Hi,

Just returned from the Nats and have come across an interesting anomaly that has Wayne and I scratching our heads. We did some test flights on our new electric ships there and actually had Wayne's grandson Sam fly his electric ship in Sr. Stunt. The timer and electric components performed flawlessly throughout the morning of Sam's flights with everything working just as expected. Sam was lucky enough to win Sr. Stunt, so we prepared his ship for a couple of Walker Cup flights that afternoon.

The ship sat out on the very hot tarmac all day that day. We put a fresh battery in for his first Walker Cup flight and again, everything worked flawlessly from beginning to end. After the first flight was over, Wayne and Sam swapped out the battery for a fresh one since Sam would fly again in just a couple more flights. The plane again sat out on the tarmac, this time with battery loaded, for about 20 minutes before Sam's next flight. On Sam's second flight, the motor unexpectedly shut down right after the vertical eights. It was not the timer shutting it down, we did not get the distinctive three blips of power down, it seemed to be the Schulze esc shutting it down.

Didn't get to fly again after that, but talked to some real knowledgeable electric guys here in Tampa when we went to fly at our weekly indoor R/C session. The most common theory was that we allowed the Thunderpower Pro-Lite V2 3900 mah battery to get too warm before the second flight. Learned all about the "squishes" and "puffs" that can occur because of the different chemistry these batteries use and were advised to always keep these batteries and the plane in the shade until it is time to go. We did get some "squish" in these batteries (a swelling of the plastic wrap around the battery from released gases). If you squeeze on the plastic wrap with two fingers, the wrap will squish down a bit before you feel the cells. "Puffs" are when the cells actually deform and we noticed none of these.

The general consensus was the batteries should be OK, they still charge and hold the proper charge. The chemistry in these batteries is apparently different than previous batteries and they react differently to changes in temperature. Heat them up a bit and the electrons flow like crazy, they are rated at 40C. Apparently car racers do this up to a point to get off to fast starts when using these batteries and the theory was the battery temperature was too high at the start of Sam's second flight and that is what caused the premature shutdown. Heat them up too much, and you get a squish or puff.

Finally got a brand new 3300 mah V2 battery in Friday, so went to Wayne's house this morning to do some testing. Put in the brand new fully charged 3300 battery and started a six minute test run. Purchased a fancy laser temperature gauge to measure the exact temperature of each of the components. The battery and other component temperatures were at 84 degrees at the start of the test. Running an APC 13X4.5 pusher prop. Everything started out normal, put in the arming switch, turned on the timer and the cycle began. Motor slowly spooled up to 100% power and then backed off to the 50% power setting we had programmed. After just one minute of running, the motor abruptly and prematurely shut down again. We were running this test in a static position, but measured the temperatures immediately after the test. The Plettenberg Orbit 25/12 motor was about 104 degrees, battery was about 107 degrees and Schulze speed control was about 125 degrees. In reading the literature, it does not seem we exceeded any of the maximum operating temperatures, you could touch any of them with your thumb for at least six seconds. The new battery did not develop any squish.

We ran another test by connecting our Extrema charger in wattmeter mode. In just connects between the battery and speed control via the Deans pins. If I read correctly, the Z-Tron Z.4 timer starts it routine by going to low throttle for five seconds and then spooling up to maximum throttle for another 5 seconds to find the ends of the speed range and to calibrate itself. It then ramps down to your programmed starting speed, in our case, 50%.  

Observing the wattmeter on this 40 second run through, we noticed when the timer runs the motor to maximum speed, the speed control was actually drawing 67 amps. The Schulze 18.46K F2B speed control is rated at 46/60 amps with 46 amps being the nominal load for sustained running and the 60 amps being the maximum load. We obviously are exceeding the 60 amp maximum and this is the only parameter we can find that is not within specifications. Once the motor ramped down to the 50% setting, we were only drawing 40 amps. The Schulze instructions tell you the speed controller will shut things down if too much current is drawn, but it was strange this shutdown did not occur as the motor was winding up to maximum speed in the very beginning. It did not shut down at all during the 40 second timed run-through, but it shut down every time we tried after about a minute on a six minute run-through even though it had already reached the lower power setting and was drawing only 40 amps. I have heard Schulze typically "under-rates" their speed controller specifications while others sometimes overrate theirs.

We are not sure if we might have damaged the speed controllers, but they seem to work every time, just getting the premature shutdown after about a minute of running on the ground or about four minutes in the air on the last flight.

We are really chasing the electrons tail on this one, not sure if anyone is familiar enough with these various components to send us in the right direction. Will continue to research and have already contacted Schulze for some help. The Schulze speed control and Plettenberg motor apparently work very well together based on some tests Will Hubin did on some of Paul Walkers stuff at the Nats. Might need a bigger speed control or perhaps try a different timer that does not ramp the motor up to maximum power, not sure at this point.

Any ideas or suggestions would be appreciated.

Jim Smith
(Smith Brothers Stunt)
AMA 41899

Lol . . . I won't ask. We had 9 freshly charged batteries and a meter to measure them with before installing in plane. Same thing happened with 3 different batteries.

After perusing the Schulze web site this afternoon, I now suspect our speed controller is too small but I certainly could be wrong. That particular speed control has now been discontinued and replaced by the larger 18.61K F2B speed control. It has nominal amperage for normal flight at 60 amps and max at 81 amps. Ugh,  a little more weight. Figure that must be it, but glad I learned about battery "squishes" and "puffs" anyway since I now have some.

Might be able to just use a different timer which doesn't ramp up to maximum power during the start sequence, not too sure about that, will just wait to hear from Schulze.

We all had a great time at the Nats as usual and Sam sure did a good job flying up to his ability. He was very smooth and did a great job considering the amount of practice he gets - even had a great save during the Walker Cup when his motor quit abruptly - had us all clapping on that one.

I'll post again when I hear back from Schulze or Etienne at Icare. Need to find out which controller I need for the 20/16 Plettenberg I just ordered as well.

Jim S.

Jim,

I can only think of two things that can cause an abrupt shutdown as you are describing.  One is a thermal shutdown and the other is a low voltage shutdown.  By reading your description it doesn't sound like heat is the problem.  I did some research on the 3300 Prolite V2 battery and it is rated for 66 amps continuous.  The battery voltage may be dropping below the minimum value that the esc allows and shutting the system down.  I must say that 67 amps seems quite high, but I have no experience with the the Schulze controller or Plettenberg motor.  Also, I wouldn't recommend running the power system in a static condition for very long at all.  The airflow is minimal and the static loads are greater than the in flight loads.  I would connect your wattmeter and run the system for 10 seconds or so and watch the voltage closely.  I didn't notice how many cells your are running, but you should never see less than 3 volts per cell or 12 volts for 4s and 15 volts for 5s.  Some esc's allow the user to configure the low voltage shutdown limit.  If the low voltage shutdown is set too high then it would certainly cause the situation you are describing. 

It was nice meeting you and your brother at the nats.

Good luck,
Jason

Please keep us up to date on the investigation!
take care, Darrell

Dean

How many cells in your battery?

I have experienced motor shutdowns in my RC planes due to excessive current flow in the ESC.  I agree that the size of your ESC along with high temperature is probably the root cause of your troubles.

Roger Anderson

If my math is right, and thats a big if, you only have 2600 usable mah in a 3300 pack. You would have to draw only 66% of your 40 amp static load for a 6 min flight. Is the in air load that much less?

   Rob

On those TP 3300 18.5v batteries(had 2 of them with3 flights on each) I've used them with a Rimfire 32-800kv and I've put back 2260mah on avg. And my motor output is reduced from 100% to a avg of 75-80% vs a 4 cell of the same capacity. This is why Paul is using TP 2600s in his latest plane cause the Orbit 20-16 has a kv rating of 720.