trex 600L combo external BEC

[FiLazer88]

Hey guys, I just got my 600L combo and am excited to start the build. I was wondering though, do the trex 600 kits usually come with an external BEC to power the gpro and servos? I know it doesnt include the battery, but I figured since it included the main ESC it would also include the BEC, or does Align still assume we are gonna run electronics off the main battery? There's ambiguity in the manual, it doesnt list the external BEC as "optional equipment" as it shows in the maunual, but does not list it in the included hardware either.

If it isn't supposed to include one, does anyone have any good recommendations?

Thanks

[Gladius]

The Edge HV80 does NOT have an internal BEC, so you'll need to get one. People do run their electronics straight off a receiver pack, but I never have, so I'll let one of them comment on that.

I'm using a Castle BEC Pro on my 600, and haven't had any problems with it.

[IrvingWashington]

I use a 2s lipo without any bec. Its about 100mah drained for each flight, so you can figure out how big you need the lipo to be. I think its the most reliable setup you can have.

I considered to use a castle bec, but Im not sure how reliable is, there are people who have had serious issues with castle or even another becs.

[FiLazer88]

Originally Posted by IrvingWashington

I use a 2s lipo without any bec. Its about 100mah drained for each flight, so you can figure out how big you need the lipo to be. I think its the most reliable setup you can have.

I considered to use a castle bec, but Im not sure how reliable is, there are people who have had serious issues with castle or even another becs.

Apologize for the noob question, but what do you run the 2s lipo into so it can power the servos and fbl unit? This is my first go at larger heli setups, and I can't find much out there to detail the setup.

[Gladius]

You just need some kind of adaptor, with whatever connector you're using on your rx battery on one end, and a servo connector on the other end. For a 600 size, you'd probably want it to have 2 servo connectors, due to current limitations of the servo connectors. Then, you just plug the servo connectors into your receiver.

Make sure the power leads go to the right slots in the servo connector. If you accidently connect the power lead to your signal bus, you'll fry the receiver.

[IrvingWashington]

Originally Posted by FiLazer88

Apologize for the noob question, but what do you run the 2s lipo into so it can power the servos and fbl unit? This is my first go at larger heli setups, and I can't find much out there to detail the setup.

No problem, yes with the 2s battery you power servos, receiver and fbl unit too, so you need HV servos with receiver and fbl unit supporting 7.4v too.

I built a wire with 2 servo wire extensions, xt60 in one side to the 2s lipo and two connectors on the other side to power receiver and fbl unit (not needed thought, just 1 connector needed here).

[pril250]

I still prefer using a regulated source with my electronics. To that end I power of a 2S pack 2000mAh or larger and a Western Robotics 10A linear BEC @6V for non HV servos.

[Smoggie]

Originally Posted by pril250

@6V for non HV servos.

He has HV servos, they are standard in the 600L.

Direct off a 2s LiPo is the cheapest and simplest way to do it. Only down side is the weight of the battery (only about 120g) and the hassle of charging it.
Alternatively use a good HV BEC powered off the main flight packs. This saves a few grams and you don't have to keep an extra battery charged, but downside is BECs can very occasionally fail.
It would be a 'strange' move to use a battery and a BEC with HV servos. It's kinda 'worst of both worlds' solution IMHO (weight and hassle of a battery, potential failure modes of a BEC).

[RC/DC_5000]

The 600L does not come with any means to power the servos and FBL. I recently built the 600L and think the separate RX 2s battery is the way to go. For a lot of reasons.

- RX pack allows a simple way to power the flight system for safe tuning and adjustments without the main motor powered up. This is a good feeling on a 50 volt helicopter with nearly 10 horsepower at peak.

- RX pack weight is nothing for the 600L. Negligible. If anything, its a positive factor- with 3300 batteries centered in their straps and the RX pack, the COG is perfect. The 600L is already carrying around 12s and a 700 class motor. Its a tank and makes its money from massive torque and lift.... not light weight. That'd be like Fat Albert ordering the triple cheeseburger and Diet Coke. The RX battery can not be felt versus a BEC in the air.

- RX pack can sustain continuous current of 40 amps+ whereas a BEC has around 10 amps continuous. When it comes to brownouts, I'll take the massive overhead. This should be the nail the coffin- At 48 volts the CC BEC Pro can only sustain 8 AMPS!! Thats scary because first, reduce that 8 amps even more... the 600L runs at 50.4 volts. Even MKS micro servos can draw up to 2 amps a piece. BEC? No thank you. Even wiring the BEC to one 6s pack only gets you about 12 amps continuous.

-Direct LIPO has no step down. Stepping down 22.2 or 44.4 volts into 8.4 volts is where the problems begin.

I considered the BEC too... but don't have a single regret about direct 2s LIPO. If you were to get a BEC, I'd wire it off the one 6s pack. The CC BEC Pro or the Hercules BEC's are pretty much the standard.

Another tip, I'd suggest you check your BL 8 series servos for a serial number on the bottom like B1511. Non serial number servos have major, major first batch failure problems. If they don't have serial numbers- I'd send them to Align USA for testing and very likely full replacement. I mean all four servos.

[Smoggie]

Yes, a 2s LiPo is fine but good quality HV BEC is fine too. Decent HV BECs are typically rated for 20A, which is enough to fly your ESC/FBL wiring, so no point having any more!

It's really down to personal preference. FWIW have an HV BEC on my Goblin and Trex 600 Pro and a 2s LiPo on my Dune and 7HV... All work great, no issues. BEC's work on exact same principal as your ESC, plus your FBL and Tx also have step down regulators in them... so dont be afraid of step down regulators, they are everywhere..

[RC/DC_5000]

Agreed. They both work. I guess the pros and cons will strike us all differently. I'll be honest, the biggest benefit I enjoy is just plugging in my little 2S pack to do all my setup and tuning.

And after having tons of brownout problems with BEC's from Align. Im probably scarred for life.

[ticedoff8]

I would look at the new Western Robotics line of Hercules "Super BEC"

http://www.western-robotics.com/herc...-BECG2_hp.html

They will take up to 14S input and the 3 cyclic servos and the TR servo are directly connected to the BEC (instead of the FBL)

[Luvmyhelis]

Originally Posted by Grumpy_Old_Man

He has HV servos, they are standard in the 600L.

Direct off a 2s LiPo is the cheapest and simplest way to do it. Only down side is the weight of the battery (only about 120g) and the hassle of charging it.
Alternatively use a good HV BEC powered off the main flight packs. This saves a few grams and you don't have to keep an extra battery charged, but downside is BECs can very occasionally fail.
It would be a 'strange' move to use a battery and a BEC with HV servos. It's kinda 'worst of both worlds' solution IMHO (weight and hassle of a battery, potential failure modes of a BEC).

Not necessarily so, I run small 3s lipos using a variety of high end bec's on all my larger helis. The bec issue comes from how hard it is to drop higher voltages down to the needed electronics level. So the less voltage is dropped, the easier it is on the internal bec components. This way, you end up using a small voltage 'step down' but have a much better voltage reserve. So, no more voltage dips under hard servo draw moves that we typically see in telemetry or logging using standard 2s lipos with higher end servos. And the bec's aren't being stressed.
The bec failures others such as Thomas, who owns MKS USA noted roughly three years ago in an interview that were plaguing the industry. Were all based off higher S rated main packs being regulated down. Not only through esc based bec's, which were the worst, but also main pack based bec's. He is now an aggressive supporter of external based electronics packs. Guys such as Scott Gray marketed the 3s based bec's seeing this same trend. I had a number of bec failures that cost me entire prototype helis early on. I wont discuss the brands as I don't want to get into that controversy storm. And then noticed servo bus voltage dips using a variety of high end 2s packs on numerous Skookum playback logs being sent my way.
Not to mention brown out issues with Spektrum rx's, especially in relationship to the Kontronik esc based bec's. I just had a good buddy who had serious issues with his on his Logo, which we solved by an external 3s pack using a Castle Pro bec. I have yet to see one of these lower end bec's fail doing it this way. Btw: he is selling off his $500 esc, as it was also a nightmare. His cheapo Yep 120 is working far better with zero issues....
So for many such as myself who are using high draw servos under extreme flying conditions. The use of good 3s packs using high end bec's made sense. Never had one fail now in thousands of flights.

I just wanted to paint the other side of the picture. But understand your comment.

[RC/DC_5000]

Stall Current (6.0V/7.4V/8.4V)
3800mA/4700mA/5200mA

This is the stall current for OMG H4 servos which are remarkably similar to Align's BL815 servo. http://www.omgrcusa.com/H4-Series-Hi...Servo_p_8.html

As you can see, when you stall these servos out, they can draw up to 5.2 amps a piece. Servos are getting more and more powerful and can demand a ton of current. The OMG servos are nowhere near the strongest... BK servos use much more current. Don't forget the FBL system and its high speed computer making extremely fast calculations and adjustments. Lets say you jammed the collective and got all three cyclic servos nearly stalled out. That's 15+ amps peaking right there. The tail servo will no doubt be getting worked trying to hold the tail.. The BEC Pro peaks at 20A and there's still more current needed to run the rest of the system.

So you're not only stepping down 22.2 volts... you are also potentially over taxing the circuit. I'll take my RX pack that can supply 66 Amps continuous current... versus the 12 Amps continuous of a BEC Pro.

[Smoggie]

Originally Posted by Luvmyhelis

Not necessarily so, I run small 3s lipos using a variety of high end bec's on all my larger helis.

But in the context of the OP's question, when running HV servos, why would you use a battery and a BEC?

What actual demonstrable advantage does having both the dedicated battery AND LV BEC have over simply using a 2s LiPo battery unregulated?

While the BEC might be very reliable it still is a potential failure point, and it adds a little weight and 'clutter', and it costs some money. There is no point having it if it brings no benefit.

It's a different story on standard 6V servos, granted.

[Smoggie]

Originally Posted by RC/DC_5000

I'll take my RX pack that can supply 66 Amps continuous current... versus the 12 Amps continuous of a BEC Pro.

A standard servo type plug as is used to connect power from the battery (or BEC) for feed to the FBL controller can only safely handle about 4-5A continuous, a little more in bursts. On large helis you use two of them but even when doubling up connectors it's a mute point about the BEC or batteries ability to supply current higher than about 12A continuous (or 20 in bursts) because the connectors would fail if you exposed them to more.

Anyway, if you are stalling out all three of your cyclics you have something seriously wrong with your setup!

I've nothing against using a battery, i do so on my Compass and Kasama, however a BEC can work fine too. Each has pros and cons, there is nothing fundamentally wrong with either approach.

[RC/DC_5000]

Wrong. The BEC as an entire unit has a peak supply of 12A continuous that it can step down and supply as a whole.

So... 3 cyclic servos= 5A per lead.... 15A taxed on the BEC. It's all coming from the one power source.. the BEC. Each lead feeds off the one supply.

If you nearly stall out your servos... you are using them... you obviously know nothing about how a servo works. They get close to being stalled all the time. Thats called stall torque. Thats how they hold the spinning disc with G forces. Thats how they hold your finger when you press down on them. It takes energy to resist moving.. how did you think they work?

Thats rhetorical. I asked that you leave me out of your trifling.

[Gladius]

How are you getting the power from your receiver battery to your servos? Do you have it wired directly to your servos, or does it run through your receiver or FBL?

[RC/DC_5000]

Take the BEC Pro for example. It has a 20A peak rating. It has two JR/Futaba servo leads that can each handle 5-8A continuous current. Agreed?

Those JR/Futaba leads can carry a lot more peak current than 5A continuous. That is why we have continuous and peak ratings. They are not the same. Continuous means it can handle it all day without overheating or damaging the component. Peak means that no more electrons will fit nor pass. When speaking of brownouts... we are only concerned with peak current ratings. Stressing your servos that far is a brief jerk or smack of the sticks. Then its over. So when you flog your 3D heli and for a tenth of a second, the flight system draws more than 20A at peak, you risk brownout with the CC BEC Pro.

It doesn't come down to a limitation of the wires. In the case of brownouts... the servo leads continuous rating of 5A (not official) does not mean anything. The JR/Futaba leads can handle a lot more than 5A current to satisfy the short peak draw from stalled servos. But the CC BEC Pro can not send any more current. Its peaked.

The difference- is the RX battery has current for days. The BEC has 20A at the very most for a very short time. I have two heavy duty JR leads from my RX battery to FBL to servos. If the flight system needs more than 20A for a split second at peak... those two leads can easily deliver it and the RX battery could add another flight system and still deliver it.

This may help distinguish the two power sources at their peak current. (Which is all that matters in a brownout)
CC BEC Pro Peak - 20A
Align 2S 2200 30C/40C burst - 88A

Use the stall current ratings from above to see how easy the 20A can get used up. Easily 5A per servo. No guarantees either way... but few drawbacks along the way. RX battery is light, powerful, and pretty convenient for safe setup.

[Gladius]

Where did you read that a JR servo wire can handle 8A continuous? I have only ever seen 5A continuous. The peak rating is actually the maximum rating that the wire can handle without damage, and only for a brief moment. It's not the theoretical maximum current that can flow. Trust me, I've seen the results of 4000V flowing thru the leads of a common volt-meter. It sent 3 co-workers to the hospital; 2 of them spent over 3 months there.

I've never seen a peak current rating for the JR servo wires. But I doubt that they can each handle 44A of current. That's all that Grumpy was trying to say - that the RX battery can't supply all that current to the receiver, due to the limitation of the wires.