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Spektrum RX power rail question

Old 10-15-2009, 12:08 PM
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Eganwp
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Default Spektrum RX power rail question

Hey guys,

Quick question regarding an AR7000 Spektrum RX. Can anyone confirm if the power rail is CONNECTED from the battery port as well as the other ports (ie AUX2)? There is a lot of speculation and discussion from what I've seen like here: [link=http://www.rcuniverse.com/forum/m_8952708/mpage_1/key_/tm.htm]http://www.rcuniverse.com/forum/m_8952708/mpage_1/key_/tm.htm[/link]

Reason I'm asking is I want to confirm that if I run dual A123 1100 batteries plugged into separate ports that the RX will draw from each battery EQUALLY, and not just from the BATT port until dead and then the AUX2 port. If that's the case then I will have to move to a 2300 A123 main and an 1100 secondary.


Can someone confirm who has checked and tested? Thanks!

Eganwp
Old 10-15-2009, 12:28 PM
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Cobra1
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Default RE: Spektrum RX power rail question

I have never opened it up to look inside but I run my battery into one of the open channels and everything works as it should. The battery slot is just harder to get to so i don't use it. I always just thought it was separate just because of the binding function.
Old 10-15-2009, 02:01 PM
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Eganwp
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Default RE: Spektrum RX power rail question

But you're just using 1 of the other channels and not both correct? If so that doesn't really help me as I know it will work when just using another channel.

I just want to know if it will concurrently draw power from both channels or switch when battery channel loses connection or battery dies. Somebody's gotta know this as I'm sure a majority of people here are using dual batteries and Spektrum RXs...
Old 10-15-2009, 02:39 PM
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JoeAirPort
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Default RE: Spektrum RX power rail question

Well the guy in thread you posted did test it and made his claim. Don't you believe him? Asking here you're going to get the same level answer (from a forum member). You should probably call Spectrum tech support.

I've been running the AR7000 in two 50cc aerobats all summer thinking that I was drawing from two JR output extensions on my Smart Fly Super switch. You certainly having me thinking. The only way for me to be sure would be to tear apart my radio gear and measure current on both switch output extensions. But I don't think I want to undress all my wiring.

Edit: I just spoke with MJ on Horizon Hobby's tech support. He says the battery port and all servo ports draw power and they are all on the same power rail.
Old 10-15-2009, 03:44 PM
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Jake Ruddy
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Default RE: Spektrum RX power rail question

Well I am not sure where this comes from... but I have run 2 packs on a 921 and they drain evenly every time. Can't see why the 7000 would be different.
Old 10-15-2009, 03:54 PM
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Default RE: Spektrum RX power rail question

For sure.

Only reason I questioned it is that I didn't link the other threads where people have had arguments on the issue. So I'm entirely sure who to believe on this issue...

One easy way you could test would be to simply fly a flight (if running dual RX batteries and ports) and measure the used mah on each pack to see if it's using both or just one. The only issue with that is that some people have also speculated that Spektrum rx's have built in voltage monitoring on the rail and will jump to whichever channel is giving the highest voltage reading... Thus the only way to test that would be current draw.

Anyways, if anyone has any answers that would be helpful I'd be grateful. It really will determine my RX battery setup!

Eganwp
Old 10-15-2009, 03:55 PM
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Default RE: Spektrum RX power rail question

ORIGINAL: Jake Ruddy

Well I am not sure where this comes from... but I have run 2 packs on a 921 and they drain evenly every time. Can't see why the 7000 would be different.
Thanks Jake. I was pretty sure the 9000 series did so, however most people are arguing over the issue on the 7000 and under RX's.



Edit: Thanks Joe, I see you talked to him to find out. I'm going to do some testing on current draw this weekend just so I'm 100% positive for my own peace of mind. Then I can also take it apart and see if the rail is combined on all channels or not as well.
Old 10-15-2009, 06:47 PM
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Default RE: Spektrum RX power rail question

Let me ask this.

If you check the packs before you fly, who cares about a few Mah?

I mean, the second battery is really for redundancy more than anything IMO
Old 10-15-2009, 06:56 PM
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Default RE: Spektrum RX power rail question

It matters. JR plugs are only good for 3 amps. They become the bottle neck with a bunch of high torque servos (5x7955's, 1x5985). So all you can get is 3 amps to that receiver if they only draw off one port. Not good.
Old 10-15-2009, 07:08 PM
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Default RE: Spektrum RX power rail question

Its a power bus, it will draw off both, I just don't think it needs to be dead even.

Again, just my humble opinion
Old 10-15-2009, 09:19 PM
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Default RE: Spektrum RX power rail question

He's not talking about a little bit like you are. He said it will draw nothing off the 2nd battery until the 1st one on the battery port goes dead. That's what I understood. But I don't believe it. Horizon says it draws off both just like any other receiver. I called them. If someone has a spare AR7000 I'll rig up a test and measure current from both ports while some servos are connected. I just don't want to take mine apart.
Old 10-16-2009, 02:56 AM
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freeair
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Default RE: Spektrum RX power rail question

the AR-7000 comes with 1 only battery port , the 921 comes with 2 battery ports. you can still run dual battery packs on the 7000 by using battery port and aux 1 or 2 .
Old 10-16-2009, 06:23 AM
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Default RE: Spektrum RX power rail question

I run dual batteries. One Y'd into the rudder servo, one into the throttle. The battery port is for the flight log as it should be. each battery take the same MAH after each flight. End of problems.

m.
Old 10-17-2009, 07:00 AM
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Default RE: Spektrum RX power rail question

It will work fine as Jake pointed out, but hear is a suggestion for you. Add another reciever, switch, bind both, and have total redundincy. AR7000 are 85 bucks and a good switch is 20, so for a 100 bucks or so, get the picture?
Old 10-17-2009, 10:23 AM
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Jake Ruddy
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Default RE: Spektrum RX power rail question

ORIGINAL: captain stowed

I run dual batteries. One Y'd into the rudder servo, one into the throttle. The battery port is for the flight log as it should be. each battery take the same MAH after each flight. End of problems.

m.

I really would't Y it into your rudder servo because it draws a lot of juice and is used a lot. Now you have 1 3amp connector feeding your rudder and battery to the entire plane.

You only need to use the flight log for a flight (two if you need to move things) after that pull it out and forget about it. Use the battery / data port for a full time battery.

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