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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 12:41 AM   
Flyer88


 

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 3:59 AM   
Flyer88


 

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Status: offline 		How do you know if your two cell Lipo is staying balance if it just being fed by it main leads ??

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 4:23 AM   
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Status: offline 		Jim,
Are you going to make a Jaccio regulator/switch available that can be set to 8.20 volts and wiil take a 3s input? I like what you have come up with although my current setup with two regulators set to different voltages comes close to not ever needing to charge the backup.
I'm interested but not sure I'm ready to make a complete switch to HV servos.
John Gayer

quote:

ORIGINAL: OhD

Here is my plan for my next plane. All high voltage servos. Tap the low end 5S at the 3S pin on the balance connector and feed it to a Jaccio Perfect Switch Harness/regulator set to 8.2 volts. This is connected to the receiver. Connect a small 2S LiPo directly to the receiver through a conventional switch that allows current to flow in both directions. The system essentially runs off the motor power pack. This also keeps the small LiPo charged to 8.2 volts. The small LiPo, in addition to being a backup also serves as a large capacitor to keep the voltage constant. What do you think?

Jim O



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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 5:41 AM   
OhD


 

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quote:

ORIGINAL: Flyer88

How do you know if your two cell Lipo is staying balance if it just being fed by it main leads ??


The balance connector on the 2s LiPo is accessible and there are many devices that could be used to balance them, but I have never observed a 2s receiver pack being out of balance in about ten years of using them, and I very seldom used a charger with a balancer (maybe that's why I never detected an imbalance). But now that you mention it i will be checking more often.

Jim O

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 6:05 AM   
OhD


 

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quote:

ORIGINAL: jgg215

Jim,
Are you going to make a Jaccio regulator/switch available that can be set to 8.20 volts and wiil take a 3s input? I like what you have come up with although my current setup with two regulators set to different voltages comes close to not ever needing to charge the backup.
I'm interested but not sure I'm ready to make a complete switch to HV servos.
John Gayer

quote:

ORIGINAL: OhD

Here is my plan for my next plane. All high voltage servos. Tap the low end 5S at the 3S pin on the balance connector and feed it to a Jaccio Perfect Switch Harness/regulator set to 8.2 volts. This is connected to the receiver. Connect a small 2S LiPo directly to the receiver through a conventional switch that allows current to flow in both directions. The system essentially runs off the motor power pack. This also keeps the small LiPo charged to 8.2 volts. The small LiPo, in addition to being a backup also serves as a large capacitor to keep the voltage constant. What do you think?

Jim O




Hi John,

I did modify a linear regulator to provide 8.2 volts but the right way to do it is to use a switching regulator with a 10s input so you don't need to connect anything to a balance connector, just plug in the 10s. However, I would still put a separate switch in the 42v line because I don't want to turn the receiver on when I connect the 10s. Right now I'm using the balance connector tapped at 3s because the voltmeter has a limited range. I can still tell that the 10s is charged if I read 12.6 when I plug it in. At the end of the flight I read 11.1 volts.

The BEC that Flyer88 referred to in another thread looks like it should work as long as the voltage didn't exceed 8.4 volts. I picked 8.2 to be on the safe side and to be a little closer to the recommended storage voltage.

So far I like the high voltage servos but I'm not sure it is worth it to change over.

Jim O



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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 12:29 PM   
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quote:

ORIGINAL: Flyer88

Sometimes I just believe that less is more.......


The Western Robotics unit is just what I am looking for... don't have to wait for DE to make one.

I like the HV input to the BEC straight of the main pack wires (on the ESC connector side, of course) which eliminates the need to plug into a balance tap.



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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 5:06 PM   
jgg215


 

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Status: offline 		Thanks, Jim
I like your idea  of using 8.2 volts rather than 8.4. Don't believe you will ever have balance problems on the 2s doing that. I've never felt particularly overworkd by having to plug in the balance connector but anything that reduces cycles on connectors is a good thing.
I would like to add that there should be switches on both power sources. Easiest way to check that both power sources are good to go before takeoff. Otherwise you lose much of the advantage of having a redundant system.
There are some that would be horrifed that you are plugging in your motor battery before having an operational RF link.
John


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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 7:05 PM   
cmoulder


 

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quote:

I would like to add that there should be switches on both power sources


John, I am using an arming switch between ESC and main packs, so yes, both are switched. To verify that both are working, I alternate turning on the back-up battery first or the arming plug first.

Some may be horrified at this, and I was quite wary the first time I tried it and had a holder with a firm grip on it, but there has never been an issue with it.

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 7:24 PM   
OhD


 

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Status: offline 		From what I know about ESCs with optical coupling, there is no way they can be armed without seeing the proper sequence of pulses on the input. With the RC system off, it is not going to see that sequence. Further, it doesn't see that sequence when I turn on the radio, but only arms when I command it, after I check out all the other controls. When I do arm it, it is with the throttle cutoff switch so the motor can't start even if I advance the throttle. seems like a pretty safe procedure to me.

Jim O

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 7:30 PM   
jgg215


 

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Status: offline 		Bob,
That sounds pretty good. The only thing I can think of is IF you had an incorrect model selected on the TX which did allow arming of the ESC AND you had a bad failsafe set on that model AND you then noticed that the wrong model was selected AND you then turned off the TX without shutting done the airborne system.....
Thats an awful lot of whatifs for sure.
John


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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 7:46 PM   
jgg215


 

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I agree about the ESC not working until proper pulses are received and that the optical link should definely block any kind of noise signal. When we were going through the safety rule proposals earlier this year, there was an unconfirmed  report where someone could repeatedly trigger an ESC with the RX turned off by making a cell call. I never found out the specifics (ESC, radio, motor, cell phone, cell phone distance). I suspect that it was a cheap small ESC but I don't know. Assuming the story was true, I suspect this ESC was not optically coupled and somehow enough RF signal was generated on the throttle wire acting as an antenna to trigger the esc. Far fetched but more likely than divine intervention.
John


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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 7:51 PM   
OhD


 

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quote:

ORIGINAL: cmoulder


quote:

ORIGINAL: Flyer88

Sometimes I just believe that less is more.......


The Western Robotics unit is just what I am looking for... don't have to wait for DE to make one.

I like the HV input to the BEC straight of the main pack wires (on the ESC connector side, of course) which eliminates the need to plug into a balance tap.




Be very careful with the 8.4 volts if you use that output. LiPo cells don't like any overcharge. I'd hate to see your airplane go down in flames.

Jim O

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 9:00 PM   
pvogel


 

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Status: offline 		How do you program the jaccio switch to 8.2 v? the only ones I've seen are 5.7 and 6.0v

Isn't switching 10S down to 8.2v kind of inefficient? Won't the switching BEC be necessarily heavy due to the high frequency switching that has to go on? Why is tapping off the full 10S better than tapping 3S off the balance port?


Just trying to learn...
Thanks!
Peter+

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 10:32 PM   
Flyer88


 

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Status: offline 		Tapping the cells would put the main pack out of balance I would assume .
You want to have a balanced charge and discharge.

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 10:33 PM   
jgg215


 

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Status: offline 		Peter,
I believe there is an external voltage divider circuit that controls the output voltage so Jim just built one of his regulators with a new pair of resistors.  The switching regulator from Western Robotics is heavier than the Tech-aero or Jaccio but handles more current. They are very efficient.
As Bob said,, using 10S and a switching BEC means you no longer have to plug into the balance connector every time.

It occurs to me that once you have decided to use HV servos, there is a cheaper, lighter way. Connect a 2S line directly or wired through a switch to the motor battery balance connector and use a small lipo through a diode and a switch as backup. The diode provides isolation if you need it plus a voltage drop to keep the backup battery from sharing the load. Cheap and light.

John


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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 11:07 PM   
OhD


 

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quote:

ORIGINAL: jgg215

Peter,
I believe there is an external voltage divider circuit that controls the output voltage so Jim just built one of his regulators with a new pair of resistors.  The switching regulator from Western Robotics is heavier than the Tech-aero or Jaccio but handles more current. They are very efficient.
As Bob said,, using 10S and a switching BEC means you no longer have to plug into the balance connector every time.

It occurs to me that once you have decided to use HV servos, there is a cheaper, lighter way. Connect a 2S line directly or wired through a switch to the motor battery balance connector and use a small lipo through a diode and a switch as backup. The diode provides isolation if you need it plus a voltage drop to keep the backup battery from sharing the load. Cheap and light.

John



Using only 2s of the motor battery will give you some wild voltage variations (down to 7 volts) and might not keep the small lipo charged. The diode would have to be in that circuit to prevent the small lipo from supplying current to the motor. I still believe in voltage regulation even on HV servos.

Jim O

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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 11:18 PM   
jgg215


 

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Status: offline 		Jim, Good point about regulation. Oh well.



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RE: Simple redundant pwr. Battery + BEC. - 12/17/2012 11:23 PM   
jgg215


 

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Status: offline 		The 50 mah or so consumed by the radio in a single flight is insignificant and easily accounted for by a balance charger. Been doing it for the last year and a half without ill effect of any kind
John


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RE: Simple redundant pwr. Battery + BEC. - 12/18/2012 12:38 AM   
cmoulder


 

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quote:

Connect a 2S line directly or wired through a switch to the motor battery balance connector and use a small lipo through a diode and a switch as backup.


What diode should be used?

I think I understand it conceptually, and I know enough to make a good solder, but my knowledge of electronics is just enough to get me into deep trouble.

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RE: Simple redundant pwr. Battery + BEC. - 12/18/2012 1:00 AM   
cmoulder


 

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quote:

ORIGINAL: pvogel

How do you program the jaccio switch to 8.2 v? the only ones I've seen are 5.7 and 6.0v

Isn't switching 10S down to 8.2v kind of inefficient? Won't the switching BEC be necessarily heavy due to the high frequency switching that has to go on? Why is tapping off the full 10S better than tapping 3S off the balance port?


Just trying to learn...
Thanks!
Peter+




Hi, Peter:

Perhaps anecdotal, but I notice no difference in mAh consumption with BEC vs separate Rx batteries. Theoretically there must be some, but it is so little as to be insignificant.

No balance tap = one less point ot failure and one less thing to plug in before flying! I have had balance tap wires break after numerous fatigue cycles (plugging into the charger balance taps), so it is an issue to consider. Even with the VHV BEC I made sure that the section of the ESC wires (where the VHV BEC leads are soldered in) does not move around.

By the way, Dimension Engineering responded to my question and advised that they have no plans to introduce a VHV BEC for HV servos, so it seems Western Robotics is the only option for HV servos and BEC at the moment.

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RE: Simple redundant pwr. Battery + BEC. - 12/18/2012 5:23 AM   
OhD


 

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quote:

ORIGINAL: cmoulder

quote:

ORIGINAL: pvogel

How do you program the jaccio switch to 8.2 v? the only ones I've seen are 5.7 and 6.0v

Isn't switching 10S down to 8.2v kind of inefficient? Won't the switching BEC be necessarily heavy due to the high frequency switching that has to go on? Why is tapping off the full 10S better than tapping 3S off the balance port?


Just trying to learn...
Thanks!
Peter+




Hi, Peter:

- so it seems Western Robotics is the only option for HV servos and BEC at the moment.


Well no, not literally.

Jim O

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RE: Simple redundant pwr. Battery + BEC. - 12/18/2012 10:21 PM   
cmoulder


 

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Status: offline 		You're right. There is also the CC BEC Pro with up to 12S input, with output voltage adjustable up to 12v.

I googled and found another one (45 grams!).

I am referring specifically to the HV input units only.

Are there more offerings on the market for HV input and 8.4v output?

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RE: Simple redundant pwr. Battery + BEC. - 12/19/2012 12:44 AM   
pvogel


 

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quote:

ORIGINAL: jgg215

Peter,
I believe there is an external voltage divider circuit that controls the output voltage so Jim just built one of his regulators with a new pair of resistors.  The switching regulator from Western Robotics is heavier than the Tech-aero or Jaccio but handles more current. They are very efficient.
As Bob said,, using 10S and a switching BEC means you no longer have to plug into the balance connector every time.

It occurs to me that once you have decided to use HV servos, there is a cheaper, lighter way. Connect a 2S line directly or wired through a switch to the motor battery balance connector and use a small lipo through a diode and a switch as backup. The diode provides isolation if you need it plus a voltage drop to keep the backup battery from sharing the load. Cheap and light.

John



Yeah, I do that today (2S lines connected directly) using a PowerSafe Receiver with two lipo inputs. But I agree with others that you really want a regulated voltage so that the servos perform the same before, during and after flight even as the main pack is getting heavily used by the motor. I've wanted to go regulated HV for about a year but haven't found a weight efficient way to do it, was hoping the Jaccio to 8.2v + 3S balance tap would be the answer for the secondary side of my Rx (with the Rx bat on a reg set to something like 8.1v) so that the normal circumstance is pulling from the main pack and the Rx battery is just a backup.

Peter+

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RE: Simple redundant pwr. Battery + BEC. - 12/19/2012 6:27 AM   
OhD


 

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ORIGINAL: pvogel



Yeah, I do that today (2S lines connected directly) using a PowerSafe Receiver with two lipo inputs. But I agree with others that you really want a regulated voltage so that the servos perform the same before, during and after flight even as the main pack is getting heavily used by the motor. I've wanted to go regulated HV for about a year but haven't found a weight efficient way to do it, was hoping the Jaccio to 8.2v + 3S balance tap would be the answer for the secondary side of my Rx (with the Rx bat on a reg set to something like 8.1v) so that the normal circumstance is pulling from the main pack and the Rx battery is just a backup.

Peter+


I guess I'll build the 3s to 8.2 volt regulator for you and you don't need or want a regulator in the 2s circuit. See my block diagram. The 2s pack will be continuously charged to 8.2 volts while you are flying. I don't think you can get a redundant, regulated system any lighter than that.

Send me a PM with your address and specify the type of balance connector that you use.

Jim O

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RE: Simple redundant pwr. Battery + BEC. - 12/19/2012 2:53 PM   
nonstoprc



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Status: online 		Seems the backup LIPO (one cell in it) can be overcharged if it is continuously charged during flight without a balancer?

< Message edited by nonstoprc -- 12/19/2012 3:31 PM >

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