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Old May 13, 2013, 12:08 PM
Flying = Falling (Slowly)
dharban's Avatar
Tulsa, OK
Joined May 2004
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Scorpion Battery Backup

There have been several discussions here concerning the use of ESC's, BEC's and separate receiver battery packs. A few weeks ago Ed Franz furnished a line ot a Backup Battery system offered by Scorpion. I acquired one to test and am very impressed with its capabilities.

Of course, everyone is trying to solve a different problem with their setup, but mine was to furnish flight and radio power to an expensive plane that had very limited space for gear, a long nose which creates balancing problems and uses very small servos in the tail which, according to the manufacturers (Hyperion and MKS) should not be operated above 5.5 V. It appears that the Scorpion unit may offer a pretty elegant solution.

The Scorpion Battery Backup is a 2S 500 mah pack which also incorporates a linear regulator and a switching circuit. The device is plugged into an open receiver port and it becomes possible to use the BEC which is a part of your ESC as a primary source of radio power (be sure that the BEC on the ESC is a SWITCHING REGULATOR, not a LINEAR REGULATOR). If the switching circuit on the Scorpion device senses a voltage below 5.0V it will automatically switch on and furnish power to your radio system. In testing, this transition occurred seamlessly -- just like a computer UBS. So if you lose the ESC, the BEC or the flight battery, you have a good 38 gram backup.

To illustrate just what this device can do in some applications (actually my application), I'll walk you through the decisions I had to make and what their consequences were.

Alternative 1 -- use the BEC that was onboard of my Castle Creations ICE 80 BEC. Simple and straight forward, the BEC could be set for 5.5V and I would not threaten my tiny servos. BUT if the ESC, the BEC OR the flight battery failed, I would lose my plane. I am using a TP 1300 3S 70C for my flight pack and it is good for about 14.6 watt-hours. A typical ALES launch takes this plane about 4 watt-hours. So for normal flying (two launches on a battery) I have about 6.6 watt-hours of power reserve for the radio system.

Alternative 2 -- use a separate CC BEC connected as directly as possible to the flight battery. This adds about 11 grams of weight and, like Alternative 1, leaves me with about 6.6 watt-hours of power reserve for the radio system. In this case, a failure of the separate BEC or flight battery will result in a loss of the plane. (This is the system that I have used successfully for several years).

Alternative 3 -- use a separate radio battery connected to the radio system and isolated from the flight pack. I began using this system this year and it has been very satisfactory -- with qualifications. The radio battery I use is a Hyperion 1450 mah 2S LiFe pack. Based on measuring how much juice I put in it after a use, I think it has adequate flight time. But the battery tester I use does not really measure remaining capacity very accurately and so I am left with taking a battery which I "trust" to be good off the charger with a charge that the charger "says is good." In addition, if you have to use very small servos, you are likely to need a BEC to protect them. So my added weight for this system was 83 grams (battery) and 11 grams (BEC). This system increases the watt-hours of reserves for the receiver by about 50 percent to 9.6 watt-hours. But it still subjects me to the the risk of losing the plane from either a radio battery failure or a BEC failure.

Alternative 4 -- use the Scorpion Battery Backup. Using this system adds 38 grams to the Alternative 1 and does not require a separate BEC. The flight pack has about 14.6 watt-hrs of capacity and the Scorpion has about 3.5 watt-hrs of capacity. This gives me a total watt hours available to the plane of about 18.1 watt-hours. After two launches it still leaves a total reserve to the radio system of about 10.1 watt-hours. More than any of the previous alternatives, but more importantly, to lose radio power I have to have a failure of the ESC or flight battery AND a simultaneous failure of the Scorpion device.

Based on my bench tests, I will be trying the Scorpion in my latest installation.

Happy Landings,

Don

BTW: You can look at the Scorpion Battery Backup here:
http://www.innov8tivedesigns.com/pro...oducts_id=1154
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Old May 13, 2013, 12:40 PM
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Scotland UK
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Hi Don
I have read many of your posts with great interest, and also with considerable respect as to your input and knowledge .
For many years I used a separate 4.8 v battery pack, then changed to an esc with a high amp BEC. Now I use a UBEC to provide 5v.
I have never managed to move my thumbs at the speed of my servos even at 5v.
Could you please explain to me in simple terms that I can understand as to why I should consider High voltage servos etc.

Ian
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Old May 13, 2013, 01:13 PM
Flying = Falling (Slowly)
dharban's Avatar
Tulsa, OK
Joined May 2004
2,598 Posts
Quote:
Originally Posted by sandist View Post
Hi Don
I have read many of your posts with great interest, and also with considerable respect as to your input and knowledge .
For many years I used a separate 4.8 v battery pack, then changed to an esc with a high amp BEC. Now I use a UBEC to provide 5v.
I have never managed to move my thumbs at the speed of my servos even at 5v.
Could you please explain to me in simple terms that I can understand as to why I should consider High voltage servos etc.

Ian
I am not using high voltage servos or recommending them. If you use a separate battery pack for your receiver and it is a LiPo or LiFe, you either have to use servos that can take the higher voltage of these 2S packs or you have to use a regulator. The servos I use cannot take power from directly from the 2S lipo or LiFe packs.

As to why I do not use nicads or nimh packs, it is a matter of bulk, weight and reliability for my installation. The LiFe's work better.

As to why I don't simply take my power off of the BEC on the ESC, I have literally exploded an ESC and saved the plane only because the radio was not hooked up to the ESC.

If your plane has no real constraints with regard to space and battery placement, this is not such a big problem. But many of the molded planes have fuselages designed for F3J and are not well configured for placing batteries in places where balancing without adding tail weight is possible.

That said, having a truly redundant power supply in some of these expensive planes is very, very nice -- especially if you have ever experienced a battery or ESC failure.

Happy Landings,

Don
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Old May 14, 2013, 05:50 AM
mostly gliders
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Skellefteċ, Sweden
Joined Sep 2003
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Hi Don
Seems like a clever gadget, but it will be difficult to place it under the wing since powerswitch is positioned as it is? I wonder if it is possible to make an extension cable so you can place the power switch in the cockpit?

/Ville
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Old May 14, 2013, 06:20 AM
Flying = Falling (Slowly)
dharban's Avatar
Tulsa, OK
Joined May 2004
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Originally Posted by liukku View Post
Hi Don
Seems like a clever gadget, but it will be difficult to place it under the wing since powerswitch is positioned as it is? I wonder if it is possible to make an extension cable so you can place the power switch in the cockpit?

/Ville
It is not reasonably possible to place the power switch remotely from the device.

On the other hand, this is a very compact device. On my Maxas I am able to insert the flight battery back into the fuselage and then this device and have immediate access to the switch AND improve the balance of them without adding any weight. At least with the Maxa with servos in the tail, even using 1300 3S batteries for a 600 watt application, it is useful to cram the heavier flight battery as far back into the fuselage as possible. With the Maxa with servos in the nose, I use an 850 3S pack and it is still useful to cram it as far aft as possible.

This may not be true for every plane.

Happy Landings,

Don
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Old May 14, 2013, 06:52 AM
mostly gliders
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Joined Sep 2003
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Thank you Don for the reply.
It will be crowded in some of my planes, but I think it will be fine. There's shoehorn, right!

/Ville
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Old May 14, 2013, 06:59 AM
Flying = Falling (Slowly)
dharban's Avatar
Tulsa, OK
Joined May 2004
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Quote:
Originally Posted by liukku View Post
Thank you Don for the reply.
It will be crowded in some of my planes, but I think it will be fine. There's shoehorn, right!

/Ville
Yeah, maybe someday the guys that make our planes will be more thoughtful of the difference between a F5J plane and and F3J plane

Happy Landings,

Don
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Old May 14, 2013, 10:45 AM
mostly gliders
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Skellefteċ, Sweden
Joined Sep 2003
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I have ordered two Scorpion Backup Guard (SBG) for test. But at the same time I have become more curious about what makes it unique, if it is it?
What happens if I turn on SBG before the main system?
Can you determine if SBG has been used (via blinking LED or otherwise)?
Might not work so well as a backup for one more voltage fluctuating main system, such as when using such NiMh / LiFe?

/Ville
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Old May 14, 2013, 11:49 AM
Flying = Falling (Slowly)
dharban's Avatar
Tulsa, OK
Joined May 2004
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Quote:
Originally Posted by liukku View Post
I have ordered two Scorpion Backup Guard (SBG) for test. But at the same time I have become more curious about what makes it unique, if it is it?
What happens if I turn on SBG before the main system?
Can you determine if SBG has been used (via blinking LED or otherwise)?
Might not work so well as a backup for one more voltage fluctuating main system, such as when using such NiMh / LiFe?

/Ville
It is a linear regulator with a circuit that switches to the backup battery if the voltage drops below 5 volts. I am using a 3S 1300 mah flight pack which in my testing never drops close to 5 volts unless something is VERY wrong. I will set the BEC on my CC ESC at 5.5 volts to give me a little headroom for a voltage drop on the radio system. But inasmuch as the ESC has plenty of voltage AND capacity feeding it, it should not drop below 5 volts output unless there really is a problem.

I haven't tested it enough to know whether it gives you a signal when it has turned on, but it will blink if its capacity runs below 30 percent. I guess my feeling is that it will give you more security than simply blind faith in a BEC/Battery combination or a separate receiver battery that has less reserve than the combined flight battery/backup battery.

Happy Landings,

Don
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Old May 14, 2013, 12:01 PM
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Thank you again Don for the reply.

/Ville
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Old May 17, 2013, 01:09 PM
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So... if I only use standard (i.e.- non HV) servos and am running the Scorpion Backup Guard, it will switch power to the receiver using its' own internal lipo, if/when the BEC output falls below 5V.

1. Is the Scorpion Backup Guard a latching type system, that will continue to provide the receiver with its' internal lipo's voltage, evn if the main battery 'recovers' (i.e.- again provides a voltage greater than 5V) - or -

2. Will the Scorpion Backup Guard switch back to the standard BEC output (i.e.- the main onboard battery) when and/or if that battery recovers sufficiently to again provide greater than 5V output? This would in essence provide a somewhat of a "Brown Out" protection.

As liukku mentioned, can one actually see if it has been "actuated / used" aside from the blinking LED showing less than 30% power remaining?
Thanks
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Old May 18, 2013, 07:52 AM
Flying = Falling (Slowly)
dharban's Avatar
Tulsa, OK
Joined May 2004
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Quote:
Originally Posted by CoolCanuck View Post
So... if I only use standard (i.e.- non HV) servos and am running the Scorpion Backup Guard, it will switch power to the receiver using its' own internal lipo, if/when the BEC output falls below 5V.

1. Is the Scorpion Backup Guard a latching type system, that will continue to provide the receiver with its' internal lipo's voltage, evn if the main battery 'recovers' (i.e.- again provides a voltage greater than 5V) - or -

2. Will the Scorpion Backup Guard switch back to the standard BEC output (i.e.- the main onboard battery) when and/or if that battery recovers sufficiently to again provide greater than 5V output? This would in essence provide a somewhat of a "Brown Out" protection.

As liukku mentioned, can one actually see if it has been "actuated / used" aside from the blinking LED showing less than 30% power remaining?
Thanks
It is not clear whether or not the Backup Guard is a latching type system. I am assuming that it is, but I am not particularly concerned whether or not it is in this application.

The ALES/F5J application is one where we are trying to minimize the size and weight of the power system while providing adequate reserves against loss of power from the flight battery AND providing security against the failure of the ESC and/or the flight battery. And this is with a control system which uses small servos which are pretty much incapable of imposing more than a couple of amps even in surge situations.

Flying with a switch which limits the motor run for a single launch to 30 seconds allows a person to ration the power withdrawn from a battery pack pretty accurately. Depending on the size of pack I use, I know that a healthy pack will have at least 40 percent of its capacity remaining after either two or three launches. In addition, I have done enough bench testing of the Thunderpower 65C packs that I use to know that, except for a faulty pack, that there is no combination of power and control power than I can generate within the system AS LONG AS I OPERATE AT LESS THAN ABOUT 55C where a 3S pack will drop its voltage below 7.5 volts. If a 3S pack goes below 7.5 volts under the loads that my ALES planes impose on the system the most likely cause is a faulty battery. And 7.5 volts going INTO a switching ESC will always result in an output voltage in excess of the 5 volt cutoff for the Battery Backup. In this case, I am perfectly comfortable switching over to the backup and not worrying about whether the flight battery rebounds or not.

Before trying the Battery Backup, I used a separate BEC connected as directly as possible to the flight battery. This always worked well, but I am careful with my flight batteries and have never experienced a cell failure which would cause a loss of power to the control system. I switched to using an entirely separate LiFe battery pack for the control system and THAT worked well other than the fact that I could not accurately measure the remaining capacity in a LiFe pack and had to rely on my estimate of flying time and the reliability of THAT battery.

The Scorpion Battery Back-up provides a true redundant backup and it uses a LiPo battery for which I can, more or less, measure remaining capacity accurately. While it does not give an indication of whether it was actuated on a particular flight, it IS possible to determine if it has taken a hit by simply measuring its remaining capacity with an inexpensive battery meter.

I have concluded that the key to reliable operation starts with using good quality components, to stick with 3S or larger flight packs and size your flight packs so that they will not have voltage drops under load that will take you too close to dropping a BEC or control system off line. I am using Thunderpower 65C (and now 70C) flight packs because they have proven repeatedly in rigorous testing to have substantially lower voltage drops than other packs that purport to be 65C packs. And I generally do not take these packs above 55C in my applications.

Happy Landings,

Don
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Old May 18, 2013, 11:08 AM
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Don,
thanks for letting me know.
I'm not using it for ALES (at this point), however, I'm planning on using it on my 2.1m Simprop Excel Competition (yep, the old, old kit from '94). I'm currently running it on a 2C pack, getting unlimited vertical, as long as I can keep enough down elevators. It will go vertical on about 50-60% power.

I'm seeing 5-8 minute motor run times, depending on how much full-throttle power I use. So this gives me around 1 hour - 80 minutes in clean air total flying time.
I've noticed that once my ESC's BEC cuts in and makes it "a sailplane only", I typically only have 350 - 450mah left in the lipo's (3000mah 35C) after finally landing.

Therefore, I'm planning on using the Scorpion Backup Guard to give me a little leeway here, just in case I do find another thermal.

I'm just getting back into the hobby after a 20yr hiatus, so this is really fun, especially with all of these new components. I was able to take 460g out of the airplane this year (compared to last year's version), just by going from a 4C pack and larger 3548 motor (with a 10,5x6) and replacing it with a 3536 on 2C, running a 13x6,5 prop. I also dispensed with the GP 2700 receiver pack, which I previously needed for balance. And last years was already 400g+ lighter than the design weight (albeit with NiCD's), with much more power.

So now I'm flying it at 1046g all up, getting like 1670g thrust according to DriveCalc. All in all, I'm happy.

Come to think of it, maybe this will make a somewhat half-decent ALES after all...
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Old May 18, 2013, 11:45 AM
Flying = Falling (Slowly)
dharban's Avatar
Tulsa, OK
Joined May 2004
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Quote:
Originally Posted by CoolCanuck View Post
Don,
thanks for letting me know.
I'm not using it for ALES (at this point), however, I'm planning on using it on my 2.1m Simprop Excel Competition (yep, the old, old kit from '94). I'm currently running it on a 2C pack, getting unlimited vertical, as long as I can keep enough down elevators. It will go vertical on about 50-60% power.

I'm seeing 5-8 minute motor run times, depending on how much full-throttle power I use. So this gives me around 1 hour - 80 minutes in clean air total flying time.
I've noticed that once my ESC's BEC cuts in and makes it "a sailplane only", I typically only have 350 - 450mah left in the lipo's (3000mah 35C) after finally landing.

Therefore, I'm planning on using the Scorpion Backup Guard to give me a little leeway here, just in case I do find another thermal.

I'm just getting back into the hobby after a 20yr hiatus, so this is really fun, especially with all of these new components. I was able to take 460g out of the airplane this year (compared to last year's version), just by going from a 4C pack and larger 3548 motor (with a 10,5x6) and replacing it with a 3536 on 2C, running a 13x6,5 prop. I also dispensed with the GP 2700 receiver pack, which I previously needed for balance. And last years was already 400g+ lighter than the design weight (albeit with NiCD's), with much more power.

So now I'm flying it at 1046g all up, getting like 1670g thrust according to DriveCalc. All in all, I'm happy.

Come to think of it, maybe this will make a somewhat half-decent ALES after all...
I think you are referring to 2S packs, not 2C packs. I do not have anything against 2S packs except they can have voltage drops if highly loaded which can take you to close to not having enough voltage for the BEC. Most of my planes fly with between 400 and 800 watts and I like 3S and 4S packs because they keep the amps in the range that fits a little bit smaller ESC.

As far as selecting 2S, 3S or 4S packs, there is no "right" answer except that the battery has to fit the motor,gearbox and prop selection you have. I have a power setup for my Maxa which runs equally well with an 18x13 on a 3S pack or a 14x10 on a 4S.

Where reserve power gets a little more critical is an ALES application where you are shooting for a minimum weight power system. My setups will use about 60 percent of the pack capacity with a total motor run time of 1 minute. I push my batteries hard, but the one thing I do not do is to discharge them deeply. Just my opinion -- I would not run a flight battery down past about 30 or 40 percent full simply to help extend battery life. When I have run my packs down to the ESC cutoff, I seldom have more than 10 or 15 percent of the capacity left.

Happy Landings,

Don
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Old May 19, 2013, 03:00 AM
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Thanks

Thanks and yes, I did get the "C" and "S" mixed up there...
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