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Old Sep 13, 2012, 11:36 AM
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FlyingW's Avatar
Long Valley, NJ, USA
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Two Nanos for a Big Plane - Two Rx Batteries?

I'm finishing up a Four Star 120 and plan to use two Nanos to get enough channels to have a four servo wing (flaps and ailerons), rudder, elevator and throttle.

I have a 2x2300mah 6.6v A123 pack that I can use for Rx and servo power. I was thinking as an alternative I could use two 2x1100mah A123 packs - one on each Rx. Perhaps providing a degree of redundancy.

Are there any problems with this approach?

Please advise. Thanks,

Paul
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Old Sep 13, 2012, 12:42 PM
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I did something similar on my 38% Extra, but I did not run the two nanos on two separate batteries. I hooked up the two batteries in parallel, and powered both Nanos that way. As long as they were identical batteries with the same mAh rating, it is working just fine.
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Old Sep 13, 2012, 05:45 PM
Xtreme Power Systems
Lake Havasu, AZ
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We run one battery to the 1st receiver, and another battery to the 2nd receiver - and we put a jumper (female-female servo lead) between both receivers. If either battery fails, power will pass through to both receivers. You could also run both batteries in parallel directly.
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Old Sep 13, 2012, 07:29 PM
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FlyingW's Avatar
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Thanks Jim, and Uff-Da RC.

I didn't think about the jumper between. Very interesting setup.

Take care,

Paul
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Old Sep 13, 2012, 10:16 PM
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Originally Posted by JimDrew View Post
We run one battery to the 1st receiver, and another battery to the 2nd receiver - and we put a jumper (female-female servo lead) between both receivers. If either battery fails, power will pass through to both receivers. You could also run both batteries in parallel directly.
How would you know if a battery failed. I certainly wouldn't fly again until the problem was fixed.
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Old Sep 14, 2012, 12:29 AM
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Son, Norway
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Originally Posted by Uff-Da RC View Post
As long as they were identical batteries with the same mAh rating, it is working just fine.
They don't need to have the same capacity, only voltage.

It's a good idea to use a diode inline with each pack, as some batteries fails shorted and will take out the other one too.

Fred
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Old Sep 14, 2012, 08:13 AM
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Fred,

Can you please elaborate on this battery and diode design? Over the years I've heard about doing this years, but it hadn't yet applied to me - now it may apply and I want to understand it.

Thanks,

Paul
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Old Sep 14, 2012, 10:09 AM
Xtreme Power Systems
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How would you know if a battery failed. I certainly wouldn't fly again until the problem was fixed.
We run a Tattletale on the bus of each receiver. If there is a problem, we know it!

The diode setup prevent voltage from flowing the opposite direction (short).
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Old Sep 14, 2012, 11:19 AM
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Originally Posted by FlyingW View Post
Fred,

Can you please elaborate on this battery and diode design? Over the years I've heard about doing this years, but it hadn't yet applied to me - now it may apply and I want to understand it.

Thanks,

Paul
A short in one battery will not drain the other one. If level of charge is different, the high pack will not "charge" the other one.
Take a look here.
Note that charging needs to be done on the battery side of the diode, for instance via balancing connector.

Fred
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Old Sep 14, 2012, 06:58 PM
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Long Valley, NJ, USA
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I understand. Thanks,

Paul
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Old Sep 16, 2012, 09:36 AM
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Quote:
Originally Posted by JimDrew View Post
We run one battery to the 1st receiver, and another battery to the 2nd receiver - and we put a jumper (female-female servo lead) between both receivers. If either battery fails, power will pass through to both receivers. You could also run both batteries in parallel directly.
As an alternative, take a look at the Fromoco Wolverine switch. I have been using them for several years on big birds and turbines to power two receivers with two batteries. http://www.fromeco.org/products/04frcwo-430b/
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Old Oct 05, 2012, 09:11 PM
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The big Four Star had her successful maiden this afternoon. It was a bit inconvenient making the power lead connections but I think the arrangement can be improved.

In the current arrangement I made up a custom 16ga cable with an Astroflight zero loss connector on the battery end. The cable is about 12 inches long. There are two pigtails with 22ga JR-type plugs at the receiver end.

I want to put a high-quality switch in there somewhere so I can leave the plugged connections made while the plane is assembled at the field.

At jblloyd's excellent urging I looked at the Fromeco Wolverine switch - cool product, however; I think it may be overkill for my application since I'm using only one battery. I looked at Fromeco's Badger switch as a possible alternative:

http://www.fromeco.org/Products/04FRCBADSW-420b/

One Badger option has 16ga wire as the input from the battery, and two JR plugs out towards the receiver (just like my custom cable). Fromeco's intent for this arrangement is to plug both JR plugs into a single receiver to deliver double the power.

My arrangement is slightly different in that I have two receivers. The nano in the fuse has two servos - rudder and elevator, both HS-5645s. The nano in the wing has four servos - ailerons HS-635s and flaps HS-645MGs.

I had one flight with the basic cable and pigtails and it worked fine with several full flap landings.

Here is the question: Do you think that the Fromeco switch acts equivalently to the basic cable and pigtails? I guess the question comes down to whether or not the Badger with its two 3-amp JR plugs can deliver enough power to each nano.

What is your opinion?

Thanks,

Paul
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Old Oct 06, 2012, 01:29 AM
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products like the Badger switches protect against battery failure, specifically shorting. Most batteries fail open circuit, so if you have two packs in parallel, one failing and going open circuit it will be fine. But it basic parallel connection and one fails and shorts, it will hose the second pack.

Battery share will also make sure both packs are drained at the same voltage, can use different capacity packs, etc.

What size/type of plane is it you're flying?...
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Old Oct 06, 2012, 07:36 AM
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Four Star 120. 11 pounds, 12xA123 cells. Sport flyer.
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Old Oct 08, 2012, 01:34 PM
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Originally Posted by FlyingW View Post
Four Star 120. 11 pounds, 12xA123 cells. Sport flyer.
two three amp plugs should be fine. if you want a little bit of headroom, you can solder an extra Y or two to add an extra plug.
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