Battery Question

[JimiGibbs]

I purchased a Great Planes Fokker DR1 Triplane because it was being discontinued and I love that plane.... I'm still building up to it with a Super Cub LP. Anyway getting ready to start the build using the recommended ESC and Motor ([IMG]file:///C:/Users/Jimi/AppData/Local/Temp/moz-screenshot-2.png[/IMG]ElectraFly SS-25 25amp brushless ESC & ElectraFly Rimfire C28-30-950 brushless motor) and was wondering if the Super Cub LP batteries will work? It calls for 1250mAh 15C and the Cub's are 1300mAh 20C. From my limited knowledge I think it will but just want some confirmation......
Thanks,
Jimi

[Heli Jim]

The slightly higher mAh rating is ok--it's like a 12 oz fuel tank instead of a 10 oz. tank.
The 20 C instead of a 15C is fine too. No problems there.

The thing you have to be careful of is the number of cells (2S or 3S)
and/or the voltage required.

Does it call for a 2S or a 3S pack?

[JimiGibbs]

Thanks for the quick reply Heli Jim.... Both of them call for 3S 11.1V. I probably should have listed that.....
Thanks,
Jimi

[tampaflyer]

your fine...

[flydiver]

Battery as indicated is fine.
SS ESC OTOH I would not recommend if you haven't bought it. They use an archaic 67% LVC method that is not lipo friendly.
ElectraFly SS-25 25amp brushless ESC

For example (You know that LVC should be at MINIMUM 3.0v/cell? a bit higher is better)
On a full 3S = 12.6v
.67 x 12.6 = 8.44v/3(cells) > 2.8v (not so good)

Now, assume you took off, remembered something needing doing after a couple minutes, landed, and took off again a bit later thinking you only used up a couple minutes so would be fine. You have a good time and fly to LVC.
Assume voltage went down to maybe 11.9v
.67 x 11.9 = 7.97/3 > 2.6v
Now you are getting into the destructive range. Lower is just even worse.

The ESC works fine, the LVC is the lousy part. Just do not fly to LVC, ever, unless you have no alternative or could give a rip about your lipos.

Would a major brand name do this?
Yep, a number of ESC are poor this way.
Don't just take recommendations. Learn to read specs.

[JimiGibbs]

Thanks Flydiver.... I already ordered the ESC so I will just have to be careful. I understand what you are saying so it will definitely help on future purchases. Right now I am VERY NEW to this so I was just going with what was recommended.
Thanks,
Jimi

[solentlife]

Originally Posted by flydiver

.........
On a full 3S = 12.6v
.67 x 12.6 = 8.44v/3(cells) > 2.8v (not so good)

Now, assume you took off, remembered something needing doing after a couple minutes, landed, and took off again a bit later thinking you only used up a couple minutes so would be fine. You have a good time and fly to LVC.
Assume voltage went down to maybe 11.9v
.67 x 11.9 = 7.97/3 > 2.6v
Now you are getting into the destructive range. Lower is just even worse.

The ESC works fine, the LVC is the lousy part. Just do not fly to LVC, ever, unless you have no alternative or could give a rip about your lipos.
.......

This is a subject that has been beaten to death more than once and also shown to be generally misread data on ESC's.

Most ESC's will do as you illustrate when it's NiMH or old style cells ... but on LiPo, most will actually, even cheap ESC's, ignore the starting VOLTAGE of the pack ... and will LVC at the VOLTAGE set regardless of starting voltage.

When this was argued on another thread - I even tested MY version on my ESC's ... a 10A, 20A and a 30A ... all cut of at the set voltage regardless of starting condition - full charged, part charged. But the NiMH pack and ESC worked on % of initial charged state ...

Lets take HW30A for example ....


For lithium batteries, the number of battery cells is calculated automatically. Low / medium / high cutoff voltage for each cell is: 2.6V/2.85V/3.1V. For example: For a 3 cell lithium pack, when medium cutoff voltage is set, the cut-off voltage will be: 2.85*3=8.55V.
2) For nickel batteries, low / medium / high cutoff voltages are 0%/45%/60% of the startup voltage (i.e. the initial voltage of battery pack), and 0% means low voltage cut-off function is disabled. For example: For a 10 cell NiMH battery, fully charged voltage is 1.44*10=14.4V, when "medium" cut-off voltage is set, the cut-off voltage will be:14.4*45%=6.5V。


or the Mystery ..

　

2. Battery type
(Voltage Cut-off)
NiCad: . . . . .
2Lipos: (5.6V) .. .. .. .. ..
3Lipos: (8.4) … … … … …


(NiCD not showing numbers means it does not use a specific set Voltage).


So what I do agree with is setting LVC at 3.0V per cell minimum for Lipo cells ... but problem is many factory default settings are at 2.8V.

[flydiver]

Like I said, read the specs.

He bought the [Silver Serries]. That is how the SS behaves. I've read the full manual a dozen times.

The [LiPo Compatible Brushed ESCs] can be programmed for lipo. But their LVC is 2.75v/cell. It cannot be raised.
From the manual:
[Low Voltage Cutoff: 0.80V per cell for NiCd/NiMH; 2.75V per cell for LiPo]

IMO neither of these models is reasonably compatible with current generations of lipos. There are better products readily available. Why bother with this brand? It's more expensive and doesn't work as well.

It is beyond me why Electrifly didn't put even this residual lipo option in the SS series or if they did why they are so stupid as to not indicate so in their own specs/literature.

Tower want $33 for this 25A. They want $34 for a Castle 18A, a significantly better ESC.
If you are willing to not shop Tower then you can get a HobbyWing, 30A for $14 at Hobbypartz, also a much better ESC.

You cannot compare a HW30 (Turnigy) to an Electrifly to a GWS to a Castle.....etc. They are all different ESC.
You want to see old school awful LVC, check out the GWS, they are terrible, they still sell 'em, people still buy them thinking they are getting a superior brand name product.
Buy what you want but know what you buy.

[cliffh]

The battery is fine....but don't even think of flying this plane for a while

A triplane isn't exactly beginner friendly. Build it, admire it, use it as incentive to learn to fly well....then fly it.

It is too beautiful an airplane to crash......and a beginner will do just that.

Sorry to take some of the fun out of things for a while, but don't rush. You will be much happier in the end

Have fun!

Cliff

[JimiGibbs]

Thanks Cliff.... I understand. That's my plan is just to build it and let it sit for a while. I flew nitro planes over 15 years ago and when I decided to get back into planes I purchased an an E-flite Extra 260 but after reading more about it I decided to step back to the Super Cub trainer and simulator. I love the Tri and when I saw it was being discontinued I had to have one.......
Thanks,
Jimi

[solentlife]

Originally Posted by flydiver

Like I said, read the specs.

He bought the [Silver Serries]. That is how the SS behaves. I've read the full manual a dozen times.

The [LiPo Compatible Brushed ESCs] can be programmed for lipo. But their LVC is 2.75v/cell. It cannot be raised.
From the manual:
[Low Voltage Cutoff: 0.80V per cell for NiCd/NiMH; 2.75V per cell for LiPo]

IMO neither of these models is reasonably compatible with current generations of lipos. There are better products readily available. Why bother with this brand? It's more expensive and doesn't work as well.

It is beyond me why Electrifly didn't put even this residual lipo option in the SS series or if they did why they are so stupid as to not indicate so in their own specs/literature.

Tower want $33 for this 25A. They want $34 for a Castle 18A, a significantly better ESC.
If you are willing to not shop Tower then you can get a HobbyWing, 30A for $14 at Hobbypartz, also a much better ESC.

You cannot compare a HW30 (Turnigy) to an Electrifly to a GWS to a Castle.....etc. They are all different ESC.
You want to see old school awful LVC, check out the GWS, they are terrible, they still sell 'em, people still buy them thinking they are getting a superior brand name product.
Buy what you want but know what you buy.

Apologies ... it's a hang over of the spiel of the other threads ... I quickly read and assumed wrongly it was a repeat of 'general ESC misrepresentation' ...

When you quoted a re-flight with part discharged pack and the LVC etc. - I replied a little too quickly !!

I think you will agree though that most ESC's are not guilty of this bad set-up ... that most will act on the LVC setting of Voltage not % when it comes to LiPo. If as you say the SS is acting on % - that is terrible.

Again I apologise. As you say - it's worth buying better !

[cliffh]

Originally Posted by JimiGibbs

Thanks Cliff.... I understand. That's my plan is just to build it and let it sit for a while. I flew nitro planes over 15 years ago and when I decided to get back into planes I purchased an an E-flite Extra 260 but after reading more about it I decided to step back to the Super Cub trainer and simulator. I love the Tri and when I saw it was being discontinued I had to have one.......
Thanks,
Jimi

Okay Jimi, gotcha. That is a beautiful airplane and I'm sure you will like it. Hard to tell what "beginner" means

Since you are new to electrics though, let me add this. Like the nitro planes, you want to usually land with some throttle applied...in particular with that triplane. If you don't, it WILL nose over. Won't hurt anything, but it isn't graceful either

It is all to easy with electrics to attemp to land with the throttle all the way off.

Cliff

[kyleservicetech]

Originally Posted by cliffh

It is all to easy with electrics to attemp to land with the throttle all the way off.

Cliff

And with the power off, you've got a windmilling prop, that really creates a lot of drag. Nice if you need drag to slow the model for landing, not nice if you are stretching to reach the field.

[Lieutenant Loughead]

Originally Posted by kyleservicetech

And with the power off, you've got a windmilling prop, that really creates a lot of drag. Nice if you need drag to slow the model for landing, not nice if you are stretching to reach the field.

Ugh -- this is a never-ending debate. Does a windmilling prop have more or LESS drag than a prop with the brake on (NOT windmilling)?

I would have been very happy if you had not opened Pandora's box with your statement... :o

[kyleservicetech]

Originally Posted by Lieutenant Loughead

Ugh -- this is a never-ending debate. Does a windmilling prop have more or LESS drag than a prop with the brake on (NOT windmilling)?

I would have been very happy if you had not opened Pandora's box with your statement... :o

OK, how about a windmilling prop on an electric motor having more drag than a glow engine that is running at idle speed?

[Lieutenant Loughead]

You're comparing apples (electric with power off) and oranges (IC at idle speed). Therefore, I disagree with your statement that a windmilling prop creates a lot of drag.

It's amazing how my Stryker and Funjet can glide around for such a long time, while the prop in the back is windmilling. I've also had very good results with my GWS Zero, GWS P-51 Mustang, and GWS ME-109 gliding around with a windmilling prop.

HOWEVER, as soon as I turned on the ESC brake on the GWS Zero, I started having real problems.

Yes -- my data is from direct experience, and honest to goodness testing.

No -- a windmilling prop has much less drag than a prop that is stopped due to an ESC brake. In the electric flight world, those are your two options (or maybe a third is to use a folding prop). Please do not bring IC into the discussion.

[kyleservicetech]

Originally Posted by Lieutenant Loughead

You're comparing apples (electric with power off) and oranges (IC at idle speed). Therefore, I disagree with your statement that a windmilling prop creates a lot of drag.

It's amazing how my Stryker and Funjet can glide around for such a long time, while the prop in the back is windmilling. I've also had very good results with my GWS Zero, GWS P-51 Mustang, and GWS ME-109 gliding around with a windmilling prop.

HOWEVER, as soon as I turned on the ESC brake on the GWS Zero, I started having real problems.

Yes -- my data is from direct experience, and honest to goodness testing.

No -- a windmilling prop has much less drag than a prop that is stopped due to an ESC brake. In the electric flight world, those are your two options (or maybe a third is to use a folding prop). Please do not bring IC into the discussion.

That's why I used a folding prop on my 10 foot wingspan Viking sailplane in the mid 1980's. My original brush type ESC for the Astroflight Geared 40 motor, and 15 inch prop did not provide for a brake on the motor.

That windmilling prop made a BIG difference in the glide ratio of that sailplane, as compared to when a motor brake was added later on to fold that prop. That windmilling prop made that sailplane fly like the spoilers were up.

The energy required to spin that "draggy" brush type motor (with no power) has to come from somewhere.

Interesting point though. It won't take much to set up a Hacker A30 size motor with a 12 inch prop on a framework that allows measuring wind drag. Then aim my Hacker A60-16M motor with a 19 inch diameter prop at it from perhaps 5 feet away. That will allow direct measurement of drag both with the prop spinning, and stopped. Another project for the winter months around south east Wisconsin!

[Lieutenant Loughead]

LOL -- I've actually considered building a four-motor aircraft, with the two inboard motors powered, the port outboard windmilling, and the starboard outboard "fixed".

The idea is, whichever way the airplane wants to roll would be the prop with the most drag.

Unfortunately, I have never built that airplane for testing...

[kyleservicetech]

Originally Posted by Lieutenant Loughead

LOL -- I've actually considered building a four-motor aircraft, with the two inboard motors powered, the port outboard windmilling, and the starboard outboard "fixed".

The idea is, whichever way the airplane wants to roll would be the prop with the most drag.

Unfortunately, I have never built that airplane for testing...

Sir, you, like me, have far to much time on your hands LOLOLOL!

[cliffh]

Originally Posted by Lieutenant Loughead

(snip) Please do not bring IC into the discussion.

Why not? The original poster stated he had lots of experience with IC (glow) flying, but was new to electrics. I was pointing out a difference between glow flying and electrics. Good to know info.

If you attempt to land an electric triplane or many biplanes with the throttle completely off, it will most likely flip on landing.

I'll stay out of the brake on/off discussion other than to say I always use brake off.

Cliff

[Lieutenant Loughead]

Originally Posted by kyleservicetech

Sir, you, like me, have far to much time on your hands LOLOLOL!

LOL -- noted. However, to be fair, if I had too much time on my hands, I would have built it already!

Originally Posted by cliffh

Why not?

Because this is an ELECTRIC flight forum, and we are talking about props with the power OFF (which is something an IC engine can't do without a deadstick landing). Not to mention that a prop connected to an IC engine will be STOPPED (not spinning in the wind) the way an electric motor would allow -- this means far LESS drag for the electric free spinning prop, as opposed to the IC stuck prop.

Again -- IC is to electrics as apples are to oranges.

[cliffh]

Originally Posted by Lieutenant Loughead

LOL -- noted. However, to be fair, if I had too much time on my hands, I would have built it already!

Because this is an ELECTRIC flight forum, and we are talking about props with the power OFF (which is something an IC engine can't do without a deadstick landing). Not to mention that a prop connected to an IC engine will be STOPPED (not spinning in the wind) the way an electric motor would allow -- this means far LESS drag for the electric free spinning prop, as opposed to the IC stuck prop.

Again -- IC is to electrics as apples are to oranges.

You are getting too picky here. I fully understand this is an ELECTRIC forum here. I AM/WAS talking ELECTRIC here. I was mearly pointing out the difference between landing electric (notice the electric part here) and a glow airplane to help keep someone from flipping his new electric. Nobody bothered to tell me to land with some throttle on for many flights. I wish they had. This has nothing to do with drag. It has to do with preventing the airplane from stopping too quickly on the ground and flipping over forward. Someone who has only flown glow may not think about this. It mainly affects biplanes and triplanes.

The mere mention of the word "glow" or "IC" should not set off alarms or concern. I was pointing out the apples and oranges difference to someone new to oranges. I'm attempting to help a new ELECTRIC flier.

We need to all lighten up a little and enjoy our hobby.

Cliff