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Reciever/Servos Battery

Old 07-14-2020, 04:33 PM
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Dalyn
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Default Reciever/Servos Battery

What mAh battery do you use for your receiver battery? I have a .46 size Avistar Elite and have 5 servos (soon will be 7 because I want to add flaps) and my battery is low after about 10 minutes of flight. Im using a 2000 mah battery pack right now.
Old 07-14-2020, 07:43 PM
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perttime
 
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2000 mAh pack is low after 10 minutes, just running receiver and servos? That doesn't sound right.
- Something wrong with the battery?
- Something wrong with determining that it is low?
- Something using more power than it should?
Old 07-14-2020, 07:44 PM
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jester_s1
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You should be able to get 20 flights on that pack with that plane.
How are you measuring it to know it's low? Either your measuring method is off, your pack is bad, or your charger is bad.
Old 07-15-2020, 02:25 AM
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Test your battery pack the old fashion way, which I still use. Set up your airplane in TV room. Run the system for 10 minutes while you watch TV. Take a break then do it again. I do 3 ten minute runs. I still have plenty of battery left. This works for me since I just charge and fly. Not too high tech.
Old 07-15-2020, 05:58 AM
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Dalyn
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Originally Posted by ETpilot View Post
Test your battery pack the old fashion way, which I still use. Set up your airplane in TV room. Run the system for 10 minutes while you watch TV. Take a break then do it again. I do 3 ten minute runs. I still have plenty of battery left. This works for me since I just charge and fly. Not too high tech.
I have one high torque servo for my rudder and nose wheel. Idk if that would do it or not. I'll test it manually and see what happens.

Originally Posted by jester_s1 View Post
You should be able to get 20 flights on that pack with that plane.
How are you measuring it to know it's low? Either your measuring method is off, your pack is bad, or your charger is bad.
I have a power meter on the side and it was showing yellow after one 10 or 15 minute flight.
Old 07-15-2020, 06:22 AM
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jester_s1
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Is it a Voltwatch meter?
If so, yellow isn't a problem if it's flicking down to it when you are working the sticks. You didn't say what type of battery it is (NiCd, Nimh, LiFe, etc) but regardless of type all batteries drop a noticeable amount of voltage early on, then get fairly level, then drop off hard when they are discharged.

The number that matters is voltage under load. If you have a computerized charger with a discharge function, do a cycle test. A new pack will give you close to its rated capacity, and is still a good battery until it's down to about 80%. The cycle test tells you what your battery can actually do under a sustained load. I do this for every new battery pack before installing it into a plane. I've only caught a defective pack once in 13 years of doing the hobby, but it saved me a plane.

To figure out your flight time capacity, take 2 flights and then discharge test your battery. That will tell you how much capacity you used in the flights. Divide that number by 2, and work out how many flights it would take to get to 30-40% capacity. That allows plenty of safety margin. You'll probably find with that plane that you are safe to get in at least 15 flights before recharging, maybe a few more if you're just making circuits.
Old 07-16-2020, 12:41 PM
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Dalyn
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Yes its a Voltwatch meter. I tested it by steadily working the sticks as I don't have a computerized charger. After 10 minutes was on the second light. After 20 it was on the 4th. At 30 it was on the last green light and stayed there for awhile occasionally going down to red when I worked all the servos at the same time. I did it for 50 minutes and there was no noticeable lagging but when I didn't move anything the light would be yellow and when I moved them would flash down to the red. Does it make any difference when theres not a load on the servos like there would be in the air?
Old 07-17-2020, 02:43 AM
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Not familiar with the voltwatch meter. Iím really low tech when it comes to batteries. Iím running store bought LIFE batteries and homemade A123 battery packs. Minimal testing on them.

Here is a discussion on the voltwatch meter. It includes participation by Hangtime owner, I presume. Hangtimes.com makes battery packs and has good info on their website. Hope this helps you out.

Using VoltWatch with NiMH GP3300
Hangtimes Hobbies

Old 07-17-2020, 07:24 AM
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Servos draw the most current when given a quick stick command, which is why you see it flicking down to red when you do. That's normal.
Your battery is probably fine. You just have to understand what a Voltwatch can and can't do for you.

Voltwatches are handy because they show you the voltage that your system actually sees and have a very fast refresh rate. So they will show you voltage drops that a traditional meter would not. That's why it flicks to red when you work the sticks. What a Voltwatch can't do is tell you the condition of your battery or how discharged it is. It also doesn't give you an actual voltage reading, but rather just "caution" or "low." I've owned one in my 13 years doing this hobby, pretty early in the process. I found it enlightening to use, but less useful than other methods of testing batteries. The real value of the Voltwatch is its convenience to do a quick check and look for changes in the way the battery behaves. You can learn what is normal and easily spot what is not.

If you want to use your Voltwatch to tell you if your battery is good, hold a control surface still and deflect the transmitter stick. That will put more load on the system than it will see in flight. Watch the Voltwatch for 2-3 seconds and release (you can overheat your servo motor by doing this too long).

If you want to really know the condition of your battery, spend a few dollars on a computerized charger. The Imax B6 or one the many clones of it is cheap and will work fine. You can do the discharge test that I recommended above and also see how your battery's voltage changes as it discharges under a constant load. To kick it up a notch, date your battery and do a discharge test every 3 months that you write in a log. That will let you spot deterioration and know if it needs to be replaced before it causes you a problem.
Old 07-17-2020, 10:37 AM
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Dalyn
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Originally Posted by jester_s1 View Post
Is it a Voltwatch meter?
If so, yellow isn't a problem if it's flicking down to it when you are working the sticks. You didn't say what type of battery it is (NiCd, Nimh, LiFe, etc) but regardless of type
I had a nicad battery in I also have a NIMH that I haven't used not sure if it would do the same thing or not.
Old 07-17-2020, 12:55 PM
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You didn't say how many cells are in your battery. If it is a 5 cell and you are using the charger that came with the radio to charge it it is not getting a full charge.
We used to fly trainers with 600Mah packs and get 6+ flights on them.

david
Old 07-17-2020, 01:09 PM
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Originally Posted by Dalyn View Post
I had a nicad battery in I also have a NIMH that I haven't used not sure if it would do the same thing or not.
If you are using the stock plug in the wall charger and you have a 5 cell 6v battery you need to leave it plugged in all night before you fly to get it even close to where it should be. It won't hurt it.

But spend the 100 bucks and get a Venom 2 battery charger or spend less and even get the Imax B6 single.
Old 07-17-2020, 02:41 PM
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Dalyn
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Thank for the answers. They are both 4 cells. Do you prefer NIMH or Nicd or what do you use?
Old 07-17-2020, 08:31 PM
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Between those two, NiCd all the way. They are a little bit heavier, but more durable. Buy welded packs with Sanyo cells. Hangtimes Hobbies is a great vendor.

That said, all my flight packs are now LiFe. I buy the soft type LiFe 1400 mah packs for everything but my 50cc Sukhoi 26. LiFe packs are lighter, about 1/2 the price, don't self-discharge, and can handle more current draw. they don't hold up like NiCd's, but I do a 2 year replacement cycle which puts my actual cost about the same as the 3-4 year cycle I used to run with NiCds. I paid $13 at Hobbyking for the charger I use for them.

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