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Old Dec 15, 2006, 04:53 AM
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Chophop's Avatar
Pleasant Valley Modelport
Joined Sep 2006
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2 Cell Micro Mystery

I see more and more people using 2 cell lipos on their micros and even Esky is selling Honeybee FP's with a 2 cell lipo now. I tried one and could not get much power from the stock main or tail motor. And I read lots of complaints that others have the same problem. I could get PLENTY of power by changing the main motor to an EM350 which is a differently wound RK-370SD-4045 (stock BCP, DF4 etc.). But the DF4 does not have much proportional adjustment and I could not get the tail to spin fast enough. Also, changing to the EM350 brings a need to heatsink the stock Esky/Eflite esc. Not required, but a good idea. I read some people advance the main motor timing for 2 cell.
With my stock motors on 2 cells, I get about 3 minutes of mushy hover, don't even attempt fwd flight. With the EM350, I got 10 minutes of solid hover, and 3 more sort of mushy ones, a good land now indicator. But the tail was too mushy. Maybe 1 more tooth on the tail pinion, but that is a pain.
How are they doing it ?

CH
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Last edited by Chophop; Dec 15, 2006 at 04:59 AM.
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Old Dec 15, 2006, 05:37 AM
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Gino CP's Avatar
Manila, Philippines
Joined Oct 2006
9,564 Posts
People go with 2S lipo simply because they can't use 3S on some systems. One reason is higher voltage is restricted such as in the case of the DF4. Another reason is weight.

I use a 7.4v lipo on my Blade because I have no 8T motor to use with an 11.1v lipo. My 8cell nimh is shot so its the best I have for that heli.
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Old Dec 15, 2006, 12:23 PM
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macr0t0r's Avatar
USA, CA, Fremont
Joined Sep 2004
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Gino pretty much nails it. Some people "settle" for a 2S battery because it's more flight-time than a NiMh but without requiring modifications. For instance, a 3S pack will also work the tail-motors harder and cause them to burn out faster, unless you do the diode-mod or twin-motor mod.

A 3S pack with the proper pinion is definitely more efficient and a better performer. There's a reason whey the competitor helis use 5 and even 6-cell batteries! But, you have to set up your heli properly for it.

- Jim
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Old Dec 15, 2006, 02:33 PM
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swatson144's Avatar
Hampton Roads Va.
Joined Oct 2004
3,560 Posts
Quote:
Originally Posted by macr0t0r
Gino pretty much nails it. Some people "settle" for a 2S battery because it's more flight-time than a NiMh but without requiring modifications. For instance, a 3S pack will also work the tail-motors harder and cause them to burn out faster, unless you do the diode-mod or twin-motor mod.

A 3S pack with the proper pinion is definitely more efficient and a better performer. There's a reason whey the competitor helis use 5 and even 6-cell batteries! But, you have to set up your heli properly for it.

- Jim
That may be your case but I can set my little FPs up to run on anything I want (I have a pretty extensive selection of packs most in pairs) . I use 2S by choice. 1/3 the pack weight makes a nicer heli for me. Proper motor selection and gearing is the key no matter what voltage you elect to run. For the FP 2s is ideal in my opinion because even the H DD motor don't last for long on a 3s so the answer is to add more weight in the back. The normal reason to select a higher voltage is to keep the current down and be able to run a pack that puts the heli in the "sweet spot" AUW, good power, and duration. My favorite micro gets 10 mins on about 1000mAH with hard flight. So I draw 6A average has plenty of power on a RZv2 4200kv with a 12mm feigao on the tail 2x phoenix 10A . Every thing lands pretty much room temp. I could repinion and set up for 3S, and have tried but I like 2S better. I have a HV45 ESC so I could set it up to run 12s if I thought there'd be a reason

Chophop
Too low a gear ratio won't give you enough lift on an FP. up the pinion by a tooth and try again. Pinion changing is a big part of heli life so you might as well get used to it. I have a spread of pinions for all of my helis. It allows me to run different voltages and KV motors to find the "sweet spot" where I like it best. Pinions are probably one of the cheapest modes you can make to a heli. Remember to check for heat often when testing.

Steve
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Old Dec 16, 2006, 02:40 AM
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Joined Jun 2006
296 Posts
You just need a stronger tail motor setup to go with that EM350. I have a dual N30 tail motor setup with 10-tooth pinions on them and it works fantastic on 2-cells. Using a 3-cell pack is the easy way to get lots of power from the main motor and good tail authority, but it will burn your motors out MUCH quicker than a 2-cell pack. Even the main motor doesn't last too long on 3-cells. The stock DF4 4-in-1 can safely run a 3-cell pack if you double-up the main motor FETs and put a small heat sink on them and the 'LD1117' voltage regulator IC.
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