack and FliteMax 5000 packs with Pletty 30-10 and 85HV CC ESC. I had to dial back the throtle ATV to 85% and the condition stopped. I could not tell the difference in the way the plane flew. I only flew the plane maybe 5-6 flights in December with borrowed TP Pro Lite 5300 packs and had not flown it since untill last week. I too would like to know what is causing this.
Old 03-27-2010, 04:02 PM
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wagen017
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Default RE: Low C-rate with 1st flights after winter??

Anybody else with similar experience? My last flights before today were in November. I stored the packs in my garage (7-10 deg. C) at 38,5 VDC (storage function of charger). Any comment on the voltage measurement of the Jeti? The read-out for lowest voltage read 36,5VDC.

Volkert
Old 03-27-2010, 09:16 PM
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Default RE: Low C-rate with 1st flights after winter??

you might check your connections to the ESC for both battery and motor. A loose connection making intermittent contact will give very strange results. If you have a loose connection to the motor, it will sometimes 'stutter'. Don't ask me how I know this....
Woodie
Old 03-28-2010, 09:16 AM
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Walt Thyng
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Default RE: Low C-rate with 1st flights after winter??

Since both packs gave you a problem any connection problem has to be from the ESC to the motor.
Since I am not familiar with weather in the Netherlands, I don't know for sure, but it sure sounds like cold batteries. When I do winter flying (25 degrees F) I keep my packs in the inside pocket of my coat.

I am not clear whether you took the low voltage reading with the motor running or how you knew the lowest voltage at the ESC was 36. If you haven't put a whatt meter of some type in the line and run the motor up to full speed, you won't really know what's going on. My latest meter is small enough to install in my palne while I fly it. When I get down it shows me average voltage, low voltage, highest amp draw and a bunch of other stuff.
Just some thoughts.
Walt
Old 03-28-2010, 09:33 AM
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wagen017
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Default RE: Low C-rate with 1st flights after winter??

All connections are good, I rechecked this morning.

The temperature was 11 deg. C.

The Jeti-99 has the option to:
1. During flight the controller is recording the following values:

Maximum and minimum temperature including the occurence moment time of the extreme value.

Maximum and minimum current including the occurence moment time of the extreme value.

Maximum and minimum voltage including the occurence moment time of the extreme value.

Maximum motor speed including the occurrence moment time of the extreme value.

Motor run time

Flight time

Error symptoms (temperature, voltage, commutation, current), if occurred


There were no strange measurements after flight. However I wonder how well it measures the lowest voltage value. Also, is there any possibility that the voltage is still OK but that the amps are lacking? (low C-rate then?).

It measured the lowest voltage (36VDC) 55 seconds after take off. You would expect this to happen more towards the end of the flight.

Volkert
Old 03-28-2010, 10:07 AM
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Chris Moon
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Default RE: Low C-rate with 1st flights after winter??

Volkert,

I would not go by the logged data unless you know the sample rate and also the controller's internal threshold to get a LVC (low voltage cut off) warning. It could happen between samples and never show up in the data. If you have a "soft" cutoff then it should pulse when it sees a momentary LVC unless the condition is sustained long enough to completely cut off.

Possibilities (no particular order):
connections - possibly had corrosion issues over the winter
batteries - low power due to long storage - possibly will improve with more break in time
batteries - low power due to cold
temp- possible over temp of controller (doubtful)
motor - damaged? (doubtful)
controller - damaged component?
controller - firmware damaged and reload necessary (I have seen this before)

If what you are getting is a loud noise and not a momentary pulsing, then that a different issue altogether.
Old 03-28-2010, 10:08 AM
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Walt Thyng
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Default RE: Low C-rate with 1st flights after winter??

I didn't realize that the J99 recorded data. Frankly, at this point I'm stumped. Old batteries could be a possibility, but it should show up in the data. maybe you could try a differetn tester.
WT
Old 03-28-2010, 10:23 AM
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Default RE: Low C-rate with 1st flights after winter??



It measured the lowest voltage (36VDC) 55 seconds after take off. You would expect this to happen more towards the end of the flight.

Volkert
Hi Volkert

That seems very suspect I think. Firstly, you are right that the lowest point should occur during the last few maneuvers of a normal pattern sequence, so maybe 5-6 minutes into the flight. Secondly, 36V is very high for any battery to hold through an entire flight. My experience is that even the best batteries will drop closer to 35V, and only when reasonably new. With a years flying on them 34V is a more normal range for the packs to be dropping to.

Another "by feel" check you can do, is fly a flight, then post flight run the motor to full throttle on the ground. It should be obvious to your ear if the motor is making any power which is a simple way to get a feel if your batteries are holding decent voltage.

Volts and amps are tied to one another, if the voltage is sagging a lot your amps will sag as well because the motor will turn less RPM, so will require less total power.

I would try to get another device to measure you pack volts/amps to see whats going on.
Old 03-28-2010, 03:52 PM
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Default RE: Low C-rate with 1st flights after winter??

Try warming your packs up to 30-40C before use.

A rubber hot water bottle in an eski or chilly bin does this nicely.

Cheers
Jason.
Old 03-29-2010, 04:02 AM
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Malcolm H
 
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Default RE: Low C-rate with 1st flights after winter??

I'm going to jump in here as I have experienced a similar problem. (Chad check your PMs).

Last year when changing from Thunderpower V1 Prolites to V2 5300 Prolites I experienced problems with two Schulze 32-80KA/Extra 30-10 setups at full throttle in uplines. The first one gave symptons you described with squealing and on examination there was a partially de-soldered 3 mm plug on the board of the controller. The second one failed big time and all that was left of the controller was the heat sink and battery wires. The motor ended up with a solder bath from the debris. The motors went back to Plett who cleaned them and test ran them and declared them undamaged. Schulze reckoned the problem was caused by voltage drop across poor quality 4mm bunch connectors upsetting the microprocessor in the controllers ability to commutate the motor properly. Although I had purchased the highest quality ones I could get in the UK, on their advice I changed all my 4mm connectors to Schultze ones and at the end of last season I had approx 20 trouble free flights.

At the start of this season I have had a number of inflight squeals which always occur on the first upline in P11 and if one throttles back a little they go away. After this there are no more problems. As it has been very cold here I have been prewarming the batteries on the car dash with the heater on until they are nice and warm to the touch. What I have discovered is that the squealing only occurs with batteries warmed significantly before flight. When they are used at room temp. around 20C there is no squealing. It would appear that the higher initial voltage under load for a warmed pack is causing the problem and as the pack discharges slightly the problem goes way. As my last season flights were made in significantly higher air temps and little or no prewarming was done there wasn't a problem.

Comments welcome and opinion on whether changing connectors to say the Plett 6mm ones would help this issue?

Malcolm
Old 03-29-2010, 04:22 AM
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Default RE: Low C-rate with 1st flights after winter??



With preheated packs at 40 deg C the Voltage drop is much lover than with packs at room temperature. At 11 deg C the Voltage drop under load can be dramatic (down to 3,3V/cell)



In the new Hacker catalog on the page 42 is given the graph for the heated and not heated cells. From there everything should be clear.



@ Malcom H If your combo is making "squeals" it means that it is on the limit of the motor load and you should prop down. Latest generation of batteries is giving much higher Voltage under load which directly reflects into higher Amps and revs (~500 for a 20" prop) further increasing the load on the motor.



Velco







Old 03-29-2010, 10:36 AM
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wagen017
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Default RE: Low C-rate with 1st flights after winter??

I just had reduced power in the uplines but no squealing. I will check my connectors for any "corrosion" or what ever.

Volkert
Old 03-29-2010, 10:39 AM
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Default RE: Low C-rate with 1st flights after winter??

Volkert,

I really would bet the batteries are just weak after "sleeping" over the winter and will come back with more use.
Old 03-29-2010, 12:11 PM
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wagen017
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Default RE: Low C-rate with 1st flights after winter??

I think so too. I will check the connectors between motor and ESC and between ESC and batteries just to be sure but I planned to just go and fly each battery 2 times on a easy program and then see what happens.

Volkert
Old 04-05-2010, 11:57 AM
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wagen017
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Default RE: Low C-rate with 1st flights after winter??

just spend a boring afternoon flying but it seems to have recovered my packs. No more power outage on vertical uplines!

Volkert

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