BEC or 2s Lipo

[Highflyer028]

I know this is a common question and always a subject for argument BUT I was doing some research on the vstabi website and they say using the Western robotics 14s BEC is not safe. Are they saying the voltage drops are unsafe for the vbar or for the receiver. From what I understand futaba receivers have a more tolerable voltage drop range and Spektrum go into brown out very easy. Any one know what setup Kyle Dahl ran the year he competed with the 800?

[rcmarty]

If i recall correctly the WR bec was fine. A scope was needed to see the low voltages the vbar was commenting on.

They went on to comment it wasn't long enough to cause a vbar shutdown. If i'm correct the people involved were running futaba rx's.

But there is something going on in the background although it's not an issue yet ( IMO )

Myself i run a rx pack which was tested in the same situation and didn't suffer from a voltage dip (not matter how short).

WR are a good quallity bec with an even better track record.

But with the high voltage , crazy servo's coming out these days, all that power comes at a price. Amp draw , back EMF , etc.


If i recall correclty kyle competed all last year with WR bec with 0 issues. So this is a proven setup.

Myself i'm sticking with the 2s lipo and trying to get a better understanding of how a lipo cell reacts once failed. I'm leaning towards the 2s2p rx packs in case one cell were to fail it the other in parallel would cover me unitll i recharge again.

martin

[Highflyer028]

I have used the same western robotics 14s BEC on my goblin for a year now with zero issues but this heli is quit a bit heavier and am just a little concerned. As long as the vbar/receiver doesn't reset or quit on me because of a very quick drop in voltage then I can feel comfortable. As always I know there is a chance of the actual BEC failing but at some point I need to just fly it and not worry about everything. A 2s lipo battery could fail although its probably less likely but then again a servo could fail. Always a chance in this hobby. Thanks for your input. I'm leaning towards using the WR BEC and keeping it nice and clean setup.

[dahld]

Q; "Any one know what setup Kyle Dahl ran the year he competed with the 800?"

"rcmarty" is correct. Kyle ran on all three of his 800 XXtremes the year he competed with the machines (2011), the WR Super 14S BEC, wired for 14S input. No issues.

(-: Dave

[rcmarty]

That's what i end up saying also.

I explain my thoughts and theorys on both sides.

Then i go on to say you need to pick a plan and go with it. If something fails your coming down. Anything can fail.

I also throw in that there are no promises one you take off. Part of the adventure


I think a WR bec would be ok , and i'd feel somewhat comfortable with using one also. My 800 cost alot more than my typical heli and made me think alot harder about electronics. I even have a WR bec here on the bench, but i decided to go the lipo route for my 700 and 800.

That being said , there is some dipping going on so we are putting the BEC to work. Not an issue at this time, but with the evolution of powerfull servo's it's something to keep a close eye on. The next servo just might put it over the top. ( I suspect were close at this time _ IMO )

Martin

[rcmarty]

Well my memory isn't all that bad then .. lol

I opted out of using my 200+ flight 8717's at 8.4v to a set of 8917's.

Dave and kyle have had great success with them. I'll be happy to replace at ~ 1200 flights

Martin

[Highflyer028]

Thanks guys. I cant even begin to think how many times i decided to do one setup only to change my mind ten minutes later. I will install the WR tomorrow and maiden it this week!

On a side note. I used a 2s lipo today to complete my setup of the vbar. In the vbar software it would not show the current voltage. Any ideas what that's all about. I had the 2s plugged into the channel 4 port on the vbar. All my other heli's register current voltage and minimum.

[Sky_]

Hi,

I use a proven quality of a 2s LiPo power supply! Works perfekt!

[Streborz]

I'm almost done with a Logo 800 and I had the same questions, that's why I am here looking at this post.

After setting up a new heli I will run the collective up and down rapidly on the bench to see what happens. Well sometimes things happen on the bench that you would not like to see in the air. For instance. This current setup is a Logo 800 stock combo kit with Futaba BLS157HV cyclics, Savox SB2272MG tail, Silverline VBar 5.3 and Castle 20 Pro Bec. After about 15 collective inputs the system would shutdown and go to failsafe. Not good.

This had happened to me once before with a stock Align kit and 3GX and it ended up being the 3GX unit dying under the same test. The Align BEC was fine and has been flying for better than a year now with a Mini VBar 5.3 Blueline in it instead.

This looked like it was going to be the same problem again in this case. I thought maybe the VBar was crapping out. Surely 20amps is more than enough... Not having another lying around, I decided instead to take the Castle BEC out of the circuit and run the system straight 2s lipo, run the same collective test again and "BAM" no more shutdown.

What I took away from this experience is.
1. Less is more. The fewer components the better.
2. I bought this HV stuff so I could run the system on 2s and I'm going to stick with it.
3. 2s lipos do not stay at 8.4v for very long. They will most like run in the low 8v to high 7v for most of the flight.
4. And this is the most important to me. If it is going to fail it will likely be through over voltage to the servos or it is going to fail due to BEC brown outs.

Either way I lose, so the BEC has to go. I am not willing to buy 5 different BECs to find out which one is going to work out for me when so many already are having success with the straight 2s setup.

That's where I'm at on this topic.....for now.

[rcmarty]

A quality bec like the WR 14s unit should run those futaba bls's without issue as the bls are light on amp loads.

BUT there are voltage dips as seen by the vbar log (sometimes) , once you get the scope on it (thanks to mrmel) you can see the 8.4v dip to 2 something for a slight amount of time. The time is short and isn't causing an issue at this time with low draw servos like you bls's (for example).

As the servos get more an more powerfull the bec's are going to have to go.
For example there isn't a bec that will run the new hv align servos (750's i recall)

This trend will only continue ( IMO )

I think the next evolution in servo's is going to be a better connecting system. 20g wires on the little pin slider combo is only going to put up with so many amps. Physics can't be fixed.

I built up my logo 800 last year and went over this very topic for quite some time. I have a bought and paid for WR 14s bec on my bench modded up with nice silicone flexable wires. In the end i decided that i'm going to have to babysit another battery. I'm running a 2s2p 4000 pack so i have a huge safety margin to play with.

On another bec related topic ... is a 2s2p pack better than a 2s1p pack , not that there are many failures in a rx lipo in good visible and taken care of condition.


These are heli's after all , make your call and live with what ever comes your way. Is the way it is.

Martin

[Highflyer028]

I now have around 40 flights using the WR BEC with no issues. Looking over the vbar logs I don't see any low voltage warnings. Everything is working great. Love the heli.

[rcmarty]

Yup the WR becs are the good ones. Several reports of them working well with select servo's.

Some servo's like the new hv align's are too much for even the WR.

So , yes were doing good today , and with some due dilligence you will be safe.

Next generation of higher power servo's i forsee (IMO) better bec's or no bec's


Martin

[7hvman]

Good stuff and just in time for me to pick a path.

Question,
If I were to run 2s2p lipo with a mini v bar. Do I just run both lipo with a Y harness or do I want to split feed them in 2 places on the v bar if I can?


I thought when you added 2 battery and y them together on a y harness going from 2 battery to 1 port that the lowest battery will drag the higher one to that level? Or do I have it wrong? If I have a battery with 1 bad cell and the other pack is good and i y them together will the good pack over ride the bad battery and keep the power up to the level of the good battery?

Let me know thanks

[rcmarty]

2s2p refers to a single packs wired up as a 2 cell in parallel. So there isn't any issue with one set of cells being higher than the other as there connected all the time.

2 seperate batteries ( 2 x 2s1p ) would have the potential to have one low and one high if the weren't used as a team at all times.


In theory if one of the cells were to go out on a 2s2p pack , the other should carry the load (provided the bad cell still passes power). But chances are very slim as the light load of a radio system is nothing for today's modern lipo. Light load = longer life with less chance of failure.

Martin

[richardmills]

Originally Posted by rcmarty

For example there isn't a bec that will run the new hv align servos (750's i recall)

For what it's worth there are 2 goblin 700s at our field one with the savox 2271/2272 and one with the align hv equivalent both running off a Gryphon bec which has 15a peak and only 7a continuous. They have been flawless to date. One of them is flown very hard. Their both running the bec off a single 6s pack.

[One_eye]

Can someone advice if the Kosmic 200 internal BEC good enough for the Xxtreme 800 with Futaba BLS172HV and BLS256HV?

Is it advisable to have a lipo buffer pack? If yes, what is a good capacity? Will a TP 350mah receiver pack too small?

[One_eye]

Originally Posted by One_eye

Can someone advice if the Kosmic 200 internal BEC good enough for the Xxtreme 800 with Futaba BLS172HV and BLS256HV?

Is it advisable to have a lipo buffer pack? If yes, what is a good capacity? Will a TP 350mah receiver pack too small?

Anyone can advice?

[rcmarty]

While i can't say for sure. ( i opted for jr and lipo rx )

the futaba bls series are known to be lower on the amp draws , and the kontronics esc have one of the best bec's out there.

With what i've read you shoudl be good to go.

Please verify with someone with more knowledge or driect experience before going this route.

I'd hate to see a shiny new bird scratched up based on my assumptions

Martin