exeter_acres

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Question for ya'll

Flying a Zagi with a Mega 1615/4 and a CC P25 ESC

I like to fly it with both the stock 8 cell 1800mAh NiMh battery that comes with the Zagi and a Kokam 2000mAh 3S1P pack.....

When I fly with the Lipo I set the voltage cutoff in the ESC to 9v and all is good, but if I try to fly with the NiMh it cuts off immediately...

so I reprogram the ESC to 5v cutoff that is recommeded for 8 cell NiMh....

Here is my question...
If I am off at the field and don't want to re-program the ESC (OK..I admit it! I couldn't figure out how to program it with the TX so I use the USB hookup[])


But....
If I set the cutoff at 5v and just left it there and whenever I fly with the LiPo battery I use the timer on my radio (I have flown it several times and know how long of a flight I can get with plenty left over) and just made sure to land when time is up...would that be OK??

I know it is not recommended to set the cuttoff below 9v, but it would make my life sooo much easier!

Does my question make sense?
Your thoughts??

Thanks!
Exeter

Commander_Drake

My Feedback: (2)

exeter,

You don't have to reprogram the esc but it's good insurance. If you don't, you have to measure the voltage on the LiPo pack after each flight and if it's below 9.0 Volts you should discard it. My first plane with LiPo's I did not have an esc with the right cutoff voltage but even after long flights I was nowhere near 9 volts for the pack so I just kept checking after each flight and all was well.

bemyself

Hi all,
Can someone please tell me what's a ESC?? What is the function. the reason I ask is because I'm about to set up my new electric PA-18 cub Piper. The requirements are:
1. 350C gear drive motor
2. Speed controller
3. Batteries 830 mah
So, I don't see any ESC on this requirement and if I were to use Li Ploy batteries, what will be the recommended Voltage considering that the Mah is 830. Can I go for a higher MAH?
My LHS said that the batteries need to be connected to the speed controller first and then the speed controller to the receiver. If not, it'll burn the receiver because of the voltage from the batteries.Is it true? Please help as I'm very poor in electrical connection.
Your help into this matter will be greatly appreciated.

Commander_Drake

My Feedback: (2)

ESC stands for Electronic Speed Controller, looks like you have one.

Your batteries are 830 mAh but you did not say how many cells you are using or what the total voltage is.

NiCd and NiMH cells are 1.2 volts each and LiPo cells are 3.7 volts. If you have a battery pack with 5 NiCd cells in series thats 5*1.2 = 6.0 volts. The closest approximation in LiPo cells would be 2 cells in series = 7.2 volts.

Yes the battery pack connects to the ESC and the ESC provides the proper voltage to the receiver and voltage to the motor that you control with the throttle stick on your transmitter. The ESC will also shut off power to the motor when the battery starts to get low so that your receiver will still have power.

Hope this helps. Keep searching and reading in these forums. You will get a lot of info.

bemyself

Hi Commander Drake,
Thanks for the information. Do you think a Li Poly 7.2 volts ( 1 battery of 830 mah)will be sufficient for my set up. If I were to use 4x 1.2 NiMh( 1 battery of 2300mah ) will it be sufficient?
One last question. What are the things that will tell you that you have enough or not enough voltage to run the whole setup? I believe the mah is secondary while the voltage is primary. I appreciate your help in helping to explain a little further in terms of electrical setup.
Thanks

Commander_Drake

My Feedback: (2)

Hi bemyself,

It might be better if you post this question in the "Training" forum under "Electric Aircraft Universe". I would also recommend you read the electric FAQ at the top of the "General Electric Discussion" forum.

If your plane is designed for 4x 1.2 NiMH then I would stick with that for now. One LiPo might not be enough voltage and two might be too much. It depends on a lot of things.

Basically the mAh rating of the battery tells you how long a flight time you can get (ignoring extra weight, twice the mAh will give you twice the flight time). Voltage tells you how fast the propellor wil turn (in an ideal motor, twice the voltage will spin the prop twice as fast).

As far as the relationship between Volts, Amperes, Ohms, Watts, and mAh there are plenty of electrical references around to get that from.

Good luck.

bemyself

Hi Commander Drake,
thanks for the information.
P/s : you look great with the yellow plane beside you

raabid

Programming the CC is very simple with the TX, and the Voltage cutoff is the first feature in the program. I have the six voltage settings memorized and can change from 2s to 3s in about thirty seconds.