SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jul 30, 2005, 04:39 PM
PWP!
ajroahkni's Avatar
USA, HI, Makawao
Joined Oct 2002
3,910 Posts
Battery-Servo question

Is there some sort of guide or chart around that one can look at to see if/how long a battery will run some servos?

For instance: I have 2 hs85mgs, and would really like to use a 4.8v nimh 300 mah with it because of the size, but am afraid of not having enough juice in the batteries.

Your input is appreciated.
ajroahkni is offline Find More Posts by ajroahkni
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 30, 2005, 04:48 PM
Tearing the Skies a new one...
Sensiblenick's Avatar
Sweden: Ystad
Joined Oct 2004
4,013 Posts
That's a mini/micro servo right?

You should be easily ok for a reliable 4 hours of average flight... I'm unsure of a chart's existance, but a 600mah pack used to be considered fine for a plane using 4 standard servos...

Your 85's can't be big on the "we suck power" scale....
Sensiblenick is offline Find More Posts by Sensiblenick
Reply With Quote
Old Jul 30, 2005, 04:57 PM
racing fool
Elmer's Avatar
Seattle
Joined May 2005
353 Posts
You need one of these, an inflight current logger.

http://www.dimensionengineering.com/ServoSensePlus.htm
Elmer is offline Find More Posts by Elmer
Reply With Quote
Old Jul 30, 2005, 04:59 PM
Tearing the Skies a new one...
Sensiblenick's Avatar
Sweden: Ystad
Joined Oct 2004
4,013 Posts
Do I need one too? Never even knew they existed...

EDIT: just read the description.... that's a smart lil' thing innit!!
Sensiblenick is offline Find More Posts by Sensiblenick
Reply With Quote
Old Jul 30, 2005, 08:44 PM
PWP!
ajroahkni's Avatar
USA, HI, Makawao
Joined Oct 2002
3,910 Posts
Quote:
Originally Posted by Elmer
You need one of these, an inflight current logger.

http://www.dimensionengineering.com/ServoSensePlus.htm
How does this work? I make close fly-bys and count the flashing lights?
ajroahkni is offline Find More Posts by ajroahkni
Reply With Quote
Old Jul 30, 2005, 08:49 PM
Feeling FrSky
surfimp's Avatar
United States, CA, Santa Barbara
Joined Feb 2003
20,086 Posts
You can guesstimate based on the stats provided for the servo. Granted, the current drains reported there are no-load so they aren't necessarily accurate, but I guess it can help you get in the ballpark. Only other way that I can think of to know for sure is to do some load testing, but to really do that right you've got to fly the plane.

If you're feeling brave just fly till the battery dies, making sure to note when you turned it on and when you turned it off....

Steve
surfimp is offline Find More Posts by surfimp
RCG Plus Member
Old Jul 31, 2005, 12:42 AM
PWP!
ajroahkni's Avatar
USA, HI, Makawao
Joined Oct 2002
3,910 Posts
Steve,

I thought about the load thing, but can't make sense of it.

From servocity.com:
Detailed Specifications

Control System: +Pulse Width Control 1500usec Neutral
Required Pulse: 3-5 Volt Peak to Peak Square Wave
Operating Voltage: 4.8-6.0 Volts
Operating Temperature Range: -20 to +60 Degree C
Operating Speed (4.8V): 0.16sec/60 degrees at no load
Operating Speed (6.0V): 0.14sec/60 degrees at no load
Stall Torque (4.8V): 41.66 oz/in. (3kg.cm)
Stall Torque (6.0V): 48.6 oz/in. (3.5kg.cm)
Operating Angle: 40 Deg. one side pulse traveling 400usec
360 Modifiable: Yes
Direction: Clockwise/Pulse Traveling 1500 to 1900usec
Current Drain (4.8V): 8mA/idle and 240mA no load operating
Current Drain (6.0V): 8.6mA/idle and 260mA no load operating
Dead Band Width: 8usec
Motor Type: 3 Pole Ferrite
Potentiometer Drive: Direct Drive
Bearing Type: Single Ball Bearing
Gear Type: 4 Metal and 1 Nylon
Connector Wire Length: 6.29" (160mm)
Dimensions: 1.14" x 0.51"x 1.18" (29 x 13 x 30mm)
Weight: 0.80oz (22.1g)

What does it mean? Battery is 300 mah 4 cell.

Thanks,
John
ajroahkni is offline Find More Posts by ajroahkni
Reply With Quote
Old Jul 31, 2005, 01:33 AM
racing fool
Elmer's Avatar
Seattle
Joined May 2005
353 Posts
Quote:
Originally Posted by ajroahkni
How does this work? I make close fly-bys and count the flashing lights?
It goes between your battery and receiver. Fly with it for
a while, then when you land count the flashing lights.

Or turn it on in your living room and wiggle the sticks for
30 seconds then count the flashing lights.

Quote:
Originally Posted by Sensiblenick
Do I need one too? Never even knew they existed...
EDIT: just read the description.... that's a smart lil' thing innit!!
With the average current it's easy to figure out how long I can fly.

The max current can tell you if a servo is bound up. I just knew three
JR micro servos couldn't draw 1.5 amps. Sure enough an aileron was stuck.

Very slick little gadget.
Elmer is offline Find More Posts by Elmer
Reply With Quote
Old Jul 31, 2005, 03:22 AM
Something MUST FLY!
IMoonBark's Avatar
OC, there is no "The OC"
Joined Jun 2004
1,070 Posts
I have a few 270 mAh NiMh 4.8v cells that fly a Pre owned floater with 2 HS-81s (I know shoot me now for still owning some) and it will fly at least 4 hours, no troubles at all.

Your mileage may vary.
IMoonBark is offline Find More Posts by IMoonBark
Reply With Quote
Old Jul 31, 2005, 03:38 AM
PWP!
ajroahkni's Avatar
USA, HI, Makawao
Joined Oct 2002
3,910 Posts
Thanks for the info Brad. That gives me some confidence in the 300 mah.
ajroahkni is offline Find More Posts by ajroahkni
Reply With Quote
Old Jul 31, 2005, 06:21 AM
Tearing the Skies a new one...
Sensiblenick's Avatar
Sweden: Ystad
Joined Oct 2004
4,013 Posts
That little Device seems .... Excessively high-tech, but in the light of that "bound servo producig high currents It's nearly indespensable!!

I might just have to get one.... wonder how to avoid the double-cost due to import tax...
Sensiblenick is offline Find More Posts by Sensiblenick
Reply With Quote
Old Aug 01, 2005, 06:23 AM
Horned one
zero-zero's Avatar
Vigo, Spain
Joined Sep 2004
759 Posts
Or you can use one of these: http://www.skykingrcproducts.com/acc...del_alarm.html
It'll warn you about batteries getting too low to fly, plus it'll also help you locate the plane if you ever go down in a difficult area. They are very light and easy to use, considering the features you get.

That said, 300 mah seems awfully small for my tastes.
zero-zero is offline Find More Posts by zero-zero
Reply With Quote
Old Aug 01, 2005, 07:10 AM
Engine? No, thanks.
Leonardo's Avatar
Firenze (Florence, Florenz, Florencia) Italy
Joined May 2005
557 Posts
Quote:
Originally Posted by zero-zero
That said, 300 mah seems awfully small for my tastes.
...me too. I use 1600 mah and absolutely NOT NICHEL-METAL-HYDRATE. I don't want my flights end with an 'uncontrolled' dive into the slope.... If a Nimh battery charge goes low, it doesn't even give you the time to count a single flashing light...
Only NICHEL CADMIUM batteries, please!! Change them every year and toss them into their proper litter baskets (they're polluting).

Marco aka Leo
Leonardo is offline Find More Posts by Leonardo
Reply With Quote
Old Aug 01, 2005, 07:33 AM
Tearing the Skies a new one...
Sensiblenick's Avatar
Sweden: Ystad
Joined Oct 2004
4,013 Posts
Quote:
Originally Posted by Leonardo
...me too. I use 1600 mah and absolutely NOT NICHEL-METAL-HYDRATE. I don't want my flights end with an 'uncontrolled' dive into the slope.... If a Nimh battery charge goes low, it doesn't even give you the time to count a single flashing light...
Only NICHEL CADMIUM batteries, please!! Change them every year and toss them into their proper litter baskets (they're polluting).

Marco aka Leo
Nickel Metal Hydrides Do have a steep discharge curve once they come off peak, But you shouldn't be flying when your batteries are in danger of giving out anyway!!

The BIG advantage of NiMh batteries is that they are very happy to be "Topped Up" where as this damages the capacity of NiCd's

I fly with NiMh batteries, and top them up before each session. My controller however has 3000Mah NiCds in it, and that gets full discharge/recharge cycles whenever it needs it.
Sensiblenick is offline Find More Posts by Sensiblenick
Reply With Quote
Old Aug 01, 2005, 08:44 AM
Engine? No, thanks.
Leonardo's Avatar
Firenze (Florence, Florenz, Florencia) Italy
Joined May 2005
557 Posts
Quote:
Originally Posted by Sensiblenick
Nickel Metal Hydrides Do have a steep discharge curve once they come off peak, But you shouldn't be flying when your batteries are in danger of giving out anyway!!

The BIG advantage of NiMh batteries is that they are very happy to be "Topped Up" where as this damages the capacity of NiCd's

I fly with NiMh batteries, and top them up before each session. My controller however has 3000Mah NiCds in it, and that gets full discharge/recharge cycles whenever it needs it.
I well know the pros of NiMH batts such as tolerance of 'top-up' charging and no 'memory effect', but I still prefer my old NiCads. That's because I'm scared by the well known 'absent-mindedness factor' affecting most of us slopers. You know, time passes very swiftly and this could mean forgetting the batts.... ("Put your hand on a hot stove for a minute, and it seems like an hour. Sit with a pretty girl for an hour, and it seems like a minute." Einstein - Theory of Relativity )
'Absent-mindedness factor' apart, I remember a friend of mine who had a NiMH pack on his Multiplex TX. When the batts began to give out, the TX uttered 2 'bip' (and when I mean 2, I mean 2!...not 10 in binary..), then his brand-new Swift went down like a..Brick*.
So I prefer the PITA of discharging/charging my NiCads each time I go to fly and tossing them into the (proper) litter basket once a year.
....Shhhhh!! dont'tell anyone, but at the moment I have a NiMH pack on my TX ...but that's only a temporary arrangement due to the fact my supplier hadn't NiCads on the size/capacity I wanted....

...may the Charge be with you, guys.

Cheers,
Marco aka Leo
Leonardo is offline Find More Posts by Leonardo
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Battery servo question msduk Mini Helis 3 May 08, 2006 12:32 PM
battery charger question on Sky Scooter Pro LuckyArmpit Beginner Training Area (Aircraft-Electric) 14 Jul 08, 2001 08:36 PM
Probably a dumb battery charging question... Dennis Fenrick Power Systems 4 Jun 20, 2001 05:53 PM
Battery charger question for a Zagi 400X Josh C Foamies (Kits) 1 Jun 05, 2001 11:31 PM
Charging my battery??? Embarrasing question :) garyc Beginner Training Area (Aircraft-Electric) 6 Jun 01, 2001 02:39 AM