Question after maiden flight

jcjrogers · Posted: Sun Jan 15, 2012 9:56 am Post subject: Question after maiden flight

I'm a newbie with a question after the maiden flight of my new FP helicopter (Blade 120 SR).

How can you tell how long to run the battery? The problem is, I'm mainly hovering, and spending most of my time re-setting the copter. Simply, for every 30 seconds of flying time, I'm spending minutes in non-flying time. Today, I changed batteries when the power loss became noticeable, which I know is too late. Any suggestions?

nick_onelove · Posted: Sun Jan 15, 2012 11:37 am Post subject:

To truly tell you would need a more advanced charger in order to check the battery's voltage before and after flight.

For now just set a timer for 5 minutes.
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Align: Trex 250 3GX + Trex 450 Pro with Vbar
Blade: 450 X, mCP X, 120 SR, mSR X, CX3, mCX2
Esky: Belt-CP X and V2 - Futaba: Heli-Max Axe 400
Walkera: V500D01, M120D01, V100D08, DEVO 8
Spektrum: DX8 - AMA #967873 - IRCHA #4095

jcjrogers · Posted: Sun Jan 15, 2012 12:18 pm Post subject:

Problem is, right now 5 mintues of real time might be only 1 minute of flight time. Any other way to guage?

Also, are the timers on the more sophisticated 6-ch, etc. txmitters simply just stop watches, or do they run only when the throttle on the txmitter is engaged?

tombo242 · Posted: Sun Jan 15, 2012 9:34 pm Post subject:

Most Tx timers are just an alarm system that starts when you press the button and sounds when the time is up. Usually we take flight time from when the battery is plugged in or the first throttle advance. Even when it is not in the air the heli is still drawing some power from the battery.

Tom.
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jcjrogers · Posted: Sun Jan 15, 2012 10:40 pm Post subject:

Oh wow, then I'm getting 30 minutes or so out of each of my batteries! I guess another way to do is to is to use the stopwatch on my phone and just stop every time the copter goes down. I hear you about the draw, but while idle, the draw has to be a fraction of what it is when actually running. I figure the lost time picking-up or laying-down the phone after a crash or before a take-off, would likely compensate for the draw caused by the idle copter. In other words, 5 minutes on my phone's stopwatch, might equate to only 4 minutes or so of actual flight time.

As far as txmitter timers are concerned, can you start and stop or does stopping always reset? In other words, could I do as I've described with a transmitter timer?

nick_onelove · Posted: Sun Jan 15, 2012 11:30 pm Post subject:

The DX8 has a timer that can be programmed to start and stop according to throttle position, but be careful with those 30 min flights, Tom is absolutely right about the idle draw. I once got my 120 SR stuck way up in a giant redwood and when the wind blew it down about 45 min later the battery was all puffed up; completely toasted.
_________________
Align: Trex 250 3GX + Trex 450 Pro with Vbar
Blade: 450 X, mCP X, 120 SR, mSR X, CX3, mCX2
Esky: Belt-CP X and V2 - Futaba: Heli-Max Axe 400
Walkera: V500D01, M120D01, V100D08, DEVO 8
Spektrum: DX8 - AMA #967873 - IRCHA #4095

chopper54 · Posted: Mon Jan 16, 2012 2:52 am Post subject: post subject

The DX6i timer is started with the trainer switch which is spring loaded. To reset the timer you pull and hold the switch for 3 seconds. The count down can be paused with a flick of the switch and restarted the same way.
It is a feature i use now and again but only for seconds, not minutes.
Your best bet is to get more batteries and and swap them when time is up. If you have only used half the battery power it will charge back up in half the time. The best way for more flight time is allways more batteries.
You can soon shorten the working life of a lipo if you abuse them.

tombo242 · Posted: Mon Jan 16, 2012 7:53 am Post subject:

Hi JC,

Re Current draw: Here's a pic of my mini Spitfire just sitting on the desk with no prop or servo movment. I do know that it is not a heli but it draws less current than my micro helis. (I don't have a pic on line of that.)

As you can see it is drawing 0.05A, that's 50mA, your stock battery is 500mAh so with a max of 80% safe discharge you have 400mAh available. If your battery is fully charged and your current draw is as low as this one (unlikely), then your battery will be at the danger level in 8 hours with no flight at all. However, in hover the current drawn with a micro heli can easily be 3.5 or more amps so total continous flight time would be 400mAh/3500mA = 0.114 hours or 6.84 minutes, more or less depending on flight characteristics.

You can see that without putting your heli on a test rig and checking power drawn under all possible conditions (a fast vertical climb could easily push the current beyond 6A, while translational lift in ground effect could reduce it considerably) there is just no way to predict battery safe connection time. All you can say is that the further you advance the throttle the shorter the safe time in the air becomes.

Incidentally, the timer on the DX6i can be programmed to the 'throttle cut' or 'trainer' switches or just inhibited.

Tom.
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Dumb Thumbs · Posted: Mon Jan 16, 2012 9:32 am Post subject:

The 120SR (great little heli IMO) has a very good LVC (low volt cutoff) built in. While it's not a good idea to always fly till the LVC kicks in, it won't kill the battery if you hit that cutoff once in a while.
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jcjrogers · Posted: Thu Jan 19, 2012 1:26 am Post subject:

Thanks for all the help and information guys. I've been using my cell phone timer while practicing hovering with just a little additional movement in my den. Now that I'm getting everything down pat, the flights are getting longer and the time between flights is getting shorter. I have two 550mAh batteries plus the 500mAH, which came with the copter. I'm using all for 5 minutes according to my cell phone timer (probably averaging 4.5 minutes of flight time over maybe 10 - 12 minutes tops of real time).

I'm not familiar with the LVC on the 120 SR. Is this just something that shuts the copter down when the battery gets to that point? If so, that has never happened. The first day I was flew (just hovered), I felt like the copter was growing "weaker" so I would swap batteries. Since that day, I've used my timer method.

nick_onelove · Posted: Thu Jan 19, 2012 1:56 am Post subject:

The LVC has a soft cut-off; that loss of power you noticed was it.
_________________
Align: Trex 250 3GX + Trex 450 Pro with Vbar
Blade: 450 X, mCP X, 120 SR, mSR X, CX3, mCX2
Esky: Belt-CP X and V2 - Futaba: Heli-Max Axe 400
Walkera: V500D01, M120D01, V100D08, DEVO 8
Spektrum: DX8 - AMA #967873 - IRCHA #4095