View Full Version : CP Pro sucking mega juice???
10-24-2006, 10:56 PM
I have a CP Pro converted to brushless. 3800kv helidirect motor and sonix 18A esc. I have found on the stock battery, it is taking 89-100 mah/minute of flight out of the battery.
Does this seem high? I figure I can fly a max of 7 minutes and be right at the 80% rule.
If I got a higher C rated pack, would that improve efficiency and flight time? If you have the E-flite set up, please let me know how it compares.
10-25-2006, 11:47 AM
I fly an E-flight Park 370 3600kV BL motor with an 8T pinion and 1320 mah battery. I get a good 20 minutes out of each charge.
What size pinion are you running? What's the mah capacity of the battery? Appears to be 900 mah based on your 7 mins/100 mah/min pull.
Check for tight gear mesh, binding in the head etc... You should be getting a few more minutes out of that setup...
10-25-2006, 12:28 PM
I agree with Skiddz...
I am flying the pro around with a 700mAh 3S-pack, all stock, and I get pretty exact 11mins out of that until the battery voltage drops below 9V (got a LED for that which comes on if the voltage is below that value).
Now I even carry extra-weight in form of a fuselage around, and still I have 10mins left...
So either something's wrong that's using extra-power like binding, too tight gear mesh, etc, or the battery has not really that capacity that's written on...
Did you also check your RPM? If that is too low, you'll need extra torque, which equals in extra current, meaning shorter flight-time...
Making the calculation on the battery load, if you empty your battery in 7 minutes, you'll have a load of approximately 9C on the battery, which should be in the green for any kind of battery nowadays available. So using a battery with higher rating would not really solve the problem, only using higher capacity would let you fly longer.
A higher rating only ensures that the voltage isn't dropping under load, which - in my personal and honest opinion - should not be the issue at 9C at all.
Which brings us back to Skiddz conclusion: Either something's not right in the power-train, or the battery might be at the end of its life.
10-25-2006, 03:44 PM
That doesn't seem too far off to me. I am running a brushless 370 4100 kv motor in a Blade Pro. I get around 8 mins of flight and put back in a little over 600mah each charge with the stock 800mah lipo. Mine is a little heavy though with an Align cold string kit for night flying... but not a huge difference from stock weight. When I check my batteries after a flight they are not below 11 volts (no load). I always try to pull the same mah from my batteries staying around 80%. There are many who run them longer and let the voltage drop farther, but my 2 800mah batteries have been through almost 70 cycles each now and have not degraded at all in performance. They still use the same mah/voltage they did when they were brand new. Removing ~600mah always leaves them around 11.1 volts.
I am sure I could run them a little longer, but after killing 2 batteries in my rex after only 40-50 flights I started using the method above. I have had the same resluts for the larger Rex batteries too. 2 Align 2100 packs are a little over 80 flights with exact same voltage/mah readings I got when they were new.
I'm not saying this is something anybody should follow. There are many who disagree and say that mah doesn't mean anything and its only voltage that matters. Either way, this method has worked great for me so I am sticking to it. If I want more flight time, I'll just put in another battery :D
10-25-2006, 07:40 PM
Thanks for the replies guys.
I have a 9t pinion set on the 3800kv motor. I am using the symetrical blades stock woodies, dual tail motor set up, and super skids. I guess the added weight could be costing me some efficiency. I am also using the stock 800 mah lipo.
10-26-2006, 01:56 AM
the optimal setup is 1320 mAh batts 3600 KV motor with 8 tooth pinion . I get 15 - 20 min with this . if your using higher KV's like 3800 - 4100 these motors are faster and so you need to gear them down more , the 4100 is way overkill , you would need like a 6 tooth or somthing to get the right headspeed , so you probably running your motor way below its optimum efficiency .
10-26-2006, 04:07 AM
bpd282, if you have the 3800kV motor, then you definitely need the 8-teeth-pinion...
If you rig the 3800kV for the correct head-speed, you will operate it below its best efficiency, at too low RPM, which draws more current...
Which will also heat up the motor more than it would at best efficiency.
And as well, eflite has putten a maximum RPM on the stock head (2100RPM, if I remember right), if you go above, you might get binding...
Get ahold of a 8t-pinion, that will help a lot... :)
10-26-2006, 12:31 PM
the 4100 is way overkill , you would need like a 6 tooth or somthing to get the right headspeed , so you probably running your motor way below its optimum efficiency .
The E-Flite Brushless 370 4100 kv motor is the exact motor from the Pro's manual reccomended for upgrading the Blade Pro to a Brushless setup. I run it with an 8 tooth pinion and E-Flite 20 amp speed control which are also from the reccomendations in the manual. I think the low (fixed) timimg of the E-Flite speed control makes it more tame. I run a flat 100% throttle curve in Idle up and haven't had any binding issues with the stock head. Although, I have heard of people getting too much head speed form the 4100 kv motor when using other speed controllers besides the E-Flite.
How do you run those 1320 batteries??? My blade runs great with the 800 but is noticably more sluggish with just apex 1100s. There are lots of people running those 1320s, but I wouldn't want to fly them. I like my heli very nimble and the Blade seems very sensitive to weight changes... although the long flight time sounds good. How much do those weigh?
10-26-2006, 11:46 PM
I've flattened out my pitch curve quite a bit and let the motor run as fast as possible at all times. I run an 8T pinion. I also have a CNC frame, DD tail, alum swash. I did the head setup with digital calipers and made sure everything was as close to perfect as I can get it with these plastic parts. My gear mesh is bordering on the sloppy side as well.
I don't use the stock Tx anymore. I set up my CP on my 9C a long time ago and I'm able to tweak throttle and pitch curves to my liking. Check out the thread by Rebuild that has to do with the CP and a computer radio. I posted all my settings there.
E-flite told me several months ago to shoot for about 2100 RPM head speed.. The 4100kv motor and an 8T pinion will get you right around that without messing too much with the pitch. I get a little over 2000 RPM with my 3600kv motor and a Thunderbird 18 ESC.