450 lipo bat

[Rico]

I have a small question about my lipo bat's, I notice that my batteries are a bit warm after flight and a little puffed, but when thy cooled down there is nothing wrong with them, dose that mean thy are about to be warren out or are thy still good, thy don't puff much, just so it feels like there is some foam in side them, is that normal or what.

Greetings Rico

 

[Tony]

That is "sorta" normal for a moderately used battery. New batteries that do this should be replaced with a higher C pack. But, it's nothing to worry about. Slightly warm and puffed is what mine look like when I get done flying.

 

[Derek]

Yeah...all of my batteries get slightly warm after a flight. Whether it's the lipo's being used on my Trex 500, my motor glider, my delta wing, my RCH Trainer, or any of my other planes. I do have some very minor puffing but nothing major. Just normal usage.

 

[Rico]

Hmm well I guess I don't have to be worried then, it was just that I saw on youtube a lipo explosion, and I don't think my wife would appreciate that kind a stunt in the house hehe, but I will get some lipo bags for them, my bat's are 11,1 v and 2200 mah and 20 C, I think thy are a bit little, I was thinking about 30 or 35 C, or are thy too big ??

thank you for a fast replay


Greetings Rico

 

[Derek]

If you were to get a higher C rating, like the 30-35 that you are talking about, the batteries would probably not get as warm as the 20C.

 

[Rico]

sweet then I guess I have to save up for some new batteries hehe

thx mountaindew

PS best pop in the world lol

 

[coolgabsi]

Look at the internal resistance of the packs


If they are coming back a little soft, may be turn the head speed down a bit and or flight time. Warm is ok. Soft or puffy means they are being over drawn.

May be the C rating isn't matched or as I said they have developed high internal resistance

 

[Rico]

Hmm I don't know how to measure the resistance of the packs, or to lover the head speed, some one told me once here in forum how to calculate the head speed, but I cant remember it, and I cant find the thread either

but I have been thinking about that my head speed might be too high, I all ready lower it from a 13 T pion to an 11 T pion.

so I hope that we can find a nice solution on this issue some how hehe

Greetings Rico

 

[coolgabsi]

ok post your motor specs here. with the battery rating (C rating 20C 30 C or so on) and gear ratio (main gear / pinion gear count).. And that will help you figure out if its pulling too much current.

Measuring IR of packs is a bit complicated, but the easiest method is to have a charger that measures that, so its plug , button press and done, instead of having to run that manually somehow.

13t to 11t is quite a drop. you might need the drop you might not. but always go one step at a time.. drop to 12t.. see how it does. you might not have to go lower..

let us know.

 

[Rico]

my bat rating is 20 C and thy are 11,1 V and 2200 mAh, and my pinion is 11 T and the gear is 150 T for rotor and the auto rotation gear is 106 T and the tail gear is 25 T I think,
my throttle curve in my TX is -100 -66,7 -33,3 0,0 +33,3 +66,7 +100 if I read the curve correct but it seems like when I get to 50 % throttle the motor wont take any more rpm, but I don't know if that is right, it is not easy to hear for the wind in the rotor blades, oh and the motor is a storm 3800 kv, and here are the specs for the motor ( http://www.helipal.com/esc-3800kv-twister-brushless-motor.html )

I hope that is the info you need

 

[coolgabsi]

Rico the throttle curve you gave us, is that for idle up ? Can I ask where did you get that info ? just curious.. as usually the throttle curves are a much shallower V curve on Idle up and normal more is straight line. If you need help with that, please let me know.

Motor is a 3800KV motor. Looking at the specs, the battries you are using are a bit lower power than what a 450 would make good power with. The motor can pull a max of 36A and your battery can provide a max burst of 20A. There is a definite mis match there. Depending on your flying, you can get away hovering and puttering around with these batteries, but I would be careful going any harder on these batteries, as they will not be able to supply the amperage the motor needs. If you are just in a hovering stage, they are just fine.

RPM:

(3800KV (motor KV) * 12.6V (full battery) * 0.8 (motor efficiency) ) / Gear ratio = head speed at full battery (at 100percent throttle)

(3800KV (motor KV) * 11.4V (recommended voltage of used battery) * 0.8 (motor efficiency) ) / Gear ratio = head speed at end of flight (at 100percent throttle)


Gear ratio is main gear count/ pinion

So that puts your Headspeed at :
Full battery: 38304/13.63 = 2808rpm
end of battery : 34656 / 13.63 = 2541rpm

That is at full throttle .. so if you run 60 percent throttle just multiply by 0.6 and thats your headpspeed (average)

at this point with the 20C packs, to make them not stress too much 11t is good. But if you get higher rated batteryes (35C or so) you might be able to get more power and headspeed out of them.. and they will be able to handle 12t pinion.

 

[Tony]

Correction to Gaba's calculations. If you are running a flat 60% curve, you STILL have to multiply by .8 and THEN multiply by .6. The .8 is what the motor is sucking up and is not using (loss in efficiency) and then the .6 is for 60% throttle. Hope this makes sense.

 

[coolgabsi]

correct.. I meant 0.6 (60 percent throttle ) multiplied to the final rpm number I posted as it includes the 0.8 eficiency in it

 

[Tony]

Yup yup, I know what you mean, but the way you typed it out, could get a little confusing to someone just learning of the calculations. Just covering all the bases. Go ahead, go off on me and tell me that I'm "not right in the head" hahahahahahaha. I know where you live!

 

[coolgabsi]

hahahahahahahahahahahahaahaha.... we all know that .. just dont say it..



just kidding

 

[Rico]

well I think I finally figured out how to upload a picture in here he he

the first one is throttle curve normal



and the second one is IDL



a friend of mine told me that the normal throttle curve should look like that, he didn't give me any numbers, just a drawing, so I have just been trying to make it like he draw it.
so I have no ide if it is the right curve I have, the curve I mention earlier to day vase curve normal, I only hover and make a pirouette once in a while, I haven't got to 3D flying yet

 

[coolgabsi]

If this is just to a 450 size heli... I would go with straight line curve 0-25-50-75-100 or in your radio's case -100 0 100 straight

In case of idle up that flat line in the middle is not for you .. Seems like someone is using an overpower motor (or a nitro motor) and using throttle curves instead of a governor .. All that said

Here is what you need the idle up to be at
100-90-80-90-100

Or similar

Right there you'll see a tremendous power difference

 

[Rico]

ok so i change the normal and idl up curve, I have 7 points in my curve settings, but I will upload a picture so you can see if I did it right

normal first.



and idl up



oh and by the way, my friend's heli is on battery too, so I will contact him and tell him that he's throttle curve is wrong, unless he is using some very big C rating lipo's