Batterie Parellelschaltung, Fragen meines Freundes aus den USA, wer kennt sich da aus

Hello Steffen,
A warning came with my Castle ESC which says not to connect another power supply in parallel with the built-in BEC. In other words do not connect a 4 cell RX pack in parallel with the BEC.

The Castle ESC's have switching BEC's just like the three ACT BEC's that I got from you. I have always used 4 cell RX packs in parallel with my ACT BEC's and had no problem at all.

Other makers of some other switching BEC's warn against using a 4 cell RX pack in parallel with their products.

An exception is Kontronik, who RECOMMEND using a 4 cell RX pack in parallel with the BEC on their ESC's.

http://www.kontronik.com/images/stories/dmdocuments/anleitung_jive_2009_10_14.pdf (see p15)

Can you please find out if this is because the Kontronik BEC's are special in some way?
What could happen if I use a 4 cell RX pack in parallel with the BEC on my Castle ESC?
Does anyone else say it is ok to use a 4 cell RX pack in parallel with their BEC's?
 

Julez

User
Hi!

I have also put 4-cell packs in parallel with various BECs, and never encountered a problem.
However, if you want to be on the safe side, put a diode in the positive wire between ESC and RX. This will lower the voltage a little and prevent any interference between the battery and the BEC in so far that potential BEC or ESC damage will be prevented.
Your RC system will now be powerd by the 4-cell pack, and should it fail, the BEC will work as a backup.

Cheers,

Julian
 
Thanks Julian

Thanks Julian

here is his answer:
So it is a problem in theory only and no one has actually seen it occur? How does Kontronik do it? Do they have a built in diode in their BEC's?
Regards,
Jimmy

Kannst Du dazu noch was sagen?
 

Julez

User
Hi!

I can only speak for me, as I had no problems with TMM and Turnigy ESCs. I do not know what the difference between the respective ESCs from manufactures who advise against RX packs, and those who don't, is.
Maybe it is a theoretical problem only, but I cannot guaratee it, as I have not yet looked too deeply into how linear and switching BECs work exactly.

But if you put a diode into the one cable as mentioned before, you are on the safe side. Guaranteed.
 
Hi Julian,
Danke! Hier ist die Antwort, ich kenne mich da leider zu wenig aus...

I believe that the output of the BEC is essentially a bridge rectifier which is an arrangement of diodes or one-way valves for current. http://en.wikipedia.org/wiki/Bridge_rectifier

IF a higher voltage is connected in parallel with the bridge rectifier then the diodes in the bridge rectifier appear as a direct short to the higher voltage, and that will heat up those diodes. Too much voltage could result in too much heat and cause a failure.

Connecting a diode as everyone is suggesting will prevent the parallel power supply from reaching the diodes in the bridge rectifier, thus preventing overheating.

I think the key is to have enough resistance (length of wire) between the parallel power supply and the BEC so that small differences in voltage will not overheat the bridge rectifier. Then no protection diode (an extra point of failure) is needed. At least that is my theory. Maybe an Electrical Engineer will have a better explanation.

regards Jimmy
 
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