outside power supply to receiver

[Tim Callahan]

i have recently gone to a redundant receiver setup in my molded carbon fiber F5J gliders. thanks to Konrad & help from Wayne i was able to get a system working. Now i am being questioned as to why i dont have a seperate outside power supply to my receiver. so i got a couple seperate bateries from ALOFT they are 2 cell 900 as there is no paperwork with them i am assuming they are Life not Lipo. along with this i have been told that i will need to disconnect the RED wire coming from the ESC to the receiver when using a additional power supply that can connect directly to my main reciver. my question is that by doing this i am not really gettint a redundant power supply rather just a different one that does not run through the ESC ?? is that corerect ? if so where are the advantages ? at first i hade them both powered up to the receiver and things seemed to work fine but i have no idea weather the power was comming the main battery & ESC or it was comming from the 900 ?
Konrad are you out there?

 

[PressAllTheKnobs]

I should say I have no experience with F5Js so there maybe considerations I am not aware of but...

No you are not getting a redundant power supply. You are just powering your RX directly from its own battery rather than using the ESC as a BEC (battery elimination circuit) via the red wire. You must remove the red wire because otherwise the RX battery and BEC will "fight". Damage or strange behavior may result.

Unless you are fixing a problem... eg the BEC in your ESC is underrated for the servos you are using...you are probably just reducing overall reliability by adding a second battery.

Powering the RX from a secondary battery may make some sense in a motor glider because it would allow you to use a smaller capacity main battery...just enough to get you to altitude... and not have to worry that there won't be enough in the battery to power the RX and servos.

Another reason for doing it is that the BEC in ESCs can fail particularly if they are underrated to start with or if you get a servo binding up and drawing excessive power. A separate RX/servo battery, assuming it is healthy and charged can be more robust.

However you are replacing an automated system (the RX voltage from a BEC is built in) with a manual one (you have to charge and connect a second battery for the RX voltage) and the automated one is probably more reliable in practice. Given a well designed starting setup, a separate RX battery is probably more of a pain than it's worth and you are better off making sure you have a sufficiently rated good quality BEC.

If you want a redundant power supply you have to use something like the Standalone RBUS which has redundant power switch over mechanism...but that is probably not called for with something like an F5J.

 

[Tim Callahan]

Well thanks for a well informed response. i am a long time flyer (35 yr ) but fairly new to all the new and rapidly developing electronic 'stuff' that is becomming available to this market. i am using a FrSky TX plus and it does reconize the outside power supply so i do have a warning device on low power along with a visual. so once again thanks for your help on this issue.
Tim