Author Topic: Swapping a 3 cell for a 4 cell (update) (Read 1964 times)

Dwayne · « **on:** June 30, 2014, 05:37:26 AM »

Hey all. I've been flying a plane similar to a Twister-RD 1 with a E-Flite 15, 12/6EP and a 3000ma 4 cell at 8800 rpm. Runs great but I was wondering what size or if a 3 cell would work and would I save some wieght?
Thanks

Russell Bond · « **Reply #1 on:** June 30, 2014, 06:45:36 AM »

No, with a 3 cell your ESC will be operating at over 90% so you won't have enough "headroom".

Tim Wescott · « **Reply #2 on:** June 30, 2014, 09:22:32 AM »

And if you did jigger around motor, prop, and ESC to match 3 cells, you'd need a 4000mAh pack, which would weigh roughly as much as a 4S 3000mAh pack. If anything you'd add weight to the system because you'd need bigger wires and a bigger ESC.

You need a certain number of joules to perform the pattern, and LiPo batteries more or less weigh the same amount per joule.

55chevr · « **Reply #3 on:** June 30, 2014, 09:56:15 AM »

If it is working the way it is --- leave it alone ... "If it ain't broke, don't fix it." (my Dad's often repeated statement)

Dwayne · « **Reply #4 on:** June 30, 2014, 11:11:36 AM »

Thanks guys. 55, always looking for a way to shave a few grams.

Dean Pappas · « **Reply #5 on:** July 02, 2014, 09:31:23 PM »

Hello Dwayne,
So the real question is, how much battery capacity do you consume each flight?
How much does your charger say it put back into the battery?
Maybe there is weight to be saved with a smaller capacity battery, maybe not.
How much does the battery you use now weigh?

Regards,
Dean

Keith Renecle · « **Reply #6 on:** July 02, 2014, 11:48:55 PM »

Hi Dwayne,

Most .40 size profiles are flown with motors like the E-Flite 15 with the APC 11 x 5,5 E prop and a 4 cell 2200 to 2650 mAh lipo. The rpm is set to around 9800 to 10200 depending on where you are flying. The 12 x 6 does give huge thrust but is maybe a little big for that size stunter. The turn rate is great with the 11 x 5,5 and you can also get the pusher version as well. My Eze-Pro stunter is similar to your model and many have been built that are flying at an all-up weight of 42 to 43 oz. At sea level the 2200 battery just makes a complete pattern, but only just so the next size up is a little better.

Keith R

Dwayne · « **Reply #7 on:** July 03, 2014, 06:09:18 PM »

Quote from: Keith Renecle on July 02, 2014, 11:48:55 PM

Hi Dwayne,

Most .40 size profiles are flown with motors like the E-Flite 15 with the APC 11 x 5,5 E prop and a 4 cell 2200 to 2650 mAh lipo. The rpm is set to around 9800 to 10200 depending on where you are flying. The 12 x 6 does give huge thrust but is maybe a little big for that size stunter. The turn rate is great with the 11 x 5,5 and you can also get the pusher version as well. My Eze-Pro stunter is similar to your model and many have been built that are flying at an all-up weight of 42 to 43 oz. At sea level the 2200 battery just makes a complete pattern, but only just so the next size up is a little better.

Keith R

I've read about this before. I tried a 11/5EP 9,800 rpm first but I only got 4 1/2 minutes on the same battery. Then started playing with different props that I have on hand (I fly R/C as well) and hit on the 12/6 at 8,800. By what you are saying and what I've read the 11/5.5 should work, maybe there is something wrong with my set up.

Pheonix 45
Hubin FM 2

Dane Martin · « **Reply #8 on:** July 03, 2014, 11:37:06 PM »

hopefully i didn't miss you saying this already, but have you tested the battery's capacity? i mean, if it's a battery you use on an RC and it's slowly slipping away, you wouldn't really notice the power/capacity loss until you had a new project where it was more important?
just as an idea....

Dwayne · « **Reply #9 on:** July 04, 2014, 09:51:08 AM »

Very windy today but managed two flights. The 12/6 does not like wind, my plane slowed noticeably heading into the wind. I'm only putting back in 2005 ma so there is room, I will try the 11/5.5 again and see what happens. Will post the results.
Thank again.

Keith Renecle · « **Reply #10 on:** July 04, 2014, 11:07:50 AM »

Quote from: Dwayne Donnelly on July 04, 2014, 09:51:08 AM

Very windy today but managed two flights. The 12/6 does not like wind, my plane slowed noticeably heading into the wind. I'm only putting back in 2005 ma so there is room, I will try the 11/5.5 again and see what happens. Will post the results.
Thank again.

That will be interesting Dwayne. The 12 x 6 diameter will slow you down a bit in the wind, and that battery should have plenty of power on the 11 x 5.5 so let us know. Like I said, the 27\650 4 cell should be about right and a lot lighter as well.

keith R

Author Topic: Swapping a 3 cell for a 4 cell (update) (Read 1964 times)

Dwayne

Swapping a 3 cell for a 4 cell (update)

Russell Bond

Re: Swapping a 3 cell for a 4 cell

Tim Wescott

Re: Swapping a 3 cell for a 4 cell

55chevr

Re: Swapping a 3 cell for a 4 cell

Dwayne

Re: Swapping a 3 cell for a 4 cell

Dean Pappas

Re: Swapping a 3 cell for a 4 cell

Keith Renecle

Re: Swapping a 3 cell for a 4 cell

Dwayne

Re: Swapping a 3 cell for a 4 cell

Dane Martin

Re: Swapping a 3 cell for a 4 cell

Dwayne

Re: Swapping a 3 cell for a 4 cell (update)

Keith Renecle

Re: Swapping a 3 cell for a 4 cell (update)