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Oct 09, 2002, 11:47 AM
Thread OP

thought my Qualcomms were dead


I may be stating the obvious but...Qualcomms and an M-100 do not play nice with a GWS 2 amp esc. Unfortunately I never bothered to check the setup on a meter.

While flying my IFO-T the engine was shutting off after +/- 4 minutes of flight. I initially thought the voltage dropped in the battery and the bec was doing its job.....but after trying to charge the battery again i discovered the battery was nearly full??!!

The next flight was strange....flying at 2/3 power was no problem, but full throttle for more than a minute would shut down the motor. If i had enough altitude i could get the engine to kick back on before i reached the ground.

Guess i am caught riding a roller coaster until the 5 amp esc arrives....

Will overloading the two amp shorten its life?? Or does it have a safety cutoff??
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Oct 09, 2002, 12:59 PM
Our Daddy and Heli Junkie
Fred Bronk's Avatar
If the ESC is going into thermal shutdown (like it sounds), it should come back on after it cools down (as you say).

BEC is the battery eleimator circut and does not shut off ever.

If the LVC (low voltage cutoff) is cutting in a 5 amp ESC will not solve the problem. If the cells v drops bellow the LVC # that has nothing to do with power the motor draws.
Oct 09, 2002, 01:54 PM
DNA
DNA
registered user
DNA's Avatar
Lem,

The QCs have an internal PTC device that will shut down the
cells when the current being drawn from them is too high.
That means you'll lose power temporarily while flying if you are
drawing more than ~3 amps from them. The PTC device will
recover and allow the voltage to rise and the current to flow
again, so you can restart the motor. The M100 is drawing more
than 3 amps at full throttle so the PTC shuts the cells down to
prevent damage to them. A new esc won't make any difference.
Oct 09, 2002, 02:02 PM
Is just the motor cutting out or are you losing power to the servos too?

When the PTC in the cells activates you lose all power.

Possibly a smaller prop would draw less current and eliminate the problem. Other folks have learned to tell when the cells are sagging and back off on the throttle enough to let them recover without the thermal cutoff.

I can never tell until everything shuts off, and then it's too late.

BC
Oct 09, 2002, 08:27 PM
Thread OP
When the motor quits i still have servo control, so i am guessing itís not the batteries.

Is the internal PTC within the cells??? i have removed the ic board that was in the qualcomm pack. now i only use it when charging.

I am using a GWS 1047 prop, which i know is a bit big. The setup has lots of thrust and the batteries are just slightly warm after use. Because of this i have been procrastinating changing anything....

I guess tomorrow i will try a smaller prop...
Oct 09, 2002, 08:40 PM
Crash Master
Gene Bond's Avatar
The esc is shutting down on thermal, it sounds like to me. The PTC inside the cells gives more of a voltage sag, which could trip the LVC, but I've never seen total loss of radio, except from the protection circuit. When they cut out, there's no power to anything until reset.

I have killed 2 packs this week, probably due to abuse, but at no time have I seen anything other than premature LVC cut-out, following a power sag.
Oct 09, 2002, 08:47 PM
Quote:
Originally posted by lemmeatthem
When the motor quits i still have servo control, so i am guessing itís not the batteries.

Is the internal PTC within the cells??? i have removed the ic board that was in the qualcomm pack. now i only use it when charging.

I am using a GWS 1047 prop, which i know is a bit big. The setup has lots of thrust and the batteries are just slightly warm after use. Because of this i have been procrastinating changing anything....

I guess tomorrow i will try a smaller prop...

the PTC is inside the cells. removing the charging circut won't remove the PTC.

It really sounds like you are overtaxing your QCs. I've done the same thing, drawing up to 4A at times, and get exactly the same results.

what happens, is that the qualcomms get overworked, then PTC drops the voltage, then the LVC kicks in. This allows the cells to recover voltage immediately, so you have control still.

just cycle the throttle to off, then to 50% power, and come in for landing.

you need to keep the amp draw UNDER 3A, as you are only shortening the life of your QCs. The ones I most abused only put out about 2A now, and have been retired to IPS setups only.
Oct 09, 2002, 08:54 PM
Quote:
Originally posted by Basketcase
Is just the motor cutting out or are you losing power to the servos too?

When the PTC in the cells activates you lose all power.

BC

I don't agree...

the PTC slowly chokes back the voltage if your amp draw is too high. I've abused several QC packs, and never had a complete loss of power... ever.

Are you thinking of the protection circut? If you overload that, it will indeed cut all power, and you will fall from the sky.

As I just posted, when the PTC thermistor kicks in, and the voltage sags under what the LVC is set to, the motor is shut off. This causes the cells to be able to recover, and voltage rises again.

I repeat: I've never had a total loss of power to the flight electronics when flying with qualcomms.
Oct 09, 2002, 09:36 PM
Registered User
Notoatmeal, I agree with you. I've had several cases where my motor shut down in mid-flight. Simply cycling the throttle off and then back up to about 50 percent kept me in the air. After about the third time this happened, my throttle reflex became automatic.
Oct 09, 2002, 11:05 PM
Strange Plane Central
frankenfoamy's Avatar
I had the same thing happened when I used three qualcomms with the 2 amp GWS ESC two servos and a dual IPS

Guess they really mean 4-8 cells when they print it on the ESC.

http://rcguy.tripod.com/
Oct 10, 2002, 05:44 AM
Rehab is for quitters
LuckyArmpit's Avatar
I run a M-100 motor and GWS prop (modded 7x6 to 7x8) on my Varmint with 830 Qualcomms and it has never shut down. Of course I have the protection circuit only on the charger. Also running a GWS 5 amp esc on it.


Dave...
Oct 28, 2002, 03:45 PM

HELP!!


Guys, I need some help. I made 3 Qualcomm (QC) battery packs last week. FIRST PACK: Flew my PICO J3 cub at near wide-open throttle and the pack lasted only 8-10 minutes. Plane seemed to experienced a decrease in throttle prior to shutdown. End of that pack, which had been fully charged. SECOND PACK: same thing as First Flight. THIRD PACK: nothing worked, inluding the motor. I disconnected the ECS and hooked the battery to the motor for a second. The motor worked. Rehooked the ESC and tried again, NOTHING. Complete loss of power. The servos did nothing but rattle and twitch severely. The 2 amp ESC was a little warm to the touch, but not hot.....What's causing this? Should I get a larger, 5-20 amp ESC? Or should I put the battery leads on the B+/B- posts?

Thanks, Franz
Oct 28, 2002, 04:20 PM

HELP!!


Guys, I need some help. I made 3 Qualcomm (QC) battery packs last week. FIRST PACK: Flew my PICO J3 cub at near wide-open throttle and the pack lasted only 8-10 minutes. Plane seemed to experienced a decrease in throttle prior to shutdown. End of that pack, which had been fully charged. SECOND PACK: same thing as First Flight. THIRD PACK: nothing worked, inluding the motor. I disconnected the ECS and hooked the battery to the motor for a second. The motor worked. Rehooked the ESC and tried again, NOTHING. Complete loss of power. The servos did nothing but rattle and twitch severely. The 2 amp ESC was a little warm to the touch, but not hot.....What's causing this? Should I get a larger, 5-20 amp ESC? Or should I put the battery leads on the B+/B- posts?

Thanks, Franz
Oct 28, 2002, 04:58 PM
Live to ride... and fly!
Tres Wright's Avatar
Sounds like you may have a bad ESC. What ESC are you running? 2 amp should be fine for a Stik on QCs.

Do you have a way to check voltage on your batteries? I'd be interested in hearing what your voltage reading was before and after the 2 successful flights. You should get 30+ minutes easily on that setup. You should be charging to 8.2 to 8.4 volts and discharging to around 7.4 volts. That should give you about 30 minutes of flight. But, if your ESC went bad, it may have been giving up a lot of that energy as heat until it finally fried.
Oct 28, 2002, 04:59 PM

Additional Comment to Previous Post


Sorry about the double post. Adding to my previous post, I want to tell you guys that I have soldered my battery connections to the charging posts (+/-) and not the battery posts (B+/B-).

Thanks, Franz


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