[NSRCA-discussion] Main battery redundant lead for receiver

Tue Jan 24 14:40:27 AKST 2012

When I first started flying electric pattern…..mah per flight was noticeably lower than now, going from 40-60 per flight to 60-80 per flight…..flying whatever was the current P/F sequences.  I suspect the increase is due to higher average flight speeds (much more watts at the motor now) and more demanding maneuvers (snaps and KE).

Regards,

Dave

From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Keith Hoard
Sent: Tuesday, January 24, 2012 11:02 AM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Main battery redundant lead for receiver

Anthony,

   On a typical flight, I'm guessing the radio only uses around 100-150Mah of power, while the motor is using 4000Mah, so that's about 4% more draw on those two cells.  In practice, I haven't been able to see any difference in the radio cells when I hook them up to my charger at the end of a flight.  Sometimes cells #1 & #2 are the high cells after a flight, so I think the power draw of the radio is negligible to our motor packs.

The problem with two regulators plugged into the same 10S (or 5S) pack is that you are creating a dead short between the cells thru the ground wires (typically a straight wire thru the regulator).  

Say you plug Regulator #1 into cells #1&2, and Regulator #2 into cells #6&7.  The regulator's ground wires now have 5 cells of voltage potential (5 X 4.2V = 21Volts) between them since they are plugged into cells # 1 and #6.  When those two ground wires are then plugged into your receiver either thru a switch or direct connection the magic smoke will escape and your retailer will rejoice.

Also, if you have both of your regulators plugged into your motor pack and the packs eject like Goose in Top Gun, you've lost both of your redundant power sources.  However, if you use a tiny 2S LiPo that is physically separated and secured inside your plane, you have both electrical and physical redundancy.  

Hmmm, just thought of something . . . maybe we should tie down the receiver so the main regulator can't take the receiver out with it. . . so many contingencies, so little weight . . .

Keith Hoard
Collierville, TN
khoard at gmail.com

On Tue, Jan 24, 2012 at 8:15 AM, Anthony Romano <anthonyr105 at hotmail.com> wrote:

Seems like a great idea but I have two questions. Do the packs come down out of balance since two cells are serving extra load? Is there a problem with parallel operation of two regulators?

Thanks,

Anthony

  _____  

From: joddino at socal.rr.com
Date: Mon, 23 Jan 2012 15:25:00 -0800
To: nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] Main battery redundant lead for receiver

I've been using this setup for sometime and it is working great.  I have my two cell LiPo charged to 7.5 volts and it is connected to a 6.0 volt regulator into the receiver.  The cable connected to the balance connector on the "bottom" 5S is connected to a 6.3 volt regulator so it supplies all the current to the system and the 2S pack never needs charging.  I'm using an 800 mAh pack but it could be even smaller.   

Jim O

On Jan 23, 2012, at 2:09 PM, Scott McHarg wrote:

Guys,
   Chris Moon just e-mailed me about some leads that were done at the factory.  These leads run off your balance leads to a voltage regulator and allow your main battery pack to be utilized as a redundant receiver battery.  It is NOT meant to be a primary but it will save 20+ grams if you're running 2 rx batteries.  You still have to run the 2nd regulator for true redundancy but you eliminate the 2nd battery.  These leads are factory made and eliminate the need to make them yourself with the concern about plugging in to the wrong cell.  I know in my article, I was pretty much against doing this as a backup but, with Chris having this made at the factory, he has all but eliminated making a mistake by tying to the wrong cell.  I have the link that I'll e-mail you off-list or you can just go to his website.  I don't want to break the NSRCA list rules by advertising for him even though he advertises with the NSRCA.  The leads are only $3.99 each and are found under the Connectors/Adapters listing.

Thank,
Scott

-- 
Scott A. McHarg

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