How to do parallel charging ?

Hello again.

I bet you searched this post because you are tired of waiting x minutes multiplied with the number of batteries you have…fair enough...

Same was in my case. So, let’s talk about parallel li-po charging.

First you must understand that a li-po is basically a 3.7 V nominal voltage cell, so if you have a 3 cell li-po it is 3.7Vx3cells.

The fully charged voltage, is of 4.2 V per cell, so a total of 12.6 V. The lithium –polymer(li-po) batteries can be hooked in serial or parallel configuration (for example S or P, like 3SP1 which is same as 3S)but this is something already inside the battery, so it’s just a coding for understanding it.

Normally since the li-po batteries don’t like to be left depleted it is strongly suggested not to drain more than 3.8 Volts from each cell, otherwise in time they will not last long.

Now, to the real thing: you must understand that you are responsible if something goes wrong, and I am not to be held liable for anything related to your parallel charging…

From my experience I can tell you that if you use different charged level batteries, you can have problems, personally my balanced connector melted on a small 1050 mAh battery !

so be carefull to put only same battery type and same charge state battery(not fully depleted and fully charged together).

First of all you need a good balancing charger and a good power supply, and additionally you need a balancing charger board, personally mine can charge up to 6 packs.

Since you will charge in parallel, you must keep in mind that by doing this the voltage stays the same, but the Amp power(capacity) is added for each battery you want to charge.

For example: I want to charge 3 x 2200 mAh batteries….first I check the voltage to be similar, but since I fly my 450 heli and land when the timer shows 5 minutes, they should be very similar in voltage….Then I usually connect the power plug and balance plug for each battery, and when all are connected, I plug the balancing board power socket to my charger, and lastly I plug the balancing connector to the charger. With all this in place I check again the wires and charging board for abnormally hot areas and only if all is ok, I connect the power supply to the charger. Next, I select Li-po from the menu, 11.1V and this is important, you must select the charging current as the sum of all the cells you charge, in my case 2200+2200+2200=6.6A for 1C rate. If you have really strong supply and charger, you can charge your batts at 2C capacity, meaning 13.2A, but I don’t recommend this unless your parallel charging board is really top quality, otherwise you might burn it.

So, another quick example: I want to charge my Master CP batts, which are 3s at 1050 mAh. After carefully connecting them on my parallel charging board, I select Li-po, with 11.1 V and charging current will be 1050+1050+1050 which is 3150 for a 1 C charge rate. Usually I choose 3.2A. simple, right?

Just in case you didn’t know, each Li-Po battery has a supplier recommended charge rate, and for 1C it is the battery’s capacity, for 3 C is 3 times capacity(2200 with 3C, allows me to safely charge it at 3x2200=6.6A). If you have no specification on yours just play safe and charge it at 1C, meaning charging current should equal you battery capacity.

Also the batteries have a discharge rate C value, usually between 10c to 60 C with 5 units increase. The highest the C value the more current it can give and the faster it can be depleted.

For example if you have a 10C battery and you need 20C in your heli setup, the battery will get extremely hot and possibly after doing this one time, you can throw it out the bin.

Usually for a 450 size heli it’s recommended to have a minimum 20 C battery, and if you plan really hard 3D with it, you should consider a 30 or 35 C pack.

Keep in mind again:

You are the only responsible person if something bad happens;

Only parallel charge batteries of same type(only 3s, only 4s, etc) and charge state

After connecting your batteries to the parallel charging board, check if wires, bord or batteries get hot, if not, proceed to connecting the charger;

Select same voltage as a single battery, but charging current equal to the sum of your charged batteries capacities (for example 2 each 2200mAh- select 4400mAh)

ALWAYS supervise the charging, never leave parallel charging unattended

Be safe, since li-po are quite sensitive batteries.

Below is the movie I made for a better understanding of the process.

Pffff, sorry for the long explanations, but I hope it was worth reading, and now you can say you know more about the “juice” we use in our beloved hobby.

Thanks for reading, and happy flying

Trex heli size comparison

Hello again,
Since there are more standard sizes out there, I will point out the most common size format for the Rc Helicopters, which is used by Align. According to their size chart you can have the following heli classes:

• 100 size class - usually rotor diameter is 192mm
• 250 size class - usually rotor diameter is 460mm
• 450 size class - usually rotor diameter is 710mm
• 500 size class - usually rotor diameter is 970mm
• 550 size class - usually rotor diameter is 1188mm
• 600 size class - usually rotor diameter is 1347mm
• 700 size class - usually rotor diameter is 1562mm
• 800 size class - usually rotor diameter is 1780mm

Align T-rex size chart for Rc helicopters

Of course there are some intermediate size heli's against the Align Trex chart, like for example the 125 size micro helicopters, like the Walkera Dragonfly, then the Walkera Master Cp which is more of a 200 class heli, and there are also the E-flite Blade 300 and 400 sizes hel's but let's just say these are some exceptions :)
Personally I have 100 size, my Genius CP V2, reviewed here which I find very good for indoor practicing in my living room, but also outside; then my Walkera Master CP which is more of a 200/250 size heli, also stable and good learning tool, since it is built to handle crashes-definitely not a living room flier, and lastly, for now, my RCX450 CF similar to the Storm heli, which I converted from flybar to flybarless.
According to each one's budget you can get the heli you want, of course the bigger the class, the better in terms of stability, but more expensive would be the "maintenance fee"  for it.

Another more "general" classification is made based on the weight and rotor diameter of the heli, as follows:

• Sub-micro (under 100g,  less than 200mm rotor diameter);

• Micro (under 500g, less than 500mm rotor diameter) - a 250 size heli is in this category;

• Miniature (under 1kg, less than 800mm rotor diameter)-usually the 450 class is here;

• Small (under 2kg, less than 1000mm rotor diameter)-the 500 size heli is in this category;

• Normal (under 4kg, less than1500mm rotor diameter)-the 600 size heli is in this category;

• Large (under 6kg, less than 2000mm rotor diameter)-both 700 and 800 size helis belong to this category.

Hope this info is helpful, since when I started this hobby the sizes was a very confusing topic to me...
Thanks and happy flying to all,

Throttle and pitch curves tutorial

Normal mode with Pitch in blue and THR in pink, L stick is at 0, M is at 50 and H is at 100.

Hello again,

I know there are a ton of info on the web regarding this topic, but I will try to explain in a more beginner friendly manner.

Let me start with the assumption that you have a digital transmitter with the function that allows you to acces throttle and pitch curves, and that you mechanically did your swash and pitch to be on 0 at mid stick.

Ok, now to the theory part :)

As you might now, the simple 4 channels or even coaxial rc helicopters have the throttle on the stick and nothing more…Switching to the 6 or more channels heli, things change a bit, and let’s start with the name:

CCPM ?! if you wondered what this stands for, it translates to Collective/Cyclic Pitch Mixing and with this you can give both throttle input and also cyclic input in one transmitter channel…Nice… When I first bought my Esky Belt CPX, I remember somebody telling me that the best up-grade I can do to it is not metal rotor head, but a digital TX, boy he was right.

Now, you already know some basic things, which is good, and I will explain about these curves, but first:…

You must also understand that the 6 channel heli’s have at least 2 flight modes : Normal and Idle up mode (or sport, 3D etc…); some TX have more than 1 Idle up mode, for example my Walkera Devo 10 has 2 IDLE up modes first one for just simple flight, second one for full 3 d flight.

Normal mode is used most of the times for hovering and taking off/ landing most of the time, and Idle up is used for forward flight and 3d flight, meaning all kind of nice aerobatics that a heli can do over a plane.

It is important to understand the available flight modes, because based on this you will set-up the throttle and pitch curves for each of them.

Ok, enough info, let’s get to real business here…First, we will look on the normal mode since it is the place to start with, so to speak.

As you know there should be a minimum of 3 points for any throtthe or pitch curves, more high-end radios have 17 points or more, but we are not 3d world champs, yet :)

You need the lowest position of the throttle stick, usually named “L”, then the medium position, usually named “M” which is exactly at the mid-stick position, and the highest position of the stick named “H” where your motor is at maximum power output. You can define, exactly how much throttle you want for each of these three positions, and the transmitter will calculate the connecting points with a straight liniar line, so you don’t have to worry about it. Now depending on how you wish to have it , you might have 0% throttle at L, (for example in Genius CP heli, at 0 and no throttle subtrims to lower maximum position, the motor will start) or negative throttle value, using throttle subtrim which I recommend and is safer. Also for H position, I don’t recommend keeping it to 80-90% max, since the ESC will not like it too much, better option is to use a smaller motor pinion if your head speed is too high. It may seem complicated but it is actually simple and I hope it makes sense so far. You can find many examples on different THR curves, I am focusing on making you understand how things work. Ok, enough with throttle curve for normal mode, let’s talk about idle up. In IDL up mode the throttle curve is at 100% maximum values at each L or H stick position, and anywhere between 50 to 100% at mid stick. This means you have full power at the ends for fast lift and down speed, but a bit milder in the middle since this is the point where in IDL up the pitch curve is changing. You can understand how THR curve works better from below diagrams: 

IDL 1, with -3 deg pitch at L stick, 0 pitch at M and +11 at H stick. THR curve is pink with with 100% at L and H and 85% at M stick

IDL 2, with -11/+11 pitch at L/H stick, and 95% THR at midstick, usefull for hard 3D flight

 

Ok, now a quick summary: Normal mode, you have 0% or better -10% throttle on the L stick, and based on preference maybe 50% THR on M and 100% on H stick

For IDL up you have -100% on L stick, 50-100% on M and 100% on H stick

One more mention before moving on to Pitch curves, about governors. This is a nice feature that some ESC have, and by enabling this, you have constant head speed, kind of similar to a cruise control in your car…you set it up to a value, and the ESC will try keeping it to that(usually 100&) no matter what motor load you have.

Now, moving on to my favourite part: the pitch curves.

As you already know, on a 6 channel CCPM heli, by moving the throttle stick, you also change the blades pitch, that create lift, either positive or negative. A good way to observe the pitch changing is by UNPLUGGING your motor, or by setting up Throttle hold pitch curve to have -11 to +11 degrees pitch at L and H stick positions, and then you can safely observe the blades pitch change with throttle stick movement.

So, again, in the normal flight mode, I suggest having around -2 or -1 degrees pitch al L stick, enabling you to land even in stronger winds that will lift your helicopter, and slowly transition to 0 pitch at M stick, and finally +100% pitch at H stick. Many people don’t do this, and have +1/+2 positive at L stick, maybe 5 degrees at M stick and +11 degrees at H stick. Having this, when you switch to IDL up mode with the stick in M position the heli will jump down because of the pitch difference… I recommend that after M stick position, the pitch curves to be identical for Normal and IDL up flight modes like 50% - M and 100% H stick. An usual IDL up curve for 5 points transmitter would be 0%-L 25% 50%-M 75% 100%-H, meaning you have maximum negative at L stick, 0 at M stick and maximum positive at H stick.

If your transmitter has the pitch range from -100% to +100% then the -100% should be considered as you maximum negative pitch setting, 0 should be set for M stick and +100% should be the maximum pitch setting. The main difference for IDL up is that as you remember for maximum stick positions, L and H you have maximum throttle for the motor, also for the same L and H you should set-up to have maximum pitch to match with the throttle curve, enabling you for example to have enough lift for upside down flight. Personally, I have IDL up 1 where I only set-up -3 negative to +11 positive at both ends, this is allowing me to do nice forward flight and circuits, and -11 negative to +11 positive in IDL up 2 for upside down flying and hard 3d.

I really hope that it is all clear for you now, and it will help you understand how you can set up your own curves based on your own preference and liking.

Until next time happy flying and blue sky !

Using Devo receiver on non walkera heli

             Hello All,

A good thing happening, is that Walkera seems to improve the quality of their products, anong wich the relatively new transmitter, the DEVO 10. I decided like probably many other to trust this TX and use it on my bigger size heli(450 size) and not only on the Walkera heli’s like my Master CP or my Genius CP V2.

So far no issue, and no regrets, only downside would be a limited amount of “how to” info’s compared for example with Spektrum or Futaba gear.

Since I struggled a bit, to figure out the connection settings and setup for my 450 build using my Devo 10 and RX-1002 receiver, I think somebody else can find this info as useful, and I will explain below how I connected everything for a 6 channel CCPM helicopter, in my case the elevator being in front of the swashplate…

ELEV : connect the elevator servo,
AILE : connected the front left servo
THRO : connected the ESC
RUDD : connected the main GYRO wires
GEAR: nothing connected here (in my setup, I assigned the AUX2 for Gain, and the MIX switch since it has 2 position for setting up)
AUX 1 : connected the right servo or pitch channel
AUX 2 : connected the gyro gain wire(single wire)

One important thing to look after is the orientation of the pins, since on some servos it is white or yellow wire which is assigned for the signal wire (you need this later if you convert it to flybarless like my case), the power is always the red colour wire in the middle, and the negative is the black or brown on some other servos.

You must connect always with the white (signal wires) towards the receiver label, and also my advice is to use a foam on the frame to fit the receiver on, without tension in the wires.

I hope this short guide was usefull to you , and until next time I wish you all happy flying and blue sky.

Dual rates and expo - how to ?

Hello again,

Some time ago when I first got my 6 channel “real heli” the Esky Belt CPX, many guys on the forums told me the best upgrade I could do

would be getting a programmable digital transmitter. Instead of that suggestion, I was planning to mainly upgrade to metal components in the rotor head.

Some time later, I finally got a Walkera Devo 10 transmitter, and now I realize what a huge difference there is compared to the non-programmable TX from Esky.

Because I will make a review of the TX later on, I just want to explain about the most important, maybe, settings that can help a beginner into Rc flying, whether

this would mean helicopter, plane or glider : Dual rates and exponential…

So, what does dual rates mean ? As you probably know already, all the stick movements we make into the transmitter, go into the receivers from our rc models, and

get translated into servo movements… Of course the servo arm that in our case is connected to the heli swash plate or the plane ailerons/elevators will move to maximum

positions for the maximum stick movement, right ? I hope it’s simple and understandable so far…The problem for a beginner is that maximum servo arm movement moves the

swashplate to the maximum position, and then the heli moves so fast, that for a beginner might take too much time to counter it, and crash….

Here the dual rates come into play…On the transmitter you can set the maximum travel of the servo arm, for example 70 or 80 % usually….This means that for the same

full stick movement the servo arm will move only 70 or 80% of his maximum travel, making our model move a bit less than with normal 100% servo travel…

On the Devo 10 you can set aileron dual rates, elevator dual rates and also rudder dual rates which is all you really need.

I hope you could understand my explanation so far…now let’s move on to the exponential settings…

For this one we should go back some time during the math lessons, because this is basically what the expo curve is…

It works very simple: in the defined area in the transmitter, the sensitivity can be increased by adding “-“ or negative expo, like world champ pilots use,

or in our case we want to reduce sensitivity for usually aileron and elevator by adding positive expo values, and then we have a curve like below…

Important thing is that after the stick gets ouside of the expo area, it will still move linear like you can see, only difference is that it is less sensitive in the

central area…For example I use my servo dual rates travel on my 450 helis to 80% and I set-up also exponential curve values to 15 or 20%.

On smaller size helis, like micro helis, many people use dual rates of 70% servo travel and expo values between 30-40%, but it depends on personal preferences.

Positive expo to reduce sensitivity around center stick

Negative expo that increase sensitivity around center stick

I hope I really made it simple and easy to understand...If you have any questions, please post your comments below.

Happy flying and see you next time