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Author Topic: Li-ion 2S, 3S and 4S potential applications  (Read 1149 times)

Offline Brent Williams

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Li-ion 2S, 3S and 4S potential applications
« on: November 28, 2022, 04:08:45 PM »
My other post on this topic seems to be non functioning, so I am reposting.

The electric CL stunt hobby has gravitated towards higher battery cell count setups for many good reasons. Capacity, weight, prop selection, and perhaps overall drive, ect.

The new developments in powerful li-ion packs have presented some interesting opportunities to revisit large capacity 3s and 4s options.  The goal of this thought experiment is to look at lower cost, high capacity systems to ease the transition to electric flying.

As an experiment, I am contemplating building a 3s4200 li-ion pack based around the Molicel P42a.
The P42a is rated for 45 amp continuous discharge and has 4200mah of capacity.
The individual cells weigh 68g each, so the complete 3s/4200 pack should come out around 220g (7.75oz or so).

Doing the math, there is enough mAh capacity that you could potentially use this pack with a complete airplane weight up to the mid 50+oz range.

There is the question of diminishing returns, as the 3s setup takes more amps to run, so the ESC and wire must follow suit.

A 4s4200 li-ion pack built from these same cells would probably weigh around 290g/10.2oz and should have plenty of capacity for a 65oz+ plane. 

Thinking primarily of guys using the simple governor/fixed rpm timers, but there isn't any reason that this wouldn't also work with active systems.
« Last Edit: December 13, 2022, 02:53:38 PM by Brent Williams »
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Offline Brent Williams

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Re: Li-ion 3S and 4S potential applications
« Reply #1 on: November 28, 2022, 04:26:09 PM »
The 3s and 4s li-ion packs are pretty simple to visualize.  I will attach some 3s and 4s wiring diagrams for examples.

The P42a cells are each 21.5 x 70mm (.846" x 2.75"), so the packs are quite compact. Complete 3s and 4s packs would be around 1.75" x 3".
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Offline Brent Williams

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Re: Li-ion 3S and 4S potential applications
« Reply #2 on: November 28, 2022, 04:39:02 PM »
Wiring diagrams.
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
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Offline Dennis Adamisin

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Re: Li-ion 3S and 4S potential applications
« Reply #3 on: November 29, 2022, 08:21:12 AM »
Hi Brent

My first electric stunter used 3S.  Moved on to 4S but with many more packs & motors available now I recently started dabbling in 3S applications again as a weight save on Classic sized stunters.  I found some 3Sx3500 LiPo's that weigh 7.5 oz and have used them on up to a 52 oz airplane so far - and have not hit their limits.  BTW, I am charging these like Li-Ions, charging to 4.1V instead of 4.2V and they are working great.  Thus, I completely support your assertion that the 3Sx4200 Li-Ion could be the ticket for maybe up to 60 oz or so. 

I am also using 4Sx3500 LiPos on an SV-11 (70 oz RTF); your 4Sx4200 LI-Ion would add 20% capacity at similar weight, not bad at all!


Addendum:
I have a couple 3Sx4500 Lipos that weigh weigh 10.7 oz, and are 1" x 1.7" x 5.3" (25mm x 43.5mm x 135mm.  For comparison that is 3.2 oz heavier and nearly twice as long as Brent's Li-Ions.
« Last Edit: November 30, 2022, 11:12:56 PM by Dennis Adamisin »
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Offline Brent Williams

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Re: Li-ion 2S, 3S and 4S potential applications
« Reply #4 on: December 13, 2022, 02:32:51 PM »
Dennis Adamisin and I have had some very interesting chats regarding some potential uses for 2-cell 4200mah Li-ion packs.  With an appropriately high KV motor, like 1800-2000Kv, a 2s4200 pack could make a really neat, lightweight combo for airplanes around 24-32 oz range -ish.  ie, all those Ringmaster, Flite Streak, Skyray, Corehouse streak RST, Shoestring, ect. sized planes.  Dennis mentioned that this could allow him to: (1.) lose nose and tail weight to arrive around a 24oz goal weight for his Ringmaster, (2.)to spin a 9x6 type prop, and, (3.)it should not tax that large capacity 2s/4200mah battery too hard in the process.  Sounds pretty compelling to me!

The Tempest 2217/1950kv, a 9x6 or cut down 10x6 and a Talon 35 esc seem like a pretty good package for the 2S experiment.  Running that 2217/1950kv Tempest motor at 7.4v at 75% or so would still allow 10.8k on paper.  Should have plenty of headroom.  That Tempest 2217 motor lists 340w max @ 2S, which should be more than plenty for a 24-28oz flying weight. 
If more a more powerful motor is needed for larger or heavier airplanes in the 29-33oz range, the BadAss 2320-1860Kv (3.26 oz.) boasts 407watts on 2 cells for a weight gain of only .7oz.

The weight for that 2217 combo should be around 9oz, minus prop and spinner.
- 2s/4200 Li-ion battery: 5.4oz (estimated)
- Tempest 2217-1950Kv: 2.54oz
- Talon 35 Esc: 1oz

https://innov8tivedesigns.com/tempest-2217-1950kv-brushless-motor.html

https://innov8tivedesigns.com/badass-2320-1860kv-brushless-motor.html

(With as deep as you can take Molicel P42a 4200's into the discharge curve, I think that you potentially could use one of these packs clear up to around 40oz.  On paper it works out.  Actual results on the plane are yet to be determined.)
« Last Edit: December 14, 2022, 12:11:46 PM by Brent Williams »
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Online Steve Berry

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Re: Li-ion 2S, 3S and 4S potential applications
« Reply #5 on: December 23, 2022, 09:20:41 AM »
To make sure I'm understanding this correctly, I could conceivably combine this battery:

https://www.18650batterystore.com/products/molicel-p42a

and this battery holder:

https://www.amazon.com/ZRM-Battery-Holder-Storage-Container/dp/B09XV41V71/ref=sr_1_3?crid=3FDYBBPDHJIG1&keywords=21700+battery+pack&qid=1671812106&sprefix=21700+battery+%2Caps%2C85&sr=8-3

to make a simple 2S pack, semi-permanently mounted on the plane, and just switch out the batteries like changing AA batteries? Just mount and hardwire everything, and it should be good to go?

Steve

edit: did a little more searching and found these in both 3S and 2S configurations, which I'm guessing would work very well, too, albeit for more of a "normal" battery pack to be welded/soldered, wired, & wrapped:

https://www.amazon.com/ZRM-Battery-Shockproof-Brackets-Batteries/dp/B08G1126WH/ref=sr_1_3?content-id=amzn1.sym.8fc539a0-3d8d-48b5-992f-26aed91324e7%3Aamzn1.sym.8fc539a0-3d8d-48b5-992f-26aed91324e7&keywords=21700%2Bbattery%2Bholder&pd_rd_r=0e8e765a-85a6-4f76-b4b5-822fd31e5018&pd_rd_w=tlsLU&pd_rd_wg=8jbY7&pf_rd_p=8fc539a0-3d8d-48b5-992f-26aed91324e7&pf_rd_r=5EXQVRJ3VWW47Z08T67V&qid=1671812723&sr=8-3&th=1
« Last Edit: December 23, 2022, 10:02:25 AM by Steve Berry »

Online Ken Culbertson

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Re: Li-ion 2S, 3S and 4S potential applications
« Reply #6 on: December 23, 2022, 12:02:38 PM »
To make sure I'm understanding this correctly, I could conceivably combine this battery:

https://www.18650batterystore.com/products/molicel-p42a

and this battery holder:

https://www.amazon.com/ZRM-Battery-Holder-Storage-Container/dp/B09XV41V71/ref=sr_1_3?crid=3FDYBBPDHJIG1&keywords=21700+battery+pack&qid=1671812106&sprefix=21700+battery+%2Caps%2C85&sr=8-3
This holds posibilities.  Imagine just opening a hatch and dropping out the cells and sliding new ones in.  Where the "gotcha" is in the connections.  Not sure they would be solid enough to take the high draw.  I think I like the pack better on a 6s PA setup but the cell sizes sure do open up shape options.  For the smaller ones, I love the holder idea for a 2-3s.

Ken
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