Voltage Drop Problem

[chipbury]

Hello,

I am suffering very quick voltage drops on my 450XL. I am having trouble setting the throttle curve correctly to allow me to fly without setting off the LiPo saver alarm in sometimes less thean 1 minute.

My setup is as follows:
Standard 3200KV motor with 13 tooth pinion.
Standard 25A ESC.
Standard 325mm yellow fibre blades.
Custom idea HR Poly X LiPo saver alrm set at 9v.
Flight Power 20C 3S batteries (one 70 cycles the other 50 cycles).
Prodigy Pro Peak II charger with Flight Power Balancer.
Mechanical pitch -10 to +10.
Tx Pitch Curve 40 40 50 75 100 (-2 -2 0 5 10 approx).

Can anyone suggest a good throttle curve for me to try and solve this problem?
Alternatively could something else be causing the very quick voltage drops? It happens with both batteries so i don't think it is them causing it.

Hope someone can help - Chris.

[moyesboy]

One way to reduce the amp draw wold be a smaller motor pinion. yuo might want to see if you get enugh head speed with a 12T. 11T is the one for a 3550kv, so 12 or 13 is about right for the 3200kv.

If you were pulling a lot of amps then the first thing to overload would be the 25A ESC.
I had a 25A ESC ans when I tried flying with 325 carbon blades rather then 305 woods my 25A esc went into slow shutdown.
On the throttle is a case of finding the number at zero pitch that gives the desired head speed and then going straight line from there to 100% at full throttle.
Try for 2200-2400 rpm as trying to go up near 3000 will probably overload the 25A esc. Any less and the heli doesn't fly nice.

Sadly, another likely reason is that the flightpowers might have seen better days and might be on the way out. more than 100 cycles on those batterys about the life I'm told.

I have some shot lipos and this what they do - fly 2 mins and then the alarm goes off.
The volts drops quite fast to if your alarm is 3.0v per cell, then the packs might be suffering before you can land after the alarm sounds. I have that same alarm set to 3.2v per cell and time my flights to avoid it going off.

[chipbury]

Thanks for that moyesboy.
I did suspect that the packs might be on there way out - maybe i will treat myself to a new one (not neccessarily Flight Power) and see if that helps.
Will using one of the internet head speed calulators work ok for setting the 0 pitch speed? I don't have access to a tacho at present.

[moyesboy]

Its hard without a tac becuase yuo don't know the efficiancy of the setup.
however with the headspeed about right it shoudl lift at 3/4 stick. If it takesmnore than that then headspeedis too low. If it takes less then you have more than 2400. As a rough guesstimate.
Mine hovers at 3/4 stick at 2400 rpm, but needs noticable less stick at 2800 rpm (Quark allows me to switch between two governed head speeds).

[chipbury]

I will do some tests tomorrow (if the weather is good enough).
After a couple of drawings on the back of a beer mat i have come up with a throttle curve to play with (0 28 65 80 100).
Here's hoping for no wind or rain tomorrow!

[chipbury]

I'm using a new battery and have set up a reasonable throttle curve to be going on with and it all seems pretty good.
The LiPo saver is also set at 3.2v per cell now to protect my new battery
Shame i now have to go back to sea for four weeks now which really upsets my flying schedule!