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-   -   Rx Battery Placement. (http://www.rcuniverse.com/forum/beginners-85/10508949-rx-battery-placement.html)

JBryson 05-08-2011 05:11 PM

Rx Battery Placement.
 
1 Attachment(s)
Is there some rule of thumb as to how close to the rx the rx battery can be? Best rx battery for the spectrum AR 7000 using six DS 821 servos? Plane is a 1/4 scale BUSA Fokker D-VII. Zenoah G-26 for power and an optical kill switch attached to the gear servo location. Will be installing a 2700mAh NiMH for the ignition module. Have the standard 4.8v,1100mAh NiCd that came with the receiver and a 6v 1400mAh NiCd. Any help for this nubbie appreciated. John

ChuckW 05-08-2011 05:21 PM

RE: Rx Battery Placement.
 
I usually use the Rx battery as ballast and put it in a convenient place that helps achieve the proper CG. If that happens to be right next to the RX, it isn't an issue at all.I would run 6 cells with that Spektrum receiver.

RCKen 05-08-2011 05:24 PM

RE: Rx Battery Placement.
 
As Chuck said, placement of the battery in close proximity to the receiver isn't an issue. Heck, you can strap the receiver right on top of the battery if you need to and it won't cause any problems.

Ken

BarracudaHockey 05-09-2011 05:53 AM

RE: Rx Battery Placement.
 
As an FYI about that servo.....

Quote:

•Manufacturer Warning: "Not recommended for planes over 1.20-size or helicopters over .30-size. Loads and vibration in larger models may cause premature failure of the servo, resulting in damage or injury to property and persons
I personally wouldn't run them in a gasser.

billd76 05-09-2011 06:10 AM

RE: Rx Battery Placement.
 
2700 MaH on the ignition??? Be sure that the igntion can handle six volts. The ones I have on my gassers are 5 cell 1500NiMh 4.8 volt NiMh for the ignition and 5 cell 2300 NiMh, six volt for the Rx. six volts will fry some ignitions, or at least it will fry the ones that I own.

RCKen 05-09-2011 06:19 AM

RE: Rx Battery Placement.
 
Bill,
 did you have a typo there??? You state that your ignition is 5 cell 4.8v. If the pack is 5 cell it's going to be 6v.

Ken

Gray Beard 05-09-2011 06:39 AM

RE: Rx Battery Placement.
 
Another heads up. You flight pack battery is nothing I would use in your plane. This is a topic of conversation I just had last week with one of the JR sponsored race pilots. Some years ago when JR/Spektrum came out with there 2.4 systems planes were falling out of the sky way too often. This became known as the BROWN OUT. Then Horizon came out with an on line up-date stating you should be using 6 volt batteries with the new 2.4s. To this day they still give you a 4.8 with any new radio or flight pack. For myself I wouldn't think of flying such a nice big plane with a single 4.8 volt battery pack powering my controls. I would be running two large 6 volts with two switches just to remove the worry factor. Where you locate them isn't a big deal but a single 4.8 sure is. Just me thinking out loud, when I looked at the photos it set off a few bells and whistles. Sorry if I spoke out loud, it isn't my plane.

CGRetired 05-09-2011 08:52 AM

RE: Rx Battery Placement.
 
That's good advice, Gene.

I have parallel 6 volt 1800 mah NiMh packs in my Venus II and my Excelleron 90 (both pattern planes). I have a sign le 1800 mah 6 volt pack in my Skylark, but that may change this year by adding parallel NEW 1800 mah LiFe packs to everything, well, almost everything.. :D

CGr.

RCKen 05-09-2011 09:02 AM

RE: Rx Battery Placement.
 
Dick and Gene,
 While the need for having ample power is always a concern, the brownout issues that plagued early JR/Spektrum systems are pretty much a thing of the past. The problem was that if the receiver voltage dropped below a set level (3.8v if I remember correctly) the receiver would actually "reboot". The reboot on those older receivers took 3-5 seconds and of course that amount of time is an eternity in an RC airplane and would usually result in a crash. Since they have have re-engineered the software so that a reboot now takes less than a second. So if you do get a brownout chances are that you will get control back before the plane crashes.

Like I said, you always want to make sure that you have plenty of juice for the radio on the plane. I just wanted to make sure that the info got out that it's not as big of an issue as it used to be. Other manufacturers have different cutoff voltages for their receivers. I don't know what it is for Futaba, but I know that Airtronics 2.4 systems have a cutoff voltage of 1.8v before the receiver shuts down.

Hope this helps

ken

JBryson 05-09-2011 01:34 PM

RE: Rx Battery Placement.
 
Bill, my 2700mAh is a 4.8 v. What I am now having problems with is the miracle switch I purchased. Each of the switches in the back have two wires and all my spectrum stuff is 3 wire. Wish I knew more about electronic stuff, this drives me nuts!!!!! No problem Grey Beard, think out loud all ya want to. I will use at least the 6v , 1400mAh for the rx and am thinking about the 6.6 v 2100 mAh LiFe packs from LiFeSource also.

RCKen 05-09-2011 01:40 PM

RE: Rx Battery Placement.
 


The switch you purchased will work just fine for turning your Spektrum equipment on and off. For turning on the receiver only the positive and negative leads (black and red on your switch, red and brown on the Spektrum wiring) is used. However, if you need to bind the receiver the switch you have will not work. In order for that to work you will need a Spektrum 3 wire switch. But you can bind directly at the receiver if you need to.

Ken</p>

JBryson 05-09-2011 02:08 PM

RE: Rx Battery Placement.
 
Hey Barracuda, what issues do you have with the DS 821's, the nylon gears or something else? Will the 6.6v LiFe packs have any adverse effects on the rx or servos?

BarracudaHockey 05-09-2011 02:30 PM

RE: Rx Battery Placement.
 
Thats not "my issue", its a manufactuer warning not to use them with large engines or in high vibration environments.

My personal experience is that the output shaft shears off the top of the servo and or the output amplifiers up and die from vibration. Guys that have insisted on using them with 50 size nitro helis have found out the hard way that it's a lot more expensive to fix a crash than to replace a few servos.

Gray Beard 05-09-2011 02:36 PM

RE: Rx Battery Placement.
 
Ken, I was talking with the JR guy and got all the new info on the upgrade but as he showed me, he is still running 6 volts in his planes and wouldn't use the 4.8. As he pointed out to me, the reboot is pretty fast but if it happens when you are too low that one thousand one is still a long time. He also showed me something else he has done sense the advent of 2.4, he makes up his own 6 volt packs but he is using AAA batteries. He was telling me he hasn't had one go down in voltage any faster then the AA packs. He is also a speed racer and every gram counts. He is also telling people to keep there old radio for a while, with all the problems in Japan they are vending things out to be made and he doesn't know to whom. He is also telling the guys to send in there radios for the free upgrade, it really speeds up your radio. I had to sit through all the new JR stuff talk for about an hour but I did find out a lot.

JBryson 05-10-2011 08:38 AM

RE: Rx Battery Placement.
 
I'll be changing the DS 821's for HiTec HS 645MG's, hope these will work as I can't afford the $100 + ea. servos.

BarracudaHockey 05-10-2011 08:57 AM

RE: Rx Battery Placement.
 
They should be fine.

Gray Beard 05-10-2011 09:02 AM

RE: Rx Battery Placement.
 

Quote:

ORIGINAL: JBryson

I'll be changing the DS 821's for HiTec HS 645MG's, hope these will work as I can't afford the $100 + ea. servos.
Should be plenty of power. It's a big plane but as I recall the D-VII didn't do a lot of 3_D. I have been using quite a few of the 5645s and like them a lot. I'm not one of the must have digitals people but if I have a choice I do buy digital. Analog will be just fine for your use.

CGRetired 05-10-2011 01:29 PM

RE: Rx Battery Placement.
 

Quote:

ORIGINAL: RCKen

Dick and Gene,
While the need for having ample power is always a concern, the brownout issues that plagued early JR/Spektrum systems are pretty much a thing of the past. The problem was that if the receiver voltage dropped below a set level (3.8v if I remember correctly) the receiver would actually ''reboot''. The reboot on those older receivers took 3-5 seconds and of course that amount of time is an eternity in an RC airplane and would usually result in a crash. Since they have have re-engineered the software so that a reboot now takes less than a second. So if you do get a brownout chances are that you will get control back before the plane crashes.

Like I said, you always want to make sure that you have plenty of juice for the radio on the plane. I just wanted to make sure that the info got out that it's not as big of an issue as it used to be. Other manufacturers have different cutoff voltages for their receivers. I don't know what it is for Futaba, but I know that Airtronics 2.4 systems have a cutoff voltage of 1.8v before the receiver shuts down.

Hope this helps

ken
Well, Ken, we know this, but there are many on RCU that still think that this has not been resolved. Of course, it has been, but the best way to inform these folks is just to recommend a 6 volt pack. So, if they happen to latch on to a legacy receiver, then the problem becomes a non-problem.

Dick.

Gray Beard 05-10-2011 02:13 PM

RE: Rx Battery Placement.
 
Any idea if Horizon is still taking these RXs back and replacing them?? I was offered four of the old ones at a really good price not long ago. My 2.4 is Hitec though so I gave it a pass. I do still need a big bundle of Hitec RXs if I want to change over completely. I notice they never seem to come up on sale!![:o]

BarracudaHockey 05-10-2011 02:15 PM

RE: Rx Battery Placement.
 
They can update the firmware. Best to call and see if its covered or not.

CGRetired 05-10-2011 02:23 PM

RE: Rx Battery Placement.
 
Well, send me all you can get. I'll just use 6 volt packs and fly the he!! out of 'em.

CGr.

Gray Beard 05-10-2011 05:20 PM

RE: Rx Battery Placement.
 

Quote:

ORIGINAL: CGRetired

Well, send me all you can get. I'll just use 6 volt packs and fly the he!! out of 'em.

CGr.
Next time I run across the fellow I will see if he still has them. He wanted $20.00 a piece.


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