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HomeAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Results of running 5 cell RX pack...
07-21-2002 04:07 AM  16 years agoPost 1
ncostes

rrVeteran

Va, US

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Ran my first 5 cell nicad rx pack today. Here is some info in case others are thinking about this...

The pack is a 1400mAh pack from Radical RC http://members.aol.com/davthacker/radicalrcindex.htm

My heli is a Hawk IV, with an 8 channel hitec/rcd rx, a century pg2000V2 gyro (dual rate/remote gain - NOT HH), and 5 hitec/rcd 425BB servos.

1. Run time: I flew 8 tanks at about 25 mins per tank.

2. When I was done voltage was about 6.2V (when I started it was about 6.8V). I test voltage with a rig I made that draws 300mA, measure the voltage accross the resistor that has this current running through it.

3. The pack well outlasted my TX pack, had to recharge that at the field.

4. The servos are quicker as expected.

5. No glitches or problems.

Overall, the 5 cell pack gets a "2 thumbs up".

Nick

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07-22-2002 01:52 PM  16 years agoPost 2
AMCross

rrApprentice

champaign IL

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Nick,
One thing to note -- please double check with your gyro/governor/servo manufacturers to ensure their equipment is designed to stand up to the rigors of unregulated 6V. Futaba gyros/governor are NOT intended for this environment and require a regulator to keep the max voltage below 6.0.

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07-23-2002 04:08 AM  16 years agoPost 3
ncostes

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Va, US

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AMC,

Thanks for the info. That is an interesting point. My century gyro is rated to use 4.8-7.2V - however it did crap out towards the end of the day, would not work above minimum gain resolution, and even there would only compensate for CCW yaw!

It had been through a crash 2 weekends before (none of the electronics were damaged, and the gyro was on the servo tray) and had worked fine for another gallon since then.

I'll see if Century wants to repair it under warranty or if it's my problem because of the previous crash. They basically give it away free with their kits when you catch them with their little deal going. It's kind of funny that I can buy a complete heli w/gyro for what some gyros + servo cost

The hitec rx and servos are rated to 6v - doubt the extra .8 V really causes them problems - if the rating is that close we're in trouble even with 6v regulated, but I suppose a regulator will provide more consistent response throughout the day.

So thanks for taking the time to post, now I have to go order some parts from mouser

Nick

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07-23-2002 05:33 AM  15 years agoPost 4
irq

rrKey Veteran

San Diego, CA

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You still have to be careful though, I've seen situations where a gizmo was "rated 6V" and when I called the manufacturer they said "exactly 6V is the absolute maximum voltage you can put in".. so using a non-regulated 6V battery with such a device would be Bad.

However, Ray, in his Helicopter Manual, strongly recommends using a 5-cell (6V) pack with a regulator that spits out 4.8v.. he recommends this because if one of your cells ever goes bad in a flight, you can still have enough juice left to land. In a 4-cell pack, that isn't the case. Still, I've never had a cell break in flight, but it may happen some day

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07-23-2002 07:20 AM  15 years agoPost 5
ncostes

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Va, US

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Well the consensus is I should be using a regulator...

http://www.runryder.com/showtopic.h...2&topicid=16110

So I will be putting together one based on a switching regulator.

The happy news is with a switching regulator with such a small differencen between Vin and Vout = high efficiency, I should see even LONGER run times

Thanks for your input!
Nick

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07-24-2002 04:40 AM  15 years agoPost 6
Julius

rrNovice

Tracy CA

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5 cell vs 4 cell
Nick,
Save yourself the hassles and extra weight of a 5 cell system. WIth the battery technology today, pack failures are almost non-existent. Believe it or not, a 4 cell 1400 mah pack will outlast a 5 cell 1400 pack. If you want added flight time, increase the Mah of the pack, 1800, 2000 ect. in a Nimh. You'll be much better off.

julius

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07-24-2002 02:29 PM  15 years agoPost 7
ncostes

rrVeteran

Va, US

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Julius
Thanks for the info. With a switched regulator (which operates in saturation mode - on/off (as opposed to the traditional linear regulator (e.g. 7805) which is always sinking current) I should definitely get more run time with a 5 cell pack than an equiv. 4 cell pack. I will post my run times.
Thanks
Nick

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07-25-2002 04:26 AM  15 years agoPost 8
Flighttime

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Cincinnati, Ohio

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K.I.S.S.
I was very frustrated with the run times of those small 1100 nicads. I switched to 5 cel nimh. However, all I've read said to regulate. Tried it and did'nt like the additional complexity. More points of faulire. Besides, I have never heard a complaint with unregulated 4.8v.
So to simplify and have reliability I went with 2 2700 nimh packs. Both properly maintained with a Orbit Microlader v6.0. I'm getting 10+ flights w/o even leaving the green (5.1 - 4.8v) on my onboard voltmeter.
You see, I just wanted to fuel and fly "All Day Long".
I'm flying a R60, OS91 w/ Hatori SAB-18F, TT carbon blades
2 Futaba 9253 (thro & rudd)
3 Futaba 9303
GV-1, and Gy401
That's a fair drain w/o being all digital.
I'm having a great time !!! and that's what I'm after.

Hope this helps !

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07-25-2002 01:02 PM  15 years agoPost 9
ncostes

rrVeteran

Va, US

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Thanks for all the feedback. Maybe going to 5 cells was a mistake - maybe not. The additional speed is nice to have as is the run time, for less cost than a higher than 1400mah cap. 4 cell pack would have cost.

Started another topic to find out what regs. people use, just out of curiosity. Since i haven't had a chance to order parts for mine this weekend I'll have to live with a voltage divider just to drop the voltage closer to 6V to start.

Thanks again.
Nick

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