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Old Dec 02, 2010, 09:02 AM
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How do I know for how long I can fly?

Hi. I'm new to RC flying and I haven't got my plane yet, but I want to ask one question in advance.

I ordered a Zippy Flightmax 2200mAh lipo battery, so my main concern is that, if I fly for too long, emptying the lipo completely, will the lipo get damaged?

So my question is, should I take the time I fly? I mean, it's sometimes cold weather so the flight time cant be accurate... how do you know when to stop?

Any ideas?
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Old Dec 02, 2010, 09:18 AM
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United States, NY, Syracuse
Joined Oct 2008
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After a while you can get a general feel for how long a certain plane will fly on how much battery pack it has. But, ultimately it will come down to trial and error. First thing you really need is a charger that tells you how much capacity has been "replaced" when charging. What I do is take a new plane out and fly for 5 minutes and then go charge it and see how much capacity it takes to get back up to full.

So say I had a 2200 mAh pack like yours and after 5 mins it took 1200 mAh to charge up... that means that there was 1000 mAh of capacity left.

You can probably safely take the pack down to about 10% of it's capacity, which would be 220 mAh

So you have 1000-220 = 780 mAh of safe capacity left in the pack after 5 mins.

If 1200 mAh = 5 mins, then 780 mAh = (780/1200)*5 mins = 3.25 mins, which gives you 8.25 mins of total flying time when combined with the initial 5 mins.

I might take the plane up for 7 mins the next few times and record the amount it takes to charge to get an average max flight time... I like to set my flight timer to a minute or two before that time is up so I have time to line up for a landing or two.


To answer your other question, if you fly in cold weather, just make sure that the pack is somewhere warm before you plug it into the plane (like in your pockets or something). As long as the pack is not too cold before plugging it in, it will keep itself warm enough in flight to not worry about it. Flight times shouldn't be any different in the cold if this precaution is taken.
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Old Dec 02, 2010, 09:26 AM
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Thanks for the answer ChillPhatCat, however it was a bit confusing answer to a beginner like me p

Let's say I do some mis-calculation and the plane suddenly runs out of power.. is it guaranteed that my lipo is damaged?

Are there any good general "thumb of rules" that I can follow? )

Check the voltage of the lipo before taking off would be one right?

Fly for 5-10 minutes and check the voltage again, etc?
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Old Dec 02, 2010, 09:52 AM
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If your ESC has the appropriate LVC(low voltage cutoff) for the battery type and voltage. the ESC will cut power to the motor before damage is done to your battery.
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Old Dec 02, 2010, 09:58 AM
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Originally Posted by Cam Galbraith View Post
If your ESC has the appropriate LVC(low voltage cutoff) for the battery type and voltage. the ESC will cut power to the motor before damage is done to your battery.
Ok thanks! I've bought the AXN floater, it has some 20A ESC, not sure what brand.

I also bought the Turnigy Plush 30A speed controller. It does not seem to indicate any LVC, at least not on:
http://www.hobbyking.com/hobbyking/s...ller&aff=62207

Any ideas?
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Old Dec 02, 2010, 10:14 AM
Fueled by Arabica Beans
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United States, NY, Syracuse
Joined Oct 2008
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Quote:
Originally Posted by raRaRa View Post
Thanks for the answer ChillPhatCat, however it was a bit confusing answer to a beginner like me p

Let's say I do some mis-calculation and the plane suddenly runs out of power.. is it guaranteed that my lipo is damaged?

Are there any good general "thumb of rules" that I can follow? )

Check the voltage of the lipo before taking off would be one right?

Fly for 5-10 minutes and check the voltage again, etc?
LiPo's seem to fall off really fast once you get them down to a certain point. The only protection in case you do fly too long are the low voltage cuttoff's as Cam said:

Quote:
Originally Posted by Cam Galbraith View Post
If your ESC has the appropriate LVC(low voltage cutoff) for the battery type and voltage. the ESC will cut power to the motor before damage is done to your battery.
That turnigy speed controller is programmable, you can program it (a little harder and I don't know the procedure) with your radio, or with a seperate programming card like this one: http://www.hobbyking.com/hobbycity/s...idProduct=2169.
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Old Dec 02, 2010, 10:15 AM
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Most LVC's are a little under the recc'd safe lowest voltage of Lipo ... but basically the default setting will save the battery.

I submit that most recc'd set-ups of motor / ESC / battery pack are designed around the 8 - 10min duration with average flying.

Therefore either get a digital timer or if Tx has a timer facility set it at 6 mins .... when alarm goes of - bring it round and land. When charging as another says - you should see how much is used out of pack ... you may be able to up that time to 7 mins or more.

But I also submit that many people start to look at landing after 5 - 6 mins anyway ... that is general club / sport flyers.
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Old Dec 02, 2010, 10:47 AM
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Joined Apr 2008
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You can calculate until you're blue in the face but variations in how you fly from flight to flight will affect the run time a lot. This goes for both electric and glow people: Just be conservative on your first flights. 2-3 minutes. When you recharge you can calculate what percentage of the battery you used. i.e. If you flew 3 minutes and when recharging the battier you find it was still half full you know you could have flown 6 minutes. After you do this several times and increase your flight time you'll have a better idea.
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Old Dec 02, 2010, 10:47 AM
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Possum Kingdom Lake, TX
Joined Oct 2008
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here is what I do:

This is, in no way, a scientific method, but it has worked great for me. If your ESC has a low voltage cut off, get several packs of the same brand and size. Put a freshly charged pack in your plane, start a stop watch/timer and fly normally (your average style of flying) as you would on a regular basis. Fly until you hit the LVC and land. Take the time from your timer, subtract 30 seconds or so for safety, and set a countdown on your radio.

Now you know about how long you can fly your packs (as long as they are the same size and brand). If you fly really hard on a pack, land a minute or 2 early. If your gliding around a lot, you can add a minute or 2.


Others on here may freak if they hear this method, but I've been doing it ever since I started flying...and have yet to ruin a pack. I have a couple that I've been flying for 2 years now, and still do fine with sport/aerobatic flying


(I don't fly hard 3D, so I'm not sure how well this method would work for that)
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Old Dec 02, 2010, 03:29 PM
Balsa to the Wall
Deep in the East Texas Piney Woods
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I don't like to discharge my packs too low, I prefer to have at least 3.8V per cell left in them when I remove them from the plane. I put a new pack in and , as others do, I fly for 5 minutes and check the voltage. If it shows above that, I adjust the flight time until I reach the target voltage upon completing the flight.
Do you have a Watt meter or some way to test the voltage of your packs? If not, that is one of the best tools you can have in your flight box.


Chuck
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Old Dec 02, 2010, 10:25 PM
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Boise, ID
Joined Dec 2008
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Quote:
Originally Posted by raRaRa View Post
I ordered a Zippy Flightmax 2200mAh lipo battery, so my main concern is that, if I fly for too long, emptying the lipo completely, will the lipo get damaged?
YES, it will. Absolutely. Positively. LiPO batteries should not be flown less than 20% of their capacity. They should be stored at 50%. In a refrigerator. Then charged up to 100% before flying. All this can be found at the Batteries and Chargers forum here at RCGroups, which is a very useful forum for new electric flyers.

By all means, time your flights and finish before LVC, which are often set for less than 20%.

You'll need five things to ensure long life for your batteries: Experience, and good advice from that forum, one of those little $10 voltmeters, a timer, and a good charger. For a charger, I recommend the excellent and somewhat basic CellPro 4S to start with, and if you can, get a more sophisticated one. You can often get a good used CellPro 4S on the For Sale/Wanted forum here at RCGRoups. That's where I got mine.

Although you're using up capacity, you can measure it indirectly with voltage. We actually charge up these "3.7 volts per cell" LiPO batteries to 4.2 volts per cell, for 100%. At about 50%, the voltage will be about 3.83, and at 20% the voltage will be about 3.7.
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Old Dec 03, 2010, 01:05 PM
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Something like this is really your best bet for knowing where your batteries are at, they're quick and easy to use and you don't even have to remove the battery from the plane to check it.
http://hobbyking.com/hobbyking/store...idProduct=6589

I never saw the need until i got one, and now I use it all the freakin' time!
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Old Dec 03, 2010, 01:47 PM
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Boise, ID
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Yep, That gizmo is the "little $10 voltmeter" I was referrring to. Thanks wavo.
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Old Dec 03, 2010, 01:58 PM
Fly lower!
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West Texas
Joined Jan 2005
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You might want to consider this one from hobby city. It is much more accurate, tells you the total voltage of the pack, and the difference between batteries, as well as the voltage of each individual cell, up to 6 cells. Well worth the extra money.

http://www.hobbycity.com/hobbycity/s...idProduct=8927

I used the less expensive ESC for awhile, and even had two, but one day compared the total voltages, and there was a huge difference. the BM-6 model is much more accurate.

Just my thoughts and experiences. aerolite
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Old Dec 03, 2010, 03:55 PM
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Norway, Hordaland, Årstad
Joined May 2009
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Quote:
Originally Posted by raRaRa View Post
Hi. I'm new to RC flying and I haven't got my plane yet, but I want to ask one question in advance.

I ordered a Zippy Flightmax 2200mAh lipo battery, so my main concern is that, if I fly for too long, emptying the lipo completely, will the lipo get damaged?

So my question is, should I take the time I fly? I mean, it's sometimes cold weather so the flight time cant be accurate... how do you know when to stop?

Any ideas?
---------------
With the AXN floater jet/aka clouds fly, your problem will not be the flight time, it will be that you bought a way too big battery for it. For a beginner especially, keeping the weight low is important, and a 1300mah battery will easily give you 10 minutes flight time on that plane, unless you have changed out the stock engine.
I'm not saying the plane can't fly with a 2200mah lipo, but there is no need to make the plane too heavy just to extend flight time. You can always land and switch battery, and you have better chance of successful landings with a smaller lipo.
I'm thinking that you have a 3cell battery, in case it is 2cell it is too weak, but not too heavy...
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