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Switchmode BEC vs. battery

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Old 01-15-2009, 11:11 AM
  #1
jjldk
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Default Switchmode BEC vs. battery

Is it too risky, or maybe even stupid, to use a Kool Flight Ultimate BEC (or others brands of 10S BEC's) instead of a battery in a 2K $ F3A plane ???
My radio is a JR9303 2.4GHZ with a Spektrum AR7000 in the plane.

Any experience good or bad ??


Jens
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Old 01-15-2009, 11:20 AM
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Chris Moon
 
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Default RE: Switchmode BEC vs. battery

Using a bec allows for a single point failure to not only lose power to the motor but crash the plane. All of the electric F3A guys that I know use a separate battery or even a dual receiver battery set up to power the radio. Not to say your idea won't work but I would want more redundancy.
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Old 01-15-2009, 12:45 PM
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Default RE: Switchmode BEC vs. battery

I run a UBEC from the 10S, and a second UBEC from a 730 mAh 2S. Both have diodes with different ratings I don't remember the exact value. The 730 pack is used only when the shorting plug isn't installed, and is a backup. With the shorting plug, power is drawn from the 10S. I have had one case where the 10S came loose and unplugged, and know of a few others, so didn't want that or UBEC failure to have any chance of causing a crash. The cost and weight of the redundant power brings a lot of added safety.

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Old 01-20-2009, 03:30 AM
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Default RE: Switchmode BEC vs. battery

Yeah, but what do you know Ken? LOL

Just kidding of course!!

What bec are you using and how much does it weigh? That seems like a good idea. One I hadn't though of.

I may be out to practice with you guys on Sunday if I get my stuff back from Airtronics and installed in the plane.. Hope to see ya there!

Chris
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Old 01-20-2009, 05:36 AM
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Default RE: Switchmode BEC vs. battery

Some pattern guys are flying with a 2S 450 mAh pack for the RX! I been using the new switching ESCs with the built in UBEC, no issues at all but for bigger set ups, I prefer to use a RX pack. Just in case ... just ...
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Old 01-22-2009, 04:14 PM
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Default RE: Switchmode BEC vs. battery

In the past I used UBEC's exclusively in my 10 cell e-helis, and every one failed in time, but always at startup, So I just learned to put connectors on them and carry a spare. Then one fine day, I had one fail in a 3 foot hover, the machine just rolled over and died. I have never gone back to a UBEC or anything in between my RX power and RX. I use 4 cell NiMH packs only.\

Just my $.02

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Old 01-22-2009, 08:34 PM
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Default RE: Switchmode BEC vs. battery

Good info Chris..

C
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Old 02-01-2009, 04:13 AM
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Default RE: Switchmode BEC vs. battery

So the conclusion must be: Use it, BUT only with a backup.

Thanks to all, who make their comments.

Best regards
Jens
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Old 02-01-2009, 04:57 AM
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Default RE: Switchmode BEC vs. battery

I have never seen the need for it honestly. The Bec is quite heavy IMO. I would never trust one on it's own.

I run one 2 cell lipo, and a Jaccio perfect switch. Lipo's are much better than the nicads or nimhs.. I haven't had one lipo fail yet as a rec pack. But I do change the lipo rec packs yearly in my planes.

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