[NSRCA-discussion] HV Direct Drive

[Vogel, Peter]

Also known as a ground loop.  A better use of this approach of using the balance tap, iMHO, is for redundant power without a BEC.  So you can still use a small RX battery, you just parallel it via the switch harness to the bottom two cells of your main pack, but it DOES need to be the bottom two cells or you will instantly kill your RX and possibly your ESC.

Peter+

Peter Vogel| Distinguished Architect, SBSEG Online Ecosystem, Intuit | SOI: 5-2-4-1 | Admin: Lorinda Martinez<mailto:lorinda_martinez at intuit.com>


From: NSRCA-discussion <nsrca-discussion-bounces at lists.nsrca.org> on behalf of Duane Beck via NSRCA-discussion <nsrca-discussion at lists.nsrca.org>
Reply-To: Duane Beck <duane.e.beck at comcast.net>, General pattern discussion <nsrca-discussion at lists.nsrca.org>
Date: Tuesday, October 16, 2018 at 7:22 AM
To: "tjpritchett at aol.com" <tjpritchett at aol.com>, General pattern discussion <nsrca-discussion at lists.nsrca.org>
Subject: Re: [NSRCA-discussion] HV Direct Drive

If you tap the RX supply off the wrong 5S pack, or the wrong side of the correct tap, there will be a voltage potential between the RX ground and ESC ground, causing unrestricted current to flow across that ground loop. That will damage the ESC and possibly also the RX.

Duane

-------- Original message --------
From: tim pritchett via NSRCA-discussion <nsrca-discussion at lists.nsrca.org>
Date: 10/16/18 10:13 AM (GMT-05:00)
To: anthonyr105 at hotmail.com, nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] HV Direct Drive

Can you re-word the second sentence....I don't follow.

-----Original Message-----
From: Anthony Romano via NSRCA-discussion <nsrca-discussion at lists.nsrca.org>
To: Scott McHarg <scmcharg at gmail.com>; General pattern discussion <nsrca-discussion at lists.nsrca.org>
Sent: Tue, Oct 16, 2018 8:52 am
Subject: Re: [NSRCA-discussion] HV Direct Drive
You have to be very careful with this because you can create a floating ground. I used tap of one 5s and grabbed the wrong one frying the ESC.

________________________________
From: NSRCA-discussion <nsrca-discussion-bounces at lists.nsrca.org> on behalf of Scott McHarg via NSRCA-discussion <nsrca-discussion at lists.nsrca.org>
Sent: Tuesday, October 16, 2018 8:38 AM
To: Tim & Janet Pritchett; General pattern discussion
Subject: Re: [NSRCA-discussion] HV Direct Drive

There are quite a few folks that do this.  It works just fine and certainly eliminates weight.  John Gayer showed me this technique and actually gave me several adapters.  My only complaint is that this technique still gives you a single point of failure.  If something happens to your motor pack (as a whole) and it's rendered useless in flight, you've lost the ability to land your airplane.  I still run a 350 mah 2S pack for redundancy and then the primary is the 2 cells of the 5S pack.  All you have to do is set your voltage regulator on one to a lower voltage than the other.  This should result in your RX pulling the current from the higher voltage path and the other is simply a backup in case of failure.  This is the lightest way to have redundancy.


Scott A. McHarg

Takeoff is optional.  Landing is mandatory!


On Tue, Oct 16, 2018 at 7:21 AM tim pritchett via NSRCA-discussion <nsrca-discussion at lists.nsrca.org<mailto:nsrca-discussion at lists.nsrca.org>> wrote:
A friend of mine suggested that with high voltage equipment, a dedicated battery is not needed for the receiver and servo's.  Plugging in the balance leads from the 5s power packs directly into the on/off switch to the receiver provides the same voltage.  This is true; the red/blue wires (on my packs...) in the balance leads produce 8.4v.  A simple 5s plug and a two wire harness could be easily made to supply power to the controls, and could even be 'doubled up' to supply power from both 5s packs.  My flight pack usually only drains ~30mah per flight, so that equates to ~7mah per cell in the power pack per flight - almost unnoticeable.

So the question; is anybody doing this with success, and is it recommended?  It eliminates some complexity maintenance and weight, so it seems worth asking. The math seems to work...
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