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BrianG · 02.26.2012, 12:59 PM

A little late posting to this thread, but FWIW, I've done a little experimenting with paralleling switching BECs (using the common LM2596 chip).

What seems to happen is that one invariably has a tad bit higher output voltage, so that is the one that handles most of the load. If the voltage sags a little, the other BEC starts to "help". When that happens, the current provided by each seems to "see-saw" so it appears they are sort of fighting each other (not really fighting - more like flip-flopping). The output current is higher than what each would be able to provide individually, but it's not exactly cumulative. And efficiency is not as high either.

I've tried adding a diode to the output of each to help isolate each BEC circuit, and it does help the see-sawing (but the higher V one does handle most of the load at first), but then you get the extra ~0.7v voltage drop, so whatever gains in efficiency are achieved by the isolation are negated by the losses of the extra diodes.

So, in the end, it is better to simply use a single BEC that has the current output required rather than try to shoehorn two lesser BECs.

However, DimensionEngineering BECs can be paralleled. I'm sure BEC design has a lot to do with whether they can be effectively paralleled or not, so YMMV.

	(#5)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	02.26.2012, 12:59 PM A little late posting to this thread, but FWIW, I've done a little experimenting with paralleling switching BECs (using the common LM2596 chip). What seems to happen is that one invariably has a tad bit higher output voltage, so that is the one that handles most of the load. If the voltage sags a little, the other BEC starts to "help". When that happens, the current provided by each seems to "see-saw" so it appears they are sort of fighting each other (not really fighting - more like flip-flopping). The output current is higher than what each would be able to provide individually, but it's not exactly cumulative. And efficiency is not as high either. I've tried adding a diode to the output of each to help isolate each BEC circuit, and it does help the see-sawing (but the higher V one does handle most of the load at first), but then you get the extra ~0.7v voltage drop, so whatever gains in efficiency are achieved by the isolation are negated by the losses of the extra diodes. So, in the end, it is better to simply use a single BEC that has the current output required rather than try to shoehorn two lesser BECs. However, DimensionEngineering BECs can be paralleled. I'm sure BEC design has a lot to do with whether they can be effectively paralleled or not, so YMMV.