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Old Aug 20, 2014, 04:32 PM
aka Mr.Side-Winder
Jeff Winder's Avatar
United States, OH, Cincinnati
Joined Jun 2007
383 Posts
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Seperate RX batt or seperate BEC?

For a Full House ALES setup......Just wondering how many people out there are using a separate rx pack to power their receiver/servos and how many are using a bec, (separate from the esc).

I've got a build that is going to be tight on space, (really no room for an extra battery).....and I no longer trust the integrated bec's built into esc's as I've had brownout issues when pulling heavy amps.
Was thinking of using the
Castle Creations CC BEC 10A 6S Switching Regulator

The unit is rated for higher amps (by a factor of 3 from an integrated bec/esc), and is separate from the esc, but is this just going to put me back into the same brown out issues?
Anyone using one of these? Any known issues?

This CC unit would solve a lot of my problems for space AND voltage issues as it can be set to only output 5v.......I have some servos that want only 5v and the only rx pack I can fit and has enough amperage is a LiFe pack at 6.6v.
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Old Aug 20, 2014, 06:04 PM
A witty saying proves nothing.
kcaldwel's Avatar
Joined Jan 2007
3,569 Posts
Jeff,

There are no reliable statistics of failure rates of separate batteries (human error not keeping them charged, pack failure) vs. outboard BECs, so it is all opinion and anecdotal evidence. That is not really worth much.

I've been using several of the CC "10A" (check actual rating at your input voltage) with good success. I've never had brown-out issues on the many e-power airplanes that I fly with the ESC BEC either (FrSky).

Although there are some stories on the interweb about problems with the CC BEC, it looks pretty good in this testing:

http://www.rcgroups.com/forums/showp...5&postcount=44

http://www.rcgroups.com/forums/showthread.php?t=1277428

I did have an interesting experience with my big Osiris pattern airplane that I am running a CC BEC in the other day though. The motor suddenly cut-out during a downwind pass, about 7 minutes into a flight. I managed to dead-stick it to quite a good landing, and while I was walking over to it twiddling the controls, everything quit. It turned out one cell in the 5S pack had gone open circuit, so there was zero voltage at the terminals. The other 4 cells were still at about 3.8V.

That is the first time I've ever had a cell go open circuit, and an outboard BEC won't help with that situation. I'm still not sure it is any less reliable than a separate pack that I have to monitor and charge, and I don't usually have space in my sailplanes for another pack anyway. I'll continue to use a separate CC BEC for now.

Kevin
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Old Aug 20, 2014, 08:37 PM
Registered User
Joined Mar 2005
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850 LiFe powers the rx and 6 digital servo's in my plane. ( no regulator )
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Old Aug 20, 2014, 08:48 PM
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Leadchucker's Avatar
Joined Sep 2008
3,429 Posts
Quote:
Originally Posted by kcaldwel View Post
............... I've never had brown-out issues on the many e-power airplanes that I fly...........
I've never had anything close to a brown out in any of my sailplanes. Just thinking out loud, but if you're pulling that many amps to lower your battery voltage to brown out levels, it sounds more like insufficient battery capacity in maH's or C rating rather than BEC problems. If that is the case ,you'e going to have the same trouble with a external BEC. I also don't know how your radio is going to brownout voltage without the LVCO shutting down your motor.

For example: Default LVCO for a Castle ESC is 3.2 volts/cell so even with a 2S lipo you would still have 6.4 volts, a Hitec RX minimum voltage is 4.8, Futaba calls for 4.2, some other are 3.5 volts. You should still have plenty of voltage to not go into brownout. It's pretty much accepted practice to run 6 digital servos on a switching BEC, if you do have a switching BEC. Something don't add up.
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Old Aug 20, 2014, 10:51 PM
A witty saying proves nothing.
kcaldwel's Avatar
Joined Jan 2007
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Quote:
Originally Posted by Leadchucker View Post
I've never had anything close to a brown out in any of my sailplanes. Just thinking out loud, but if you're pulling that many amps to lower your battery voltage to brown out levels, it sounds more like insufficient battery capacity rather than BEC problems. If that is the case ,you'e going to have the same trouble with a external BEC. I also don't know how your radio is going to brownout voltage without the LVCO shutting down your motor.
I suppose if you are trying to draw near max current out of an internal BEC in an ESC, with the ESC also generating heat, the internal BEC might start to drop voltage if it gets too hot. Some of the internal BECs actually have pretty low continuous current ratings, and it is possible they might overheat and shut-down.

I've never had that happen, even on cheap ESC's internal BECs pushed pretty hard. I even had an ESC on fire once, and the internal BEC worked fine until I almost had it landed. There wasn't much left of the ESC at that point.

The voltage from the battery will only have to be 6V or so to drive the BEC, so you would have other problems long before the BEC would shut down from low battery voltage. The ESC should shut-off or throttle back the motor if the battery voltage gets too low, probably 9.6V on most for 3S.

What are the symptoms of your brown-outs, Jeff?

Kevin
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Old Aug 20, 2014, 11:10 PM
Mesa AZ, it's a dry heat!
USA, AZ, Mesa
Joined Oct 2004
605 Posts
A separate (CC) BEC is the way to go if space is tight. I have several in use right now.
The Castle Talon ESCs have a higher rated BEC than most, but the largest they make that is suitable for sailplane use is a 35A. I wish they would make a 55A or 60A with a 10A BEC.

Iain
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Old Aug 21, 2014, 06:09 AM
turn, turn, turn.
Athol, Massachusetts
Joined Oct 2005
10,260 Posts
I use a separate bec, if I have a feeling that my motor battery might explode because of pushing it too hard.
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Old Aug 21, 2014, 07:07 AM
You looking at me?
Ed Franz's Avatar
USA, KY, Burlington
Joined Sep 2001
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Quote:
Originally Posted by Ronald Mong View Post
850 LiFe powers the rx and 6 digital servo's in my plane. ( no regulator )
Same as I do.

Ed
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Old Aug 21, 2014, 09:53 AM
Flying = Falling (Slowly)
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Tulsa, OK
Joined May 2004
2,550 Posts
I've tried every possible combination and have finally defaulted to using a good ESC/SBEC combination for the virtues of simplicity. Some observations:

ESC WITH SEPARATE BEC.
Saved a plane once with this combination, but only by the grace of God. The ESC (a new Castle ICE) blew up -- and I mean exploded -- it scorched the wires to the BEC, but did not short them out. If you use one of these setups, arrange the components so a massive ESC failure will not damage the BEC OR THE WIRING TO IT.

LiFe's and 123's
Besides the added bulk, I gave up on these because they required me to keep track of how long I ran them. The discharge curve on these cells is so flat that battery meters do not accurately measure remaining pack capacity.

SCORPION BACKUP PACK
These are pretty slick -- they are small battery packs and associated electronics that allow the device to remain in an OFF position unless and until there is an interruption in the main power source. They work well, but you have to arm your plane and THEN arm the backup pack before flying and then remember to disarm both of them after you fly or the backup will run itself down. A tend to have memory lapses and discovered on several occasions that the backup pack was run down after I flew.

I finally gave up and decided to use a good ESC/SBEC that was very understressed -- 70 amp ESC for a 50 amp load and which I never ran at partial load (partial loads are harder on ESC's than full loads.) I use good batteries and never run them to less than about 50% of capacity. I mostly charge them at home with the charger attached to the computer and monitor individual cell characteristics and pack resistance. I pitch any pack which is not up to snuff. My ALES planes all use MKS 6100 servos which are small, light, strong and reliable. The total maximum draw for 6 servos is about 1 amp. The maximum stall current for any one servo is about 1 1/4 amps. Since Castle has gone to their EDGE ESC's I have been forced to change brands because the EDGE ESC's will not fit in my planes. I am now using a Jeti Advanced Pro 70. They have a very compact form and have been rock solid so far.

I do have one plane that uses a separate SBEC. I have a TopModel Fascination that I am using as a testbed for some GPS stuff and I am not certain what the maximum current might be for the system so I am using a Jeti Advance Pro 70 OPTO with a separate Jeti Regulator. The regulator is good for 6.2 amps steady and 12 amps peak. A very nice setup. And one of the features the Jeti stuff has is a ON/OFF switch which allows you to kill the system easily when you are not using it.

Happy Landings,

Don
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Old Aug 21, 2014, 11:48 PM
LSF303 / AMA Life Member
tkallev's Avatar
USA, IL, Wheeling
Joined Jan 2003
3,113 Posts
I run a separate pack ... the way the motor batteries are abused, they are the weakest link in the system, and a dead motor pack with a separate BEC is still a dead radio. Running 2100 mAH LiFe packs in full-house setups lets me fly the whole weekend ... and 850 mAH LiFe gives a full day. I do have backup backup batteries in case a LiFe pack gets used up ... but the LiFe's can be fast charged at the field with little abuse.

YMMV ...
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Old Aug 24, 2014, 05:31 PM
Registered User
United States, WA, Olympia
Joined Oct 2009
301 Posts
Edge Lite 75 in my Pulsar 3.6. No bec or rx pack required. BEC is rated 5A. I try to stick with simple. Minimal wires, connectors, components, extra batteries to charge, etc. My 2cents.
>T
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Old Yesterday, 05:48 PM
Skye Malcolm
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Upper Arlington, OH
Joined Mar 2009
629 Posts
1500 mAh NiMh 4 cell receiver pack with 6 digital servos (4 Airtronics 809s on rudder, ailerons, elevator and 2 Aitronics 761s on the flaps)

Skye
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