700 Size Power: BEC or RX Pack?

[Smoggie]

Originally Posted by Steve_JR

Would you guys say the likelihood of a bec or main pack failure is higher than the bec being overloaded and frying the electronics?.

If the BEC is good quality and suitably rated the chance of either failure is slight. The way I look at it helis mechanically and electrically have scores of 'single points of failures' any one of which will end your day badly. I dont see that the BEC is inherently any less reliable than many of those other single point failures?.

[Ace Dude]

Originally Posted by Grumpy_Old_Man

If the BEC is good quality and suitably rated the chance of either failure is slight. The way I look at it helis mechanically and electrically have scores of 'single points of failures' any one of which will end your day badly. I dont see that the BEC is inherently any less reliable than many of those other single point failures?.

A well designed BEC is no easy task and there have been reports of quite a few failures on the forums over the years. Not only when they shut down from overheating, but when they fail passing the full voltage to all the on-board electronics (FBL, servos, etc.) causing a total wipe out. There are only a few BECs I would trust. YMMV.

[bredler]

Originally Posted by Ace Dude

A well designed BEC is no easy task and there have been reports of quite a few failures on the forums over the years. Not only when they shut down from overheating, but when they fail passing the full voltage to all the on-board electronics (FBL, servos, etc.) causing a total wipe out. There are only a few BECs I would trust. YMMV.

Care to elaborate?

[Ace Dude]

Originally Posted by bredler

Care to elaborate?

Kontronik (ESC+BEC), Western Robotics, R2 Prototyping, and Emcotec are, IMHO, the brands I have the most confidence in.

[exiged]

Hv set up on my 700 dominator- 1000mah lipo with back up guard.

[Smoggie]

Originally Posted by Ace Dude

Kontronik (ESC+BEC), Western Robotics, R2 Prototyping, and Emcotec are, IMHO, the brands I have the most confidence in.

Often people assume highest price must automatically mean highest reliability. The term we use at work is 'reassuringly expensive'

The only BEC I've had fail was a Gryphon Quasar 7075LMT (also my most expensive BEC!). But at least it failed in a safe way; one day i plugged the battery in and it simply didn't power up. A known issue apparently, something to do with inrush current on connection, it couldn't happen in normal operation, only on connection.

[Ace Dude]

Originally Posted by Grumpy_Old_Man

Often people assume highest price must automatically mean highest reliability. The term we use at work is 'reassuringly expensive'

The only BEC I've had fail was a Gryphon Quasar 7075LMT (also my most expensive BEC!). But at least it failed in a safe way; one day i plugged the battery in and it simply didn't power up. A known issue apparently, something to do with inrush current on connection, it couldn't happen in normal operation, only on connection.

Speaking from my own personal experience, I've never had a Kontronik fail me.

[Relisys190]

Originally Posted by exiged

Hv set up on my 700 dominator- 1000mah lipo with back up guard.

nice and light. How many flights can you get on it?

I usually limit to 3 flights on my 2200mah 2S. It yeilds 4.00 volts per cell after 3 flights. Safe and plenty of headroom for voltage sag.

I bring two 2200mah to the field and get 6 flights on the big bird.

[TheBum]

One reason I prefer using a BEC is I don't want to have to keep track of the charge on two batteries. Using a BEC is like getting a freshly charged receiver pack on every flight...assuming the flight pack was charged.

[LinusLarsson]

Originally Posted by Relisys190

nice and light. How many flights can you get on it?

I usually limit to 3 flights on my 2200mah 2S. It yeilds 4.00 volts per cell after 3 flights. Safe and plenty of headroom for voltage sag.

I bring two 2200mah to the field and get 6 flights on the big bird.

You are very conservative, 4.00v per cell is around 70% (or soo) left in the pack. I fly a smaller battery, 2S 1300mAh (75g) and they hold for a couple of flights with room to spare.

On my R5 I use a 850mAh battery and charge every flight.

[Relisys190]

Originally Posted by LinusLarsson

You are very conservative, 4.00v per cell is around 70% (or soo) left in the pack. I fly a smaller battery, 2S 1300mAh (75g) and they hold for a couple of flights with room to spare.

On my R5 I use a 850mAh battery and charge every flight.

Anal retentiveness sounds better than conservative.

LMAO

[Mercuriell]

I crashed once because of a UPS backup. I run most of my big electrics off a BEC - usually in a Kosmik or Jive. I usually have a switch in the line from BEC to flight electronics. I took my speed TDR up once with the Scorpion UPS backup,switched on from a previous flight - I had however forgotten to turn on the inline switch from the BEC - result enough power to spool up, take off, fly forward, then all control,lost as the tiny UPS lipo drained! Remarkably the heli powered down in a shallow dive and landed almost damage free in long grass!

[Ace Dude]

Originally Posted by Mercuriell

I crashed once because of a UPS backup. I run most of my big electrics off a BEC - usually in a Kosmik or Jive. I usually have a switch in the line from BEC to flight electronics. I took my speed TDR up once with the Scorpion UPS backup,switched on from a previous flight - I had however forgotten to turn on the inline switch from the BEC - result enough power to spool up, take off, fly forward, then all control,lost as the tiny UPS lipo drained! Remarkably the heli powered down in a shallow dive and landed almost damage free in long grass!

Why would you put a switch between the BEC output and the on-board electronics?

I have a switch between my buffer pack and on-board electronics, but never thought about putting one between the BEC and on-board electronics.

[JesusFreak]

Originally Posted by Thoemse

All align combos come with one. It is the Hobbywing 130A V4 ESC and there have been no negative reports about that one.
I would say that BEC is solid. I still went for the Ultraguard because it is cheap and very light. It wouldn't be needed most likely though.

I thought Aligh was bundling Castle ESCs with their packages now?

[JesusFreak]

How "safe" is it to use HV servos and just run a 2 Cell LIPO? I read someplace this was risky. On my 700 size Heli I use a ReactorX (which I'd love to find another of), with a 3 cell lipo.

I want to setup my new heli as simple as possible, but not risk failure. I have a 7200BX, which is not designed for high amp service, but my thought was I could run the power leads directly to the servos and bypass the receiver. I did something like this on my TREX 500, but it's been awhile. My biggest concern is that a simple 2 cell lipo may suffer a sag in voltage and do me in.

[CompleteDestruction]

Originally Posted by Grumpy_Old_Man

Why not power the BEC from the main flight battery?
That's why they are called 'Battery Eliminator Circuits'.. They are intended to eliminate the need for a separate Rx battery.

Otherwise just use an Rx pack with no BEC?

I find it really convenient to be able to power up the heli without the motor being armed. It's very similar to Flying Nitro.

My tail servo cannot handle a 2's pack.

[Atomic Skull]

Originally Posted by Thunder Fighter

On my 700's and bigger always use a 2s Lipo or LiFe with voltage telemetry and alarms. A 2s pack is a reliable solution and the telemetry means you can never take off without a charged pack. I feel adding backup guards to this increases the complexity with very little improvement in reliability.

//Dennis.

This works too:

[Ace Dude]

Originally Posted by CompleteDestruction

I find it really convenient to be able to power up the heli without the motor being armed. It's very similar to Flying Nitro.

My tail servo cannot handle a 2's pack.

I use a small 2s LiFe buffer pack (as recommended by KONTRONIK) with a Futaba HD switch harness between the pack and the on-board electronics. I can power up the on-board electronics w/o connecting the flight pack, just like a typical wet fuel setup.

[bredler]

Whoa there buddy. Your heli's gonna crash! That voltage indicator only costs like $3!!!

[Atomic Skull]

Originally Posted by Grumpy_Old_Man

but that includes the ESC to Rx wiring harness which you would have to add to the Rx pack. So to all intents and purposes you save the full weight of the Rx pack (116g in this case).

One thing I like about the 3DIGI, no wiring harness required just solder an XT60 onto the dedicated power leads and your good to go.