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A word about Receiver Batteries for Glow-To-Electric Conversions

Old 11-13-2015, 03:55 AM
  #1  
guapoman2000
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Default A word about Receiver Batteries for Glow-To-Electric Conversions

Hello guys,

I am very aware that this is not the Battery Section, however, I almost got in a situation that might have gone wrong (disaster) with selecting a Ni-MH battery. Not so much that I was using powerful Digital servos on my Glow-To-Electric conversion but, it was a Ni-MH that had been stored and made a few years ago.

I am so happy that I had activated the model to test the setups of the servos and during which time after perhaps 10 minutes the model just quit responding.

At first, I had thought it was my Radio and to my shock and horror, it was this lightly used Ni-MH receiver pack!

Here is a must see video:
https://youtu.be/ow4VmOwIdYA

Stay safe and Happy Landings!
Carlos
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Old 11-13-2015, 12:31 PM
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Bald Paul
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I'm sure there are a lot of flyers who don't think about the current demands of the digital servos. They see 'faster, higher torque' and just get them.

I see the price, and stick with my old standards. Besides, my flying is slow and relaxed (for the most part, anyway, with brief periods of panic thrown in now and then) so I really have no need for them.

One of the other pitfalls for glow to electric conversions (especially for those just making the switch) is not realizing that the ESC they are installing cannot supply enough power for the standard-sized servos. They think they can just remove the Rx pack and rely on the BEC instead. They usually discover their error in the post-mortem of the crash debris.
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Old 11-13-2015, 01:27 PM
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firemanbill
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Best tool you can have for receiver batteries...

http://www.horizonhobby.com/digital-...ltmeter-han171

Voltage load tester. I wouldn't trust a Nimh that is over a couple seasons old. I've had a couple of Nimh packs that have dropped cells in them. Like a bad car battery they will charge and hold their voltage but as soon as you put them under load they will drop like a rock to 1 or 2 volts.

I lost a 1/4 scale Pilot One Piper PA-12 to that very thing. battery checked fine that morning, 3rd flight of the day it just stopped responding mid flight. Post crash analysis revealed a bad receiver pack, when put under load it would drop to less than 2 volts. I was sick to my stomach that day. $800 plus plane lost to a $20 receiver pack.
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Old 11-13-2015, 01:39 PM
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Roberta
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Good discussion and suggestions.

Roberta
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Old 11-13-2015, 04:16 PM
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You might be surprised at the current demand of your servos in flight....

I MAXED OUT one of these with a .90 glow model using 6 NON-DIGITAL servos.

(Should still be available via CommonSenseRC )


https://www.dimensionengineering.com/products/servosense-plus

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Old 11-13-2015, 05:48 PM
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guapoman2000
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Originally Posted by firemanbill View Post
Best tool you can have for receiver batteries...

http://www.horizonhobby.com/digital-...ltmeter-han171

Voltage load tester. I wouldn't trust a Nimh that is over a couple seasons old. I've had a couple of Nimh packs that have dropped cells in them. Like a bad car battery they will charge and hold their voltage but as soon as you put them under load they will drop like a rock to 1 or 2 volts.

I lost a 1/4 scale Pilot One Piper PA-12 to that very thing. battery checked fine that morning, 3rd flight of the day it just stopped responding mid flight. Post crash analysis revealed a bad receiver pack, when put under load it would drop to less than 2 volts. I was sick to my stomach that day. $800 plus plane lost to a $20 receiver pack.

Super recommendation! Thanks for the link on the device!
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Old 11-13-2015, 06:42 PM
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kyleservicetech
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Default More stuff on Nih receiver packs

Originally Posted by guapoman2000 View Post
Hello guys,

I am very aware that this is not the Battery Section, however, I almost got in a situation that might have gone wrong (disaster) with selecting a Ni-MH battery. Not so much that I was using powerful Digital servos on my Glow-To-Electric conversion but, it was a Ni-MH that had been stored and made a few years ago.

I am so happy that I had activated the model to test the setups of the servos and during which time after perhaps 10 minutes the model just quit responding.

At first, I had thought it was my Radio and to my shock and horror, it was this lightly used Ni-MH receiver pack!

Here is a must see video:
https://youtu.be/ow4VmOwIdYA

Stay safe and Happy Landings!
Carlos
Ah yes, the Nih AA sized battery pack issue in our model airplanes.

There has been a lot published in these web sites on using those AA Nih battery packs for receiver power on our RC models, especially the larger models.

Two years ago, I stopped a club member that was going to fly a maiden flight on a kerosene powered turbine model with a 5 cell Nih pack. Told him NOT A GOOD IDEA!

I've conducted dozens of tests on various club members AA sized Nih battery packs, both four and five cell units on my Western Mountain CBA battery analyzer.

Those 5 cell Nih Packs are OK for the smaller models with four low power servos, and ailerons, elevators, and rudders an inch wide. Now, we've got models where the aileron is 1/4 the width of the entire wing, with high power servos to match.

I've got two giant scale models that each use 7 Hitec 645MG servos. Just spinning the transmitter sticks round and round, I've measured peak currents of 14 Amps on my $$$$ Fluke 87V digital meter on its peak hold function.

Putting a 14 Amp load on a five AA cell type Eneloop battery results in its voltage dropping down to 3.5 Volts almost instantly.

IMHO, if there ever was a perfect battery type for receiver/servo power, that would be those A123 2500 Mah batteries. Overload one of those A123's with a dead shorted servo, and the A123 pack will burn up all the servo wiring before it finally quits. (That happened several years ago at a local fun fly.)

Here is a bit of info on the subject:

Analog and Digital Servo Tests
http://www.rcgroups.com/forums/showthread.php?t=2433116

Rant on using 4 cell Nih Packs
http://www.rcgroups.com/forums/showthread.php?t=2431435

Spektrum Voltage Sag Tests
http://www.rcgroups.com/forums/showthread.php?t=2351423

More Info
http://www.rcgroups.com/forums/showthread.php?t=2350982

More and more of my club members are going to those 2500 Mah A123's for receiver power. They far outlast the Nih packs, with some of my 100 plus A123 cells going past five years and still going strong. (FYI, I'm pulling 40 Amps out of some of those cells, with one model pulling 80 Amps out of a 12S2P A123 pack on a giant Big Stick model.)

Ready Made A123 Packs: (SKU Number: RRC2S2500)
http://www.radicalrc.com/category/A123-Cells-Packs-199

Raw A123 cells (I"ve purchased over 50 cells from here, nice place to do business with.) Buy 10 or more, their price drops to $9.30 per cell, or $18.60 for receiver power.
http://www.a123batteries.com/product-p/anr26650m1-b.htm

Soldering these cell requires a high powered soldering iron. I've been using a Weller 100 Watt temperature regulated iron along with Radio Shack Rosen flux to solder these cells.

And, building up your own A123 packs for those interested in doing so:
http://www.wattflyer.com/forums/showthread.php?t=67896
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