Twin battery / ESC model, splitting the power feed from the ESC's

[Steve_Wright]

So building up my Bronco which has twin batteries feeding twin ECS's. As per the instructions the receiver and servos will be fed from the BEC from 1 ECS by removing the red lead from one of the ECS leads before it goes into the Y harnes.

 

 

 

However running 8 servos and 3 electrical retracts off one battery seems a bit wrong. Can I take the power feed from the disconnected ESC and use it to power just the electric retracts and some LED marker lights I have planned for the model? If so is it a case of using the power feed from the ESC to the retracts (disconnecting the power feed going into the receiver) or do I need to do something with the negative lead too?

 

[Dale Bradly]

Can I take the power feed from the disconnected ESC and use it to power just the electric retracts and some LED marker lights I have planned for the model? - Yes.

If so is it a case of using the power feed from the ESC to the retracts (disconnecting the power feed going into the receiver)  -yes.

 or do I need to do something with the negative lead too? -yes/no/maybe... keep all the negatives joined together. i.e. the negatives from the 2x esc, to the rx, and out to the retracts. If you think about it, the negatives of the 2x esc and rx are already joined together at the y lead in your top drawing, the retracts need to share this common negative line somewhere.  

What i have done in the past, is made a custom lead, whereby the retract channel leaving the rx has the red wire peeled out, (so power is not drawn from here), and the red that was removed in your top drawing is spliced in: Or in other words, the signal and negative go from the rx to the retracts to provide the operate signal, and the positive and negative from the esc goes to the retracts to power them.

 

[Frank Skilbeck]

Just a thought, what radio are you using? another option would be to use twin receivers. Rx 1 would be connected to ESC1 and flight control servos and Rx 2 to ESC 2 and retracts and lights. You could even split some of the flight controls to provide some additional redundancy, similar to pre-powerbox solution large model requirements.

[Max Z]

1 hour ago, Dale Bradly said:

What i have done in the past, is made a custom lead, whereby the retract channel leaving the rx has the red wire peeled out, (so power is not drawn from here), and the red that was removed in your top drawing is spliced in: Or in other words, the signal and negative go from the rx to the retracts to provide the operate signal, and the positive and negative from the esc goes to the retracts to power them.

If you do it that way, the current drawn by the retracts is still passing through 2 Y-leads,the associated plugs and the Rx negative bus until it flows back into the esc.

Yes you do need to connect all negatives together, but I would run both the positive and negative to/from the retracts directly into the 'disconnected' esc, and from there connect that esc to the Rx with just the throttle signal and negative leads.

The retract signal lead can thus be a single wire from the Rx to the retracts.

Edited July 28, 2021 by Max Z

[Hangarqueen]

I usually combine multiple power sources using dual Schottky diodes, thus creating redundancy in power supply.  In models with one motor, I combine the BEC from the ESC with an external BEC powered from a separate 2S or 3S battery.

[Steve_Wright]

1 hour ago, Hangarqueen said:

I usually combine multiple power sources using dual Schottky diodes, thus creating redundancy in power supply.  In models with one motor, I combine the BEC from the ESC with an external BEC powered from a separate 2S or 3S battery.

Any more into on this? It would make sense also to have both ESC bec feeds going into the receiver, but there must be a reason why you disconnect 2 (school electronics are failling me)the feed in via a Y lead is in parallel  sso no increase in voltage (?)

[Allan Bennett]

40 minutes ago, Steve_Wright said:

Any more into on this? It would make sense also to have both ESC bec feeds going into the receiver, but there must be a reason why you disconnect 2 (school electronics are failling me)the feed in via a Y lead is in parallel  sso no increase in voltage (?)

 

Check out this thread.  This does not share the load between the two sources, but it allows one to take over if the other fails.

 

With retracts though, I always use a separate power supply in case they jam going up or down, and overload the supply.  If the BECs in your ESCs are adequate for the number of servos you've got, I would power the rectracts by taking the red wire and a duplicate black wire from the ESC that's not supplying the receiver.  The retracts would then need a black wire and signal wire (but no red wire) from the retracts channel in the receiver.

[Chris Walby]

The point of the diodes is to effectively isolate the two supplies from each other while still supporting the load. If you just Y lead the two supplies then any voltage difference will generated what could be a very destructive circulating current causes one or both supplies to fail.

 

IMHO there is a balance between complexity and resilience and I can see the point (as I was advised by a very knowledgeable UK supplier of batteries, motors, ESC's and UBEC's) just just install a 3S2200 lipo and 20A UBEC. Its a 80 inch ic model and has a canopy so just a case of plugging the lipo into the UBEC, fit canopy, fire up the engines and go fly. No switches to fail, no duel supplies to foul up or need testing, just if a servo packs up enough current from the UBEC to clear the fault without dropping the RX voltage.

 

If you have a couple of main batteries then feed the RX using both via the ESC's with blocking diodes, but bear in mind if a servo fails there might not be enough current to clear the fault without dropping the RX out. Or separate the RX and some servos from others (like retracts) so that one ESC feed one lot and the either ESC the other or separate RX battery and UBEC if weight is no an issue.

 

Lots of ways to skin the cat. 

[Hangarqueen2]

I'm sorry but I haven't been able to reply, because I can't seem to be able to login with my new account (Hangarqueen) on the forum.  I have reported it twice already, but have gotten no reply so far.
But meanwhile, others have replied for me, with the correct information.  I hope to give a decent reply soon, when my account is all set.