jimcork1

My Feedback: (4)

I have a speed 400 on a zaggi. I have also acquired a 3s 700 ma Lipoly pack and charger. I have a Jetti controller but it is not one that is jumperable for Lipoly. Which controller should I use if I continue using the speed 400 motor. I realize this is not brushless, I am not trying to max power the zaggi,, but only to get it back in the air after Katrina.


So to use the lipoly pack,, brushed speed 400 which is the right controller that will working in this application. Thanks vettdvr

jdetray

You can use your Jeti ESC. You just need to keep your flights short at first, then check the lipo voltage upon landing to be sure the lipo is not being over-discharged. As long as you time your flights so as not to over-discharge the lipo, you don't need a lipo-compatible ESC.

Another consideration is the advisability of using a 3S lipo with that motor. The motor may not last long with such a high voltage. You'll have good performance, though! Reducing the prop size from what is normally recommended will help the motor deal with the high voltage of the 3S lipo.

- Jeff

jimcork1

My Feedback: (4)

Jeff I have cut the prop down and this has worked well. The lipoly 's are a test pack for me. I tried using the jetti, but can't figure out what's going on with the speed control. I retart the throttle and wait then push up the throttle and the motor will begin to run but only briefly. Then it will stop as the throttle is advanced further forward. I have reversed the throttle and it won't work at all. Anythoughts. Thanks vettdvr

Leo L

I presume that when you shut everything down and start all over again, the same thing happens. The most likely problem is that you are exceeding the amperage rating of the ESC and the ESC is shutting you down. If you want to fly with this motor/battery/prop combo, you need to increase the size of the ESC.

jdetray

I agree with Leo. It's either that or the ESC has its LVC set so high that it is tripped as the current goes up when you advance the throttle.

- Jeff

jimcork1

My Feedback: (4)

Ok, still learning,, I thought the motor load determined the amperage not the battery. The motor prop is the same I used with a 9.6 nimh 700 pack. It did not over current on the nimh and worked well. Lost the nimh pack in katrina. The voltage on the lipoly is right at 12 v full charge. The sbc is rated for 12 v. max so the lipoly is right at the max for the sbc.

If I use only 2 lipoly cells the voltage won't be but approx 7 and won't turn the speed 400 motor well enough. So I am still puzzled what to do? I don't have a 9.6 nimh or nicad to try except for what's in the transmitter.

I looked at the new jetti sbc's rated the same as mine and the new ones have a lipoly setting. Mine does not appear to have this voltage range setable.

jdetray

Jim -

Your understanding is basically correct. Sorry if I confused you.

A given motor and prop will try to draw a certain amount of current. However, if the battery is not capable of supplying that much current, the battery voltage may drop so low that the ESC cuts off power to the motor. That's the function of the low-voltage cutoff feature in an ESC -- it protects the battery from being over-discharged. If that is what's happening, you need a better battery.

It would be helpful if you knew what the LVC voltage of the ESC is. Since the ESC is not designed for lipos, it might be setting the LVC so high that even a small drop in voltage triggers the cutoff. A battery's voltage will always drop under load.

A second possibility is that the current is greater than the ESC can handle, in which case the ESC may be shutting down to protect itself. In that case the solution is a bigger ESC.

The best way to determine what is going on is to hook the power system to a wattmeter so you can observe the current and voltage under load.

- Jeff

jimcork1

My Feedback: (4)

Jeff, what you said now makes sense. If the lipoly isn't large enough the volt drops and the sbc cuts off the power to the motor.?

What I have is a 700ma 3S lipoly that has over 11 volts at full charge. What I really don't know is how much the voltage drops when power is applied and/or how much amps are being pulled. So what you stated does seem logical. thanks jim

jdetray

Jim -

If your 3S lipo is only "over 11 volts at full charge" that could be the problem right there.

A 3S lipo at full charge should measure 12.6V. Full charge for any lipo is 4.2V per cell.

If your "fully charged" lipo is much less than 12.6V, there is a problem with either the battery or with your lipo charger.

On the other point, yes, if a battery is too small for the job, its voltage may drop so much that the ESC cuts off the motor.

- Jeff