Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

Help, I am confused over a brown out issue??? Help

I have been flying my Aurora 9 with 6 channel Optima 6's in my electric planes and foamy's with 2 & 3 cell Lipo's, and been perfectly fine, but get this???

I finally broke out my Nitro models Bobcat with a 65 nitro and charged my receiver packs last eve, but then today on the ground, when I moved all the servo's before take off, I had a brown out several times, so I refused to fly it????
This is scary...wow, bad scenario has me wondering now, and I have the following questions in order to figure this out?

* My bobcat has my 9 channel Optima 9 in it.
* my bobcat has TWO 4-cell receiver packs connected in parrallel as I flew it last year with my JR 7207 system...worked perfect.
* I used a 'Y' harness to come off the power switch from the 2 Nicads to power the standard Rx port, then the other 'Y' connector to the SPC power to insure that I did NOT have borwn-outs...

> OK, is my sense that 4 cell NiCd is NOTsuitable for the Optima receivers (and the Aurora 9) ???? This seems crazy, did hitec pump out optima's, but yet they do NOT work on the lower voltages of the 4-cell nicad receiver packs that we all have in our nitro fleets????

> Do I maybe need to use a small 2-cell Lipo battery to connect directly into the SPC port to keep the power and voltage high enough so that the silly Optima receivers do not have brown outs in my gas & Nitro fleet????

or should I upgrade my whole fleet to 5-cell nicds instead of 4-cell nicds for the higher voltage (I hope not)?

> if Lipo voltage is a must, which is diappointing, what chart is out there to power the 6 or 7 or 9 channel optima receivers?

> if 4 cell nicds are ok, any brand better than others or what MAH power levels, the former days have been the old stand by 500 or 600 or 700 MAh packs?

HELP!!!!
Thank you in advance for the help!!

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

I just bought an A9 and I am interested in the answer you will get as well. All my planes use 4.8v Nimh....now I'm worried.

Best regards,

Chris

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

I am using 1500mh NIMH 4 cell battery sucessfully in my sailplane with 6 servos. Flys about 30 min at a time.
No brown outs...

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

I think technically the A9 can brown out at 3.5 volts. Most guy don't feel real comfortable using 4 cell packs for peace of mind. If your pack doesn't spike below 4 volts your probably ok.
When you setup your planes........try to make sure you don't have servos that are binding or over traveling causing high current draws.
If your using 3 or 4 or more digital servos I would not recommend using a 4 cell pack.
I use a 3 cell lipo to run my servos and receiver. It is on a regulator and gives a constant 5.1 volt.

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

Gizmo

The problem is not the Rx'r . You said you used these packs last year with your JR radio. When was the last time you cycled these packs to check their condition ? The real issue is the load being put on the batt.. If the servo's are drawing enough load, and the batt. packs are getting old and not performing up to snuff, then you could have a problem. I stopped using 4 cell packs along time ago for the fact that 5 cell packs give a greater safety margin. But it's all about the load. If there is binding in a linkage you have increased load on the servo & batt. You prob. should not fly a 4 cell pack down much lower than 4.8 volts for safety anyway. So There should be sufficient margin for the Rx'r to operate at less than 4 volts. In the good old days our Rx'r cut off voltage was usually higher than what it is on the Optima series and we used 4.8 volts as the reading to stop flying and go home & charge with our old 4 cell ni-cad & nickel metal packs. How did we do it then ?:)

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

Resurrecting this old thread, in hopes it'll shed light to others.


I've used two Optima9's in different planes before w/o issue. But recently am setting up a new 55cc plane using newly bought Optima 9 Rx and experienced major brownout.

I'm using 5cell sub-c 2000mah pack and so far installed 7qty PowerHD HD-1501MG metal gear servos (4 for ail, 2 for elev, and 1 rudder). I know these are cheap servos and I deserve to have glitches...okay now with that aside...

I read [link]http://www.rcgroups.com/forums/showpost.php?p=15208913&postcount=4[/link]that Optima9's min cutoff V = 3.5v. So went went to measure.

Experiment #1:
5-cell NIMH subc 2000mah via deans->wattmeter via deans to jst -> switch via jst ->Rx ch9/batt
Jumper on SPC
Measurement: Moving sticks randomly to get all servos moving unrealistically, wattmeter measured 38.5 w peak, 6.53A peak, 5.78 V min
Symptoms: Every 2-3 seconds all servo will pause for 1/2 sec, then come back on. Rx has been browned out. Worst case, sometimes when Rx has "booted" up, left aileron servo pair will "twitch" to extreme servo position before returning to stick position.

Experiment #2:
5-cell subc NIMH 2000mah via deans->wattmeter via deans to jst -> switch via jst ->Rx ch9/batt
4-cell subc NIMH 1700mah on SPC
Measurement: Moving sticks randomly to get all servos moving unrealistically, wattmeter measured 37.6 w peak, 6.44 peak, 5.65 V min
Symptoms: No brown out realized

Experiment #3:
5-cell subc NIMH 2000mah via deans to jst -> switch via jst ->Rx ch9/batt
Jumper on one end of Y cable & wattmeter-source-end to other end of Y cable ->SPC
Measurement: Moving sticks randomly to get all servos moving unrealistically, wattmeter measured 4.03 V min
Symptoms: Same as Experiment #1


Here's what I gather:
- Experiment 1 & 2 proves brownout was at Rx, not my servos.
- Experiment 3 proves that there has been a significant voltage drop at 4.03V at SPC jumper location (possibly the Rx's power trace/rail) causing Rx brownout. It is interesting that Vmin in Experiment 1 was at 5.78V, this is what is provided to the Rx at Ch9/Batt slot. I wonder if the pcb power tap trace from Rx power rail on CH1 thru 9 feeding to SPC jumper was too thin causing a voltage drop? May have to google for pics or do it myself.
- Optima 9's minimal voltage is around 4.0v and not 3.5v? So, there must be an internal-BEC on the SPC backend, it maybe that they spec 3.5v to Rx's CPU ( internal-BEC's output voltage), however through normal losses of a BEC, the input to the BEC must be higher than 3.5v...who knows...


Ultimately, I still like Hitec. My solution will be to:
1) power the Rx through SPC with a 2C or 3C lipo
2) use a 5c NIMH 2000mah pack for the servos
3) beef up the switch wiring. The std servo sized wiring it came with got warm to the touch.

Happy flying!

-Dan


BTW: I don't have a fancy fluke DVM to measure the actual accuracy of the Turnigy Wattmeter, but Turnigy claims +/- 0.01v.

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

Use a LIFE pack and get rid of the High resistance NIMH packs. Simple!

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

LiFe pack on the Rx's Ch9/Batt post? I'll assume going thru a external BEC first, else you'll possibly blow your servos with 7.2v?

So a fellow RC guy recommended that I use a lipo -> BEC set to 6v. I suppose I could try it and see. I'm skeptical of this working since Experiment #1 has shown the NIMH pack didn't sag below 5.78v. The drop was at the SPC in my findings...

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

The Hyperion LiFe two cell pack comes in at 6.6 volts has been working fine on the receiver packs for both my A9s. Some 20 odd planes with no regulator. Its all I use now including my ignition modules.

Dennis

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

I always use 5 cell batteries.  I prefer NiCds but do use NiMh batteries.  My philosophy is why take a risk.  So I use 5 cell 2000 milliampere hours and up batteries.  The NiCd can deliver faster than the NiMh and dies gracefully,  The NiMh is lighter, smaller in size for the same capacity in milliampere hours.

Brown outs occur due to demand on the battery.  If you have five or more servos they will suck up more power.  Planes with sever servos and a receiver can demand as much as a 1,000 milliamperes of power when all are moving around.  The receiver probably demands 20 to 30 milliampere hours of power by itself.  So think in terms of power budget.  It is true we rarely use all seven servos at once but they are there and can do it.  Remember servos have a motor in them, and when you command it to move, it draws a "start up current load" to get started.  These can be instantaneous peaks.  A hung servo can draw a lot of power too.  So capacity is important.

When a battery's capacity is taxed to heavily, the voltage will drop some times very very rapidly.  That is when brown out occurs. The 4.8V, 600 milliampere battery is woefully under sized and capacity.  It is the minimum for a four channel set up.  Most of us have five or more servos.  More powerful servos, more torque, digital, demand more power. 

So do not skimp on batteries or their capacity.  Think of it like a fuel tank.  A little one only allows you to fly a short time.  A big one lets you fly a long time.</p>

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

I assume you setup exp 3 like the picture but without BEC as the battery was a 5 cell NiMH. The only way I can see that exp 1 and exp 3 produce similar bad results and exp 2 produce good results is with the 2000 mAh NiMH pack voltage dropping to below the Rx brownout voltage. Exp 3 should have bypassed the internal suspect traces in the Rx between the servo power and Rx power lines since you removed the jumper. You definitely need to use a battery that can handle the current requirements without dropping voltage too far. The LiFe is a good suggestion, or a Lipo with regulator. You should not have to use 2 batteries. Since your 7 analog servos are drawing over 6 A of current, I wouldn't be surprised if one or more of them is rubbing, jamming, or stalling to some extent. Try debugging each one by using your wattmeter to catch the suspect. I'm curious to see what you discover.

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

The HK LIFE packs 1100mah are 6.6volts also and I have been using them for over a year. About 15 people in our club have been changing over. No problems. I am now experimenting with 1800's for combined rx and onboard glow(glow device draws about an amp at 6.6v), one pack. So far. So good.<div>Highly recommend life 2s.</div>

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

Hi wayupnorth,

The purpose of Exp3 was to measure voltage at the SPC (jumpered). To do this with using the wattmeter, I used a Y cable at the SPC. In one end of the Y cable: Jumper. On the other end of the Y cable: wattmeter @ source connector, which allows the wattmeter to measure the voltage and keep track of the min voltage.

Exp 3 is almost like the picture you've attached, except I didn't tap directly from the battery to the SPC.

I will spend some time to make a cable to measure how much power each servo is consuming. May take a few days to repost.

RE: Aurora 9 with Optima Rx Brown out Q&A - Rx 4 or 5cell??
 

Thanks for the suggestion 4*60. I may get some LiFe packs to experiment. I'd like to get what I have to work first before dipping into LiFe. My charger doesn't support LiFe, so will have to get that also... :-(