bovick

Hi,
I was wondering if anyone could confirm for me if using 2 phoenix 25 escs both with the bec enabled hooked into the reciever should be ok... From what I understand: everything is being powered off the same battery, and the voltage on the combined BECs should be the same.. with only the added benefit of having additional amps avail for servos. Correct or no? Has anyone successfully done this? Anything to watch out for?
thanks

Walt Thyng

My Feedback: (9)

You need to disconnect one BEC by removing the red wire from the servo plug and insulating it. Leaving both in will result in waaaaay to much amperage for the servos AND the receiver (remember BOTH are powered from the BEC).
Walt

pilotpete2

Walt, IF the ESCs will allow both to be running in parallel, then by all means do it, there is no such thing as waaay too much amperage, only the device that is drawing the current can draw too much, the two BEC circuits in paralell will still result in only 5V being applied to the receiver/servos, so they will draw the same current, the only difference is that each BEC circuit will have half the current draw, this is definitly a good thing as it increases the number of servos that can be used.
Pete

bovick

Guys,
thanks for the replies... along with posting my question here, I did quite a bit of reading and research. What I've found may be of interest to you or someone so I'll post here. As it turns out, the BECs in typical ESCs use simple linear voltage regulation. And since there are bound to minor differences in the two supplies, hooking them up in parallel has the possibility of leading to them "fighting" each other. This will eventually if not immeidately result in damage to one or both ESCs, BEC, or the items being powered (servo,Rx,gyro,...). So although it is theoritically fine, the practical implementation is not ideal. On the flip side, I have run into a couple of people who claim to be running 2 CC phoenix escs in parallel powering over 4 servos without a problem... but it seems that situation might not last too long or perhaps is just special cases. If anyone who really really knows their stuff in the electrical domain could post a correction or real world trial.. It would be greatly appreicated. (I'm too cheap to risk my electronics for testing purposes )

thanks

R101

No expert, but tried 2 ESCs with BEC in parallel and the result was trouble with one ESC not working.

Removed one BEC from one ESC and everything was fine.

pilotpete2

Hey Guys,
You can only do it if the ESCs are designed to operate with two BECs in parallel, I believe CC does just that, always check the documentation, as to the two CC phoenix 25's that you have, check with Joe Ford at CC support, he will set you straight
Pete

bovick

good call! Joe would be excellent resource for the info.
thanks

damroadhog

Hi,

Dump the BEC on the pair NO BEC , let the Lipo's run your ESC's for motors only, use a battery for the RX and servos alone , this eliminates any RF noise and ESC cut out, Many have tried to use one ESC and every other combo you can think of for a twin set up, This way works without fail. Two ESC's with no BEC at all.

On a twin set up make shure you set the ESC's the same, for soft start , soft cut off and no brake.

Dave

pilotpete2

Dave,
Dead thread
In his case he was well advised to run both BECs in parallel, no problem with the ones he's using[8D]
Pete

damroadhog

Dead or not it's up and running , for all to use as a tool for learning




Still up for newbees to read, after all I found it.

Castel Creations advises NOT to run two BEC's in parallel, In fact only one should be used if any.

It is fine and correct to run two ESC in parallel, using an isolated battery for your servos and RX gives you the correct voltage and Eliminates concern about how many servos or of what type you can use and leaves the lipo power for the two motors.

Running twin motors requires some power, I dought you can provide this with only a 3s pack, any lager this CC25 must diconect the BEC and have isolated RX and servo power. Excess power to the BEC can cuase it to over heat and shut down, this is why on any twin drawing twice the amps, needing twice the battery you should eliminate the BEC.

What do you think ?

Dave

pilotpete2

Hi Dave,

CC makes no mention in their documentation about running 2 BECs in parallel, but I asked them a while back and was told their BECs would not back feed and will work fine, but that you do not double the current capacity, more like about a 50% increase. It seems that many use them in parallel with good results.
In sizing a battery for a single or dual motor system you must have adequate capacity so that WOT does not result in excess voltage drop. The current demands of a receiver and a couple of small servos added to the load on the battery is insignificant, if it's a problem then you did not size the battery to handle the motor/s either.
I started flying electric powered sailplanes back in the 80's when most ESCs did not have becs, in fact Joe Utasi of Jomar, one of the better ESC designers would not add them, even in the early 90's, but times have changed and the old issues of running the pack dead and crashing are not as relevant today, particularly with lipos. assuming you set an appropriate LVC.
Today, I feel you can make the case that using a BEC can be more reliable than a separate battery pack, a good case would be my 2M thermal ship, it's powered with a 2000mah 3S lipo WOT draws about 22A, about 240 watts which translates to about 150W/lb.[8D] motor runs rarely exceed 15 sec. so that many climbs are possible without drawing down the battery too low, in fact I limit my motor run to about 3 min. total, after that I will not make another climb, but feel free to thermal as long as my eyes and neck can stand it. Just the other day I had a flight that lasted almost 2 hours, with total motor time of 3:09, upon landing the pack was found to be at 30% capacity or roughly 600mah remaining, a lot of juice for a 4 channel PPM receiver and two hs-81's.
One has to use good judgment in using BECs, they certainly aren't suitable for all uses, I sure wouldn't use one in a high powered electric 3D ship, though I would probably go with a external BEC rather than a battery for that situation.
BTW, all my ESC's are CC, my most recent project was a bipe with 4 hs-55's and 3S lipo, I went as far as to call Joe Ford at CC to get his opinion on the setup, he assured me it would be fine, and it is, no issues whatsoever, but then I tend to use ESC's that are rated at twice the max current I"m pulling, so they tend to run cool. I think many of the problems guys have tend to be due to running ESCs up to the ragged edge of their ratings, then throw in the fact that they are running a "mystery" brand ESC , well it's no mystery why the smoke got out
Regards,
Pete

damroadhog

Hey Pete



Sounds like your on the wright track , I to use CC ESC and only CC, I use a CC45 to run my 480/1020kv

it just makes sence to me for the added safety to use a higher rated ESC than needed.

Flying and building most all Electric now, 40 and 60 size warbirds and 120 size Edge 540. I use all E-flite motors, just found them to be the most durable , 480,10,25,46,60,110 use them all.

I was on the phone with Castle Creations when building my C 160 twin with BL 25 motors and two CC45's, we went over the BEC issue for some time and conluded it would be the best idea not to run any BEC's at all due to the battery size needed for good strong filght performance on an 8.5 lb twin.

I have no issues with this set up at all , works like a clock. As a geneal rule for Me I always disconect the BEC when using a high power set up.

I do fly an Ripmax Spitfire with a BL 10 motor/CC 45 with three MN48 JR servos though the BEC with a Common Sense 3 cell 15c 11.1 v 2100 mah battery with PCM RX, grate set up and works like dream, but that's the limit for me, bigger or more power , out goes the BEC. good as CC stuff is I do not want to risk thermal shut down and lose the RX even for a split second.

The real deal here, most builders buy and use cheaper ESC's and do not go for the added protection with a lager than needed ESC, but use what they can just get buy with, for that reason alone, it's wise to give the advice to not use the BEC , I know you are like me and read all the post in here, how many times have you seen grown men fighting there set up , trying to run 5 servos off a 1.5 rated BEC, two motors off one ESC, you know what IM saying.

I allways say you get what you pay for BUT no matter how good your stuff is if you dont use it properly you will in most cases be sorry

Take care nice talking with you


Dave

pilotpete2

Hey Dave,
Likewise to you
Sounds like we're on the same track.[8D]
I don't do the large electrics due to the cost of doing it right, but I sure like the lack of vibration and lack of slime, in time I probably will try a larger electric setup, as many new ARFs in the .40-.55 size are now being built for E-power or glow, in fact I'm considering the new GP Revolver (available later this month) though I want to see positive feedback before I blow the gift certificates I have for Tower.
Regards,
Pete

bovick

Since my last post and some more education on the matter... haven't had much trouble running two ESCs nor dual brushless motors off one ESC (this was with the motors of same spec with rotors aligned and mechanically grouped -- works fine, but not very efficient). One thing I'll have to disagree on with my recent experience with quite a few non-CC escs and various BL motors is that for a LOT of applications, the cheaper escs and motors works JUST FINE and quite reliably so. I definitely agree with buying an ESC that does at least 25% over the max expected load... but unless you need programmability for some very particular area of control on an ESC (levels of soft start, brakes, etc)... a lot of decent and very reliable escs exist that do just as good of a job. I personally have several CC escs... but for much of my foam/park/and even 3D stuff that I've acquired... there is absolutely little difference in performance (other than maybe some small bit of efficiency). Namely I'm using several H-Wing Guard escs... which were a fraction of the cost of a CC. As for brushless motors, I've got an e-converted LST that I ran with both a very expensive Lehner Basic 3100 XL... and now switched over to a Feigao 540L 8T. The feigao is certianly heavier. It is certainly just slightly behind in efficiency. But at less than 1/3 the cost.. it is just as if not more powerful than the lehner motor. With airplane stuff, I've got a wide variety of BL motors and with a bit of research have often had very good performance.
The reason I this is up is that there are likely many newbies reading the forums, as I once did and still do... and many in the hobby have a similar mindset of wanting to get the absolute best performance and features... even if means having little to spend on more toys or extra parts... or ending up dropping out of the hobby due to financial problems. If someone is going to be building a large heavy model, going for competition, or otherwise going to be pushing the envelope with performance.. then by all means there needs to be stress on electronics with all the bells and whistles and programmability. However, for a lot of people I've run into, they seem to put a high premium on things like e-flite BL motors (which I'm not knocking... they're great)... simply because they've heard so much and just want to go with whatever everyone buzzes about as being the best. However, competition is good.. and a lot of stuff like LIPOs and motors can come for quite cheap with just small cuts in quality/specs (50,000rpm bearings instead of 65,000 rated as in the lehner/feigao example)... but from someone who isn't going to push the part to its extremes.. the high price premium probably isn't worthwhile.
Lipos are a great example btw... I now have several hexTroniks from unitedhobbies that actually put out much more violent power than several other higher priced ones I had. They are actually on par with Thunderpower in amps, but definitely heavier. Time will tell about longevity though ..but for the price, I could just replace them a couple of times and still come up even with the cost of the TPs

sorry if that was a little rantish... but I've seen people get into and then out of the hobby due to the expense --having always being recommended by others to buy such and such brands when in reality.. they really didn't need or understand the extra features.

pilotpete2

Rantish?, nah more like making some good points[8D]
One thing I didn't make clear in my next to last post regarding having all CC ESCs is that all but one (Phoenix 45) are T-bird series, no way you need a Phoenix on a Slow Stick, granted they are still more than the cheapies, but are a good value.
As far as lipo costs go, my first pack, a 3S 2000mah Kokam/Cellpro was 75 bucks, to replace it today with one of there new Revolution packs a 3S 2100mah is down to 48 bucks, good progress.
Gota go, wife just called me up from my dungeon.
Cheers,
Pete

skubacb

Actually, connecting the two ESC's in parallel is correct.

CC ESCs will not feed back to each other and you get twice the amperage of using a single ESC to power the RX and servos. You need to make some additional settings so as to not have one motor quit before the other. CC has a great article about this. See http://www.castlecreations.com/media/castle-scribe.html 3Mar06

-pkh-

My Feedback: (2)

Here's the excerpt from that article addressing parallel CC ESC BECs:

paul daniel

Hi Guys: I read about the two ESC's and have yet another question. I have GWS A-10 with the 55 fans and have two E-flight 400 brushless motors. I am using two 40 amp ESC's that I got from Hobby King and a 2000 mAh battery. I have disabled the red wire on one of the ESC's. What happens is that the motors run up to about 3/4 throttle and the left one starts to slow down on me. I'm good on amps and have checked it with an amp meter. I have tried switching disabling the other ESC and that doesn't seem to make things better. I have run both fan units separate and they are fine. Suggestions?
Paul

R101

How about disabling both ESCs (remove both red wires from the plugs) then try them with a seperate receiver battery?

paul daniel

I could give that a shot but adding weight on a plane of this size is not a good thing. Thanks for the suggestion as I think I have a couple of smaller batteries layinga around.
Paul

cyclops2

Think about your symptom Paul.
Run fine alone. Problem when together in the tight space of the plane.

Difference should be in the wires and their solid connections. DIFFICULT in the A-10.

BETTER to have 3" longer than needed wires so you can wire it perfectly & then fold the wires up neatly & STUFF them into the plane.

I have 2 Hogs. 5800 Kv motors & fans & a vertical launch prop job.

Rich

paul daniel

Hey guys: So after all the advice, thank you, I went back downstairs tonight to do some serious wrenching on the A-10. But before I start taking out the ESC's or switching motors, I try one last thing, swapping out the battery. I had a Common Sense 2000 mAh and plugged in a Thunder Tiger 2300 mAh. BINGO, it was the battery I'm good now and if the winds are favorable tomorrow, I'm going to chuck it.
Paul

Matt Kirsch

My Feedback: (21)

How'd it go?

I've seen that one-motor phenomenon before. The only thing I can theorize on is that it boils down to the "no two ESCs are exactly the same" concept discussed earlier in this thread. One ESC will detect the low voltage just a nanosecond before the other, and will slow down its motor. The reduced load from the slowed-down motor lets the battery voltage go back up, and the other motor never detects the low voltage, and keeps running at full throttle.

paul daniel

Matt: That was pretty much the deal. I flew a couple of other planes yesterday and then the winds picked up but since I didn't have anybody to hand launch the A-10 decided to pass. It will fly. At full throttle, the thrust coming out the back should push this bad boy around. A nice day here in Wisconsin would be light winds and 30's.
Paul

Wubbo

Not true, the current that is used is defined by the load and not the other way arround.
In my house i have a 16Amp fuse (at 230V that would be 3680W), but my 10Watt lamp does not blow because the current is defined by the load.