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CanoMod . Futaba-RC . A Main Hobbies

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Main Discussion > Average Current Consumption
 
 
KCTVeteran - Location: Ontario, Canada -
Hi to All,

lately I have witnessed a rough landing that was probably caused due to lack of battery power.
To be more specific the tail went crazy while been inverted, immedeatly after some very
aggressive piro flip's.

A short mpg clip can be found on the bottom of Sluggo's Gallery.

I would like to know how much "average" current draw one will have
in a 8 minute beating of a Fury Extreme with YS90, MAH blades and fully loaded with the latest
digital Futaba gear. I would also like to know opinions on battery packs, capacity, technology
and preferences / reasons to fly a certain pack.
My guess/estimation is that during such a flight about 500mA will be drawn out of the pack.

How much capacity "redundency"/reserve do you think would be appropriate or desired to
ensure a safe and trouble free operation.

If you are a experienced hobbyist preferly with some electrical background please respond.
Actual measurements or data input is highly appreciated.

Cheers

Kay


That's not flying, that's crashing with style...

TeamBob00, WildCat, Helitron
07-28-2003 Over year old.
HOMEPAGE  
 
 
Phil Cole
Veteran
Location: Redwood City CA

I figured this out for my X-Cell 60 with 8231s and a GY-601.

It came to something around 2 A.

I did it by logging flight times on a couple of different days then measuring the remaining charge in the battery each time. I compared this to the measured capacity of the battery from a full charge. All this was done using the same charger, so the discharger function's cutoff voltage didn't matter, so long as it was consistent. I used a Litco Alpha 4 for the measurements. The pack I used was made from four 1800 mA-h A-size Sanyo Nicads. They may be KR1800AUs, but I can't be sure.
07-29-2003 Over year old.
 
 
AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

For a Raptor 50 with analog servos and a 401/9253, I use up about 180mah per 10 min. flight. That's about 1.1A average current draw during flight.

I expect that digital servos may double that figure.

Wolfgang
07-29-2003 Over year old.
HOMEPAGE  
 
 
KCT
Veteran
Location: Ontario, Canada

Thanks for the replies so far.
Does anyone has measured or any idea what the peak current will be ?

AirWolfRC

which kind of battery pack did you use ?



Thanks again

Kay


That's not flying, that's crashing with style...

TeamBob00, WildCat, Helitron
07-29-2003 Over year old.
HOMEPAGE  
 
 
Dragon2115
Key Veteran
Location: New England

My Fury Extreme with, full digitals, CSM560, and GV-1 uses 330 mAh per 10 minute flight for an average current of 2 amps. Calculation was done the same way as Phil did his. I use a 5 cell KR1700-AAU NiCd with a 5.2 volt regulator. I use the 5 cell pack and regulator so that I have reserve capacity to handle the surge currents while still maintaining the desired voltage.
07-29-2003 Over year old.
HOMEPAGE  
 
 
AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

I am using a 1700 mah pack and figured my numbers by checking the remaining capacity of the pack after 4 to 8 flights (multiple measurements) and after verifying the pack total capacity.

Wolfgang
07-29-2003 Over year old.
HOMEPAGE  
 
 
bob00
Veteran
Location: Toronto, ON

Hi Kay,

Approx. 830+mah for 8min 3 all-out flights and approx. 1100mah for 4.Fury Ex / YS90 / 9252 / GV-1 / GY601.

This puts the avg. at around 276mah used per flight. By this crude calculation the avg. current draw would be about 2 amps.

This seems to be heavily dependent on the model as my Nova and Mille used 400+ per flight. The Viggy was somewhere in between.

- Rob
07-29-2003 Over year old.
HOMEPAGE  
 
 
limey
Senior Heliman
Location: Pittsburgh,PA

I fly a Milli with all the toys for 3 flights and then charge. Anymore and I can feel the tail starting to let go. This is with Futaba's 1500mah battery. When charging it takes anywhere from 400-800mah to come back to full charge.

Steve.
07-31-2003 Over year old.
 
 
KCT
Veteran
Location: Ontario, Canada

Hi Robert,

well I looked into it a bit further and here is what I can come up with.

As you know I fly all digital JR crap except for the govonour. With my Expert NMHI pack rated at 2700 mA after two flights beating (with the help of Chris) of 8 minutes each I went home and discharged the battery pack with a constant dicharge current of 700 mA. Once fully discharged my charger displayed a remainging charge of 2070 mA. The pack has as per my charger a useful discharge capacity of 2650 mA at a discharge voltage of 4.66 V.

By approximation that would make 580 mA for two flights or 290 mA for one flight. Which seems about right compared with your figures.

Based on these figures one could theroretically fly ninetimes of 8 minutes on this pack before recharging - which I believe is not realistically.

How did you come figure the average current ?


That's not flying, that's crashing with style...

TeamBob00, WildCat, Helitron
08-01-2003 Over year old.
HOMEPAGE  
 
 
Phil Cole
Veteran
Location: Redwood City CA

Calculating the current is fairly easy.

Remember that battery capacity is measured in mA hours, not mA.

You used up 580 mA.h in 16 minutes.

580 mA.h x 60 minutes/hour = 34800 mA

34800 mA.minutes / 16 minutes = 2175 mA = 2.175 A
08-01-2003 Over year old.
 
 
KCT
Veteran
Location: Ontario, Canada

Thanks Phil, you are right mA/h it is. As for the average current, I can follow that. Does anybody know if the Internal Resistance of a battery pack is variable dependent of the remaining charge ? And if so in which relationship ? How far is temperature an issue compared NiCd with NiMh ?

Cheers

Kay


That's not flying, that's crashing with style...

TeamBob00, WildCat, Helitron
08-01-2003 Over year old.
HOMEPAGE  
 
 
BladeRunner
Elite Veteran
Location: Ontario Canada. Member of "some sort" s

Kay, check out Robert's site. I saw something interesting there about NiMH and NiCD comparisons. He was saying that the NiMHi just wasn't up to the task when "push" comes to shove........ That's not a quote...but you get the meaning. The NiCD's seem to have that extra "bit" of juice left when you really need it.......that's what I got from it anyway......correct me if I have it wrong.........
08-01-2003 Over year old.
 
 
KCT
Veteran
Location: Ontario, Canada

Yes, Barry I am aware of Robert's site. Basically what he was saing that the pack could not deliver the required current. That is precisely what I am trying to find out, Why. If we compare the average current draw of approx. 2 A with an average current draw (much higher than 2A) of an electric powered "toy" with the same battery technology, I am wondering what makes the difference. It seems the pack can deliver much higher current sustained for a periode of time.

Cheers

Kay


That's not flying, that's crashing with style...

TeamBob00, WildCat, Helitron
08-01-2003 Over year old.
HOMEPAGE  
 
 
BladeRunner
Elite Veteran
Location: Ontario Canada. Member of "some sort" s

I believe the internal resistance is less in the NiMH packs, and they release ( for lack of a better term) stored energy faster. Don't quote me on this......I've been wrong before!!! Ya, I remember once back in 68'...I think it was a Tues; I might have been wrong that time........
08-01-2003 Over year old.
 
 
Dragon2115
Key Veteran
Location: New England

"I thought I was wrong once, but it turned out I was mistaken."

For the same physical size cell internal resistance is higher for NiMh than NiCd. That's why NiCd can deliver more current while maintaining the desired voltage better than NiMh can for the same size cell. NiMh's are ideal for transmitters where the load current is fairly low and constant. They don't work out as well, in terms of maintaining full voltage, when the current exceeds 1C and is constantly changing.
08-02-2003 Over year old.
HOMEPAGE  
 
 
z11355
rrMaster
Location: 10000 is enough time wasted.

Bladerunner,

As Mr. 2115 pointed out, your info
is not correct. NiMHs have higher
internal resistance which manifests
itself as lower output voltage as current
output goes up.

go to www.sanyo.com and go under
either batteries or industrial (or was
it industrial batteries?). You can do a
search and see the characteristics of
the cells we use.
08-02-2003 Over year old.
HOMEPAGE  
 
 
BladeRunner
Elite Veteran
Location: Ontario Canada. Member of "some sort" s

Thanks Dragon & Z....I thought I might have it backwards.......I stand corrected....
08-02-2003 Over year old.
 
 
sluggo
Elite Veteran
Location: Kitchener Ont

raptorrecker What battery are you using? I am getting about the same from my heli with the same gear. Most flights end up being around 275mah to 350mah depending on how much backwards and prios is done in the flight.

Chris
08-02-2003 Over year old.
HOMEPAGE  
 
 
AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

Well here it is so far;

(This chart has been moved further down this list to save D/L time)

Note that I'm using ANALOG servos to get that 1.1A

Wolfgang
08-02-2003 Over year old.
HOMEPAGE  
 
 
donlynn
Key Veteran
Location: New Zealand

Gidday

Nice table !!!!!!!!

this bloke has talent !

Regards Don
08-03-2003 Over year old.
 
 
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