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All data was taken with an AXI 2820/10 outrunner type brushless motor, Jeti 40-3P Brushless ESC (red label) and an APC 10 X 7E prop --- except where noted.

BONNIE flight performance at 3/4 throttle was comfortable. Lower throttle settings produced sluggish performance. So the 2.43 watts/oz factor appears to be about the minimum for this aircraft. The 5.5 volt cut-off point on this Jeti ESC was not attained during this flight. The Bonnie simply wanted to land before that happened.

I must admit that this particular battery pack was brand new and was not subject to very many cycles before this “data” flight was made. As such it is assumed that some amount of increase in flight time might be expected after this pack had been “exercised” somewhat. That might tend to bring it back more in-line with the other NiMH pack and the Ni-CD pack (at 7 or 8 minutes motor run time!).

Recharging this battery at a 2C rate (3.4 amps) took 34 minutes with roughly 1700 mAh going back into the pack. So this pack was totally depleted during the 4:49 flight time.

Weight: 11.7 ounces, Cost - $4.50 per cell (approx. $45.00 assembled in a pack) purchased from Dynamo Electrics Co.

The voltage drop was less with this NiMH pack than it was with either the previous NiMH or Ni-CD packs. As such the BONNIE was able to comfortably fly at 1/2 to 3/4 throttle settings and was able to loop from level flight at 6 minutes into the flight. The pack was warm to slightly hot on landing. Of the three “conventional” battery packs this pack provided the longest motor run. It could also be completely recharged in less than 30 minutes time.

(3) - 8-cell CP-1700 SCR Ni-CD (Sanyo 4/5 Sub-C size cell) purchased from Batteries America.

Weight: 13.8 ounces, Cost $4.25 per cell or roughly $40.00 for a fully assembled pack. This was the least expensive pack of all tested.

BONNIE flew well at 3/4 throttle settings. It started to get more and more “sluggish” when approaching 1/2 throttle. But this Ni-CD battery clearly provided more motor run time than the 8-cell NiMH pack tested first in this data presentation. This pack does weigh more than that NiMH pack (plus 4.0 ounces) but quite honestly that difference was not noted in the BONNIE flight performance. This pack is also a little less expensive than the NiMH pack. The 5.5-volt cut-off point on this Jeti ESC was not attained during his flight. The Bonnie simply wanted to land before that happened.

Recharging this battery at a 3C rate (5.1 amps) took approx. 20 minutes with just about 1700 mAh going back into the pack. Again this pack was totally taken down during the 7:16 flight.

(4) - FMA/Kokam 2 cell, 2 in parallel (2S2P) 2.0 AH capacity (20C load capable) Li-Poly battery pack.

Weight: 10.4 ounces, Cost: not settled as yet but estimated to be around $160.00.

As you can see the BONNIE performance was degraded by the fact that the two Li-Poly cells provided much lower voltage, therefore lower current and wattage. The minimum figure of 2.4 to 2.5 watts/oz. prevailed through most of the flight. This particular battery was the heaviest of the three Li-Poly packs tried because it was made up of a total of four cells. The flight time was more than both the NiMH and the Ni-CD packs, but the performance of the BONNIE was somewhat strained to say the least.

Recharging on an Astro Flight Model 109 charger, set at 4.0 amps, took 1:00 with 3113 mAh going back into the battery. So the battery was not fully depleted during the flight and may have supplied even more motor run time. Also at the end of the flight the voltage had dropped off to 6.6 volts, which is still above the 5.0 to 6.0 volts recommended minimum for a 2 cell (in series) Li-Poly battery.

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(5) - FMA/Kokam 3 cell, (3S1P) 2.0 AH capacity (20C load capable) Li-Poly battery pack.

BONNIE’s flight performance at full throttle (32 amps) was spectacular! It was off the ground in about 15 feet and climbed almost straight up. It drew the attention of everyone at the flying field. The throttle was quickly reduced to below half, and even at that all the regular maneuvers could be performed including loops from level flight.

Keep in mind that at 32 amps motor current the load is at 16C using a battery that is capable of up to 20 C loads!

Recharging on an Astro Flight Model 109 charger, set at 2.0 amps, took 1:17 with 1845 mAh going back into the battery. The battery in this case was not quite fully depleted during the flight. Also at the end of the flight the voltage had dropped off to 8.2 volts, which is still above the 7.5 volts recommended minimum for a 3 cell (in series) Li-Poly battery. The regular (red label) Jeti ESC with a cut off of 5.5 volts would normally be too low a cut-off when using three Li-Poly batteries. But the fact of the matter is that the BONNIE wanted to land, while the voltage had only come down to 8.2 volts. The better way to go in the future is the new Jeti ESC (blue label), which sets the voltage cut-off automatically for the particular battery in use --- a good idea!

(5A) - This same Li-Poly battery pack was tried with an APC 10 X 5E prop, with the idea of reducing motor current to something less than the rather high 32 amps (when using the APC 10 X 7E prop), and yet see if the plane would fly reasonably well. This is the data taken with the same FMA/Kokam 3S1P 2.0 AH (20C load capable) battery and the 10 X 5E APC prop:

Flight Time: 7:23 minutes, mostly at 3/4 throttle settings

@ Full Throttle: 24.7 amps, 10.2 volts, 246 watts, 4.10 watts/oz., 9800 rpm

@ 3/4 Throttle: 18.4 amps, 197 watts, 3.28 watts/oz

@1/2 Throttle: 14.2 amps, 157 watts, 2.62 watts/oz

@ 1/4 Throttle: 7.2 amps, 84 watts, 1.40 watts/oz

The BONNIE flew well at 3/4 throttle settings but at only 6 minutes into the flight it noticeably began to slow down. By 7:23 the flight was over. A subsequent check of the voltage under load, after the flight, showed that the voltage had dropped down to 6.1 volts and was falling fast. This is much lower than the recommended 2.5 volts minimum per cell.

The interesting point here is that when using a 10 X 7E prop at 3/8 throttle I obtained an 11-minute motor run with “peppy” performance. But when I dropped to a 10 X 5E prop, I had to go up to a 3/4 throttle settings and at that rate could only obtain a 7-minute flight time. The higher pitched prop, running at less current, produced the longer motor run time. In retrospect it might have been wiser on my part to reduce the prop diameter to 9 inches, but keep the pitch still at 7! My flying partner, Tom Hunt, suggests that the wing loading of this BONNIE, though pretty light, still might require that the model go faster to fly longer! That’s something to think about!

(6)- FMA/Kokam 3 cell, (3S1P) 2.0 AH capacity (15C load capable) Li-Poly battery pack.

BONNIE’s flight performance once again at full throttle (32 amps) was spectacular! Reducing the throttle immediately to half still provided complete aerobatic flight capability.

The basic differences between this Li-Poly pack and the previous is the load capability, weight of the pack and the cost. This pack is only load capable to 15C, yet the load I impose when at 32 amps motor current is actually 16C.But by reducing the throttle you are down well within the limits of a 15C load. This pack weighs only 6.0 ounces or 2.3 ounces lighter than the 20C load capable pack. And finally this pack can be purchased for $83.50, which is only a little more than you would pay for the recommended NiMH battery (but with almost twice the motor run capability!).

TEST DATA