Anything R/C

Hey you pros,
got some stupid questions here...yeah yeah I know, there are no stupid questions but just stupid people asking questions...

So I am mostly a zagi flyer, but I have a few other park flyers, and helicopters too.
I recently upgraded the motor of my zagi to a multiplex permax 400BB motor. I am using the wattage 380 speed control with 30 amps capability. I tried to get more power out of it so I made some 10 cells nimh 1100mah batteries. But it seems like the stock zagi 8 cells 1700mah nicad has much more power than the 10 cells. So i hooked up a meter to check the voltage of the motor in full throtle and compared both batteries. It turns out that the 8cell nicad 1700 gives a higher voltage at the motor than the 10 cells 1100 nimh. The voltages are 6.5V, and 5.6 V respectively. How come the 10 cellss has less power? Also I did the same comparison with the stock setup which is the 20 amp zagi esc, and the stock 6V 400 zagi motor. The results are the same, the 8 cells voltage at the motor is higher than the 10 cells. The stranger part is that the stock setup has a higher voltage than the new motor setup. It is 8.6V for the 8 cell and 7.4V for the 10 cells respectively. So how come a motor thats rated at 6V has a higher voltage during full throtle, than a tuned 400 motor rated at 7.2V with ballbearings?

I knew I should have paid attention in my power engineering class when I was still in school.

davidfee

Basically what you are observing is the result of internal resistance. The smaller 1100mAh cells have a much higher internal resistance than the larger 1700mAh cells. Therefore, the voltage under load will drop more with the small cells. If you specify which types of cells they are, we could get more specific.

-David

Peter Khor

My Feedback: (4)

fwiw as a point of comparison, I am using 10 cell KAN950 pack on a S400 Long Can and 5.5x4.5 APC prop - it pulls +15A and pack voltage is just shy of 10V. As David mentioned, there are couple of difference 1100 2/3A (I presume that's the size you have) out there, the generic ones (BatterySpace/BYD) won't give you any performance at high current drain - stick with known cells like KAN and CBP's if going for 2/3A's (imo HECells have been left behind).

Matt Kirsch

My Feedback: (21)

The reason the voltage is higher with the stock 400 is because it is not putting as much load on the battery. Your Permax is a much "hotter" motor, meaning it is wound to spin faster than the stock 400 on a given voltage.

Are you running the same size prop on the Permax as you were on the stock 400? I ask because the voltages you measured for the Permax are alarmingly low. You're putting way too much load on those batteries, which indicates to me that you're running too large of a propeller.

Anything R/C

well I am using the 2/3a size cells at 1100mah nimh. and also, to the other question, I am using a prop thats has a similar length but the pitch is less than the zagi, the new prop is 5.25x4.75. So what can I do to get full power from this battery and motor setup? The 8 cell with the new motor, even though the voltage seems low, but power is reasonable. but the 10 cell has no power at all compare to the 8 cell nicad...

Peter Khor

My Feedback: (4)

You still haven't mentioned which 2/3A cells you're using? (Brand? Where you got them from?)

Anything R/C

well i don't know the brand I got it from batteryspace.com. It said china on the cells.

Ronnies

Keep in mind that planes and cars are going to draw much higher amps then what store bought AA batteries were designed for

Matt Kirsch

My Feedback: (21)

Not all 2/3A cells are created equal. Known good brands of 2/3A cells are KAN, CBP (cheapbatterypacks.com), Sanyo, and HECell.

From your description of the performance of these cells, they're substandard low-quality Chinese cells. Cheaper is not always better

KAN1050 cells are very affordable, and the best ones on the market right now. Replace your China pack with KAN1050s and your plane will come alive.

Anything R/C

so what's up with the prop issue? You were saying the prop is too big??? Please help....

Anything R/C

So is there anything I can do to help with the power with the new motor other than changing batteries? Prop size is about the same as stock. Even with the stock zagi 1700 battery it gets really hot?

Ronnies

then only thing I have found out about props with small 400 motors is that anything above a 6x4 is to big those speeed 400s like 5x4.5 size props electric only.