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Old Jan 22, 2013, 04:53 PM
Why kamikaze pilot wear helmet
mikes68charger's Avatar
United States, OH, Columbus
Joined Jul 2010
1,096 Posts
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Power meters on bird

Ok guys we all seen the power gauges that some flyers use to show status of there Nicad Receiver packs

I have converted all my birds to 6.6 life. Are there any meters I can leave on plane to show power level?
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Old Jan 22, 2013, 07:09 PM
Registered User
Australia, VIC, Melbourne
Joined Feb 2010
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Quote:
Originally Posted by mikes68charger View Post
Ok guys we all seen the power gauges that some flyers use to show status of there Nicad Receiver packs

I have converted all my birds to 6.6 life. Are there any meters I can leave on plane to show power level?
You cant tell how full a Life is by its voltage. They stay at 6.6V from about 90% to nearly flat and then drop fast.

Only way to tell is to work out how many flights you get from a pack (do a few then charge and see how much you put back in) and count them.
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Old Jan 23, 2013, 06:42 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,000 Posts
A battery checking tool like the Smart Guard will tell you some of the stuff you want to know:

Smart Guard - Handy battery checking tool - http://www.rcgroups.com/forums/showthread.php?t=1187136

That will show you the pack and cell voltages and give you a little eye candy graph that is sort of useful. It connects to the balancing/charging connector (usually a JST-XH socket with one more hole than there are cells) found on nearly all LiPO batteries.

If you connect an un-recharged pack to the ESC and run the motor up a little with the Smart Guard attached, you'll know immediately if the pack is charged or not. The cell voltages will fall steeply and quickly on a discharged pack and if they get any lower than 3.7V or so after a few seconds at full throttle, the pack is not ready to fly. This assumes that the pack is healthy and not too small for the load you are putting on it.

Meters mounted on planes for battery state at a glance are not too much used with LiPOs as far as I know. All the battery checking is done off the plane and keeping an eye on the recharged capacity and learning your flight durations will keep you out of trouble.

Tell us the sizes of pack or even all of the power systems details and we can offer better advice.

Do you have a watt meter yet? That is the single most useful tool for electric RC. But a decent battery checker is needed too.

Jack
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Old Jan 23, 2013, 10:23 PM
Why kamikaze pilot wear helmet
mikes68charger's Avatar
United States, OH, Columbus
Joined Jul 2010
1,096 Posts
I'm useing 2 2000mah 6.6 life packs each with there own switch. I'm looking for something like those cheap volt meters you see with the light bar that will show info for the life type packs
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Old Jan 24, 2013, 09:31 AM
Jack
USA, ME, Ellsworth
Joined May 2008
17,000 Posts
I really don't understand a power system with switches for each battery. In most cases it is best and safest to employ the act of connecting and disconnecting the battery to determine the on and off state of the entire power system.

Are both packs in use at the same time, in series or parallel? Maybe more details about your power system would help to understand this.

The best way to manage battery capacity is to start a flight with a fully charged and rested battery and fly for the the amount of time (in two or more flights if you like but without disconnecting from the ESC) that will use up about 80% of the battery's stated capacity.

There is some danger in disconnecting a partially used battery and then re-connecting it to your ESC for further flights. If the voltage has fallen when it is reconnected it can lead to the ESC miscounting the cells, letting you use the pack to too low a voltage, and battery damage can take place as a result.

Under load the LiFE cells hold voltage well for most of the time it takes to discharge them. Then the voltage falls quickly just before they are depleted. When that occurs the useful capacity is used up, there is not really enough power left to fly any longer. So what you see on a meter with plane setting on the ground is sort of meaningless.

When you take the load off of the battery (as when it is setting on the ground) the voltage will recover and it will look like there is enough power to fly, when you put a load on it the voltage will immediately drop (faster than the drop you would get from a fully charged pack) and it will be obvious there is not enough power to fly.

What battery pack are you using? We can probably tell you the approximate capacity in mAH you can expect from it. And if you tell us the motor and prop you intend to use or the current (average or peak) that your power system will draw we can tell you about how many minutes of flying time you can expect from it.

But I think your approach is flawed, that meter will not be of any help to you except to tell you anything other than what the present voltage of the pack is. It will not tell you the state of charge or remaining capacity or flying time left on the pack.

There are some gadgets that will display pack and cell voltages, you can see some of those here:

http://www.hobbyking.com/hobbyking/s...cessories.html

Included in those is a battery condition tracker that will let you see (via a radio link) the battery state with the plane in flight:

http://www.hobbyking.com/hobbyking/s..._869_5Mhz.html

And there are various gadgets at that link that will display voltages, use various colors to indicate voltage, or even make various noises at various batter states.

But the bottom line is that it is easiest for you to learn and to know that you have xx minutes of flying time at the start and then fly for that long. In some cases, you can tell by the way the motor responds to throttle that you are nearing the end of a flight and it is time to land. Or you might have a timer on the TX that you can use.

But the meter on the plane is not going to be of much help.

Jack
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Old Jan 24, 2013, 12:39 PM
Why kamikaze pilot wear helmet
mikes68charger's Avatar
United States, OH, Columbus
Joined Jul 2010
1,096 Posts
Ok, wow thanks you gave me a lot to think about. I was just looking for a meter like this that would work for life reciver packs.

http://www.tjshobbies.co.uk/product_...roducts_id=285

But I see it don't mater as it not putting the Life reciver packs under load.

I found this wich is sweet.

http://www.boomarc.com/en/booma-rc-intelliswitch-1

But I don't trust that much tec to make sure my plane has power.

I asked the question as Im building 3 Top Flite Gaints P51, P47 and P40.

Im useing 2 sep 2000mah 6.6 life on there own swiches. This is due to the fact if 1 swich or life recivedr packs fails then You are still ok.

It also helps by providing the reciver power at 2 diffrent points when you have a lot of big servos. (One life is pluged into the batt port, and the othere is connected by a Y harness wich is connected to a channel that is on the othere side of the reciver. ie for a AR8000 The batt port is on the right side of the reciver, then I will put a Y harrness on the Throttle Servo Port wich is slot Number 1 on the reciver on the left side of the reciver)

As life reciver packs are alot lighter than nicads it make sence and adds no exstra weight.

I have a Watt/Amp meter that I use to check my lipos and Life packs I like this meter as it gives you a bar and %. Ie Your life pack is at 6.6volts at 85% capasity.

So I thought there may be a meter like this, but smaller like the one in the first link that peaple have been useing for a long time now and leave them attached to there planes.

I love my Life reciver packs, and now most new Gas Motors (like my DLE55 RA) will take up to a 2s lipo with no issue)

I guess I just will start useing the telemitry with my DX8 more, but Like you said they stay at 6.6 then drop sharply so I guess I could just set a alarm to go off.

Tech keeps change ye
Thanks Mike
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Last edited by mikes68charger; Jan 24, 2013 at 12:48 PM.
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