what battery?

[zev]

I am planing on building the david w tricopter, with dt700 motors, 11x4.7 or 11x4.5 props and probably plush 25amps. the thing I am having trouble with is the battery. I was going to do the turnigy 2200mah 3s 20c, but do you think it would be better to get like a 3300 nanotech? or would the increase i weight make up for the mah difference?

I am not planing on having much weight on it (just a small camera and transmitter, never a gopro) so should I go for an even bigger battry?

thanks!

 

[xibit1987]

http://www.ecalc.ch/xcoptercalc_e.asp

Try do a calculation with this guy. It's really nice and was a very big help to me =)

 

[colorex]

I am planing on building the david w tricopter, with dt700 motors, 11x4.7 or 11x4.5 props and probably plush 25amps. the thing I am having trouble with is the battery. I was going to do the turnigy 2200mah 3s 20c, but do you think it would be better to get like a 3300 nanotech? or would the increase i weight make up for the mah difference?

I am not planing on having much weight on it (just a small camera and transmitter, never a gopro) so should I go for an even bigger battry?

thanks!

From my experience:

Don't get the 20C 2200mAh 3S. It's got too low discharge capacity. I run a 25C battery on my tricopter (with even smaller props) and it puffs the battery when flying moderately fast!

I would rather recommend using nanotechs - any number between 2200mAh and 3300mAh should be fine with those props. Just make sure you got at least 30C if you choose a 2200mAh.

 

[Cyberdactyl]

I'm using those Turnigy 2200 3S 25C for my 1,260gram quad, including battery. Getting about 10 minutes messing around in my backyard, and maybe climbing to around 150 ft a few times. The standard poor man's fare of DT750's and HK 20A ESC 3A with two 3/16" lightweight plywood plates with four 18" 1/2" x 1/2" poplar sticks.

 

[zev]

xibit1987: I have tried that. it says my setup (with 3300 nanotech and 12x3.8props) will fly for 14.61min. I don't know how trustable it is though, because when I enter in the tricopter 2.6 specs it says it will get 9.22min of flying but I know it will do 12-15mins.

colorex: I thought I read somewhere that a lower C rating made for longer (if less exciting) flight times. must do more research!

Cyberdactyl: so jealous of the DX8 in the corner . what props are those? I am always interested in others setups/flight times.

 

[Ak Flyer]

colorex: I thought I read somewhere that a lower C rating made for longer (if less exciting) flight times. must do more research!

The C rating is the rate at which the battery can discharge safely. The actual draw depends on the load you place on the battery.

If you place a tiny motor and prop on a low C battery it will run for a really long time. Same motor and prop on a High C battery and it will run a really long time.

If you place a huge motor and prop on a high C battery it will run for a while at max load and all is well.

If you place that huge motor and prop on a low C battery, it's going to ask for more than the battery can safely provide and it will damage (puff) the battery.

If you aren't asking for a high discharge rate, (glider, transmitter, trainer) then you don't need a high C rating. If you are placing large amp draws on a battery (helicopter, quad, tri, 3D, plane, EDF jet) then you must run a higher C rated battery to safely provide the higher amperage draw.

Hope that makes sense.

Here's an example.

My super cub ran great with the stock brushed motor on the stock 3S 1300 15 C battery. I upgraded it to a Turnigy Park 480 brushless setup. I tried running it on the stock battery at first and it would spin the prop up real fast and then throttle back. The battery simply couldn't provide the amperage to give me full speed. I threw in a 3S 2200 30C from my helicopter and it would not only reach full speed, but hold it for fifteen minutes.

The capacity (mah) of the battery doesn't impact this. The capacity will simply determine how many amps you have available. Your discharge rate determines how fast you can safely use it up. You will never go wrong with a higher C rated battery, but you will pay more for each battery because of it.

 

[zev]

Ak Flyer: ok, I think I get that. so I suppose if your motors are small enough, a lower c battery would be just as good, but cheaper and lighter, and therefore better.

 

[Cyberdactyl]

Cyberdactyl: what props are those? I am always interested in others setups/flight times.

The ones you see are 10x45. They are pretty darn durable. If you notice in the pic above, the rear prop (in the lower right) has a bit of fatigue stress discoloration at the root from a previous hard landing. I was tempted to change it, but examined it closely and it appears ok. They only come with an insert for one side of the prop. Since I use a small washer on both sides, it's ok.

I would really steer away from three bladed props. From my experience, they tend to magnify instability when descending into down wash and any P & I tuning issues I had seemed to be more pronounced. However I DID like that these have the insert for both the top and bottom.

 

[xibit1987]

About the 3 bladed prop http://www.youtube.com/watch?feature=player_detailpage&v=Cm8Mxqwttnc#t=223s

 

[colorex]

these

Unfortunately these seem to have suffered the Backorder Death - and are probably replaced by these:

http://www.hobbyking.com/hobbyking/...y=&sortBy=Relevant&NumPerPage=20&currentPage=