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Old 07-30-2021, 06:28 PM   #1 (permalink)
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Default Li-ion flight packs

li-ion cells that can handle the amps loads we need are starting to arrive. These apparently have been making waves in the vaping community because the manufacturer has rated them for 45A continuous discharge at fairly high temperature (176C is the cutoff). They are also starting to be used by drone racing guys.

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

I was thinking I could make my own 8000mah 6s packs out of these at a very reasonable price. Probably couldn't take hard 3D but maybe they'd be good for sport flying?
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Old 07-30-2021, 07:10 PM   #2 (permalink)
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As you mentioned in the other thread the drone guys flying these shows a lot of promise.

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Old 07-30-2021, 07:18 PM   #3 (permalink)
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looking at the discharge curve, at 30 amps they only give up 1200 mA before hitting 3.5 volts which is what folks like Fromeco say is the stop flying voltage for li-ion packks
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Old 07-30-2021, 07:44 PM   #4 (permalink)
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Quote:
Originally Posted by Thickfog View Post
As you mentioned in the other thread the drone guys flying these shows a lot of promise.

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From what I’ve seen, the drone guys are using them for long range flying. A lot less stressful than FPV racing or likely a harder collective move sport flying.

That said, I’ve been noodling on building a 5S2P pack for my TDSF….
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Old 07-30-2021, 07:49 PM   #5 (permalink)
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Originally Posted by JimJW View Post
From what Ive seen, the drone guys are using them for long range flying. A lot less stressful than FPV racing or likely a harder collective move sport flying.

That said, Ive been noodling on building a 5S2P pack for my TDSF.
Yes! I'm a noodle flyer so all good for me! Lol

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Old 07-30-2021, 08:09 PM   #6 (permalink)
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Thinking about building a 36v pack for my electric bike Almost tripple power with this compare to buying made ones.
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Old 07-30-2021, 10:39 PM   #7 (permalink)
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I was thinking I could make my own 8000mah 6s packs out of these at a very reasonable price.
the best rated Molicel battery cannot supply what the manufacturer do advertise
https://www.e-cigarette-forum.com/bl...ry-tests.7436/

you'll never get 45A continuous so keep dreaming on... even so 6S2P = 45 x 2 = 90A
what heli do you expect to fly with only 90A ?
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Old 07-30-2021, 11:36 PM   #8 (permalink)
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Quote:
Originally Posted by dreamteam View Post
the best rated Molicel battery cannot supply what the manufacturer do advertise
https://www.e-cigarette-forum.com/bl...ry-tests.7436/

you'll never get 45A continuous so keep dreaming on... even so 6S2P = 45 x 2 = 90A
what heli do you expect to fly with only 90A ?

Not even a 700 pulls 90A continuous unless it's a speed heli.

With the sort of flying I do I have flown cheap 25C turnigy packs in a 700 and they would come down barely warm. Now that they have 45C packs available at reasonable prices I don't use those anymore, but for sport flying they worked fine.

I mean I get it, if you constantly bang the collective and never stop flipping the whole flight they won't work for you, but not everyone flies hard 3D.
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Old 07-30-2021, 11:39 PM   #9 (permalink)
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Quote:
Originally Posted by Phaedrus View Post
looking at the discharge curve, at 30 amps they only give up 1200 mA before hitting 3.5 volts which is what folks like Fromeco say is the stop flying voltage for li-ion packks

Maybe an 8S pack or even a 10S instead of 6S?


Regardless li-ion is getting better every year sooner or later they will catch up to lipo. This is because the e-vehicle industry is driving the development. Serious full scale electric airplanes (as in not just a novelty) are even starting to become a thing now. Pilot training schools seem to like them a lot.
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Old 07-31-2021, 10:26 PM   #10 (permalink)
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It would be great to have Li-Ion as an option. I'm sure whatever power was needed could be had by bumping up the cell count as stated. Do Li-Ion batteries require more electronic discharge monitoring? My cordless tool batteries are sure full of circuit boards.
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Old 08-02-2021, 08:22 AM   #11 (permalink)
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Idk, I've flown the Sony VTC 6 cells which are rated at 30a continuous and they don't do very well on a wing using a 2207 drone motor. The motor will pull around 25-30 amps or so full throttle. Even with mixed flying, it'll come down very warm and it has noticeably less power than a lipo due to steep voltage sag.

I run a bigger 6400mah 4s2p pack on my Strix Stratosurfer. It only has a 20a discharge rating but I fly a twin motor setup on it which is very efficient. I still get voltage sag down to 3.7 volts drawing 10-15a cruising. Keep in mind, that 3.7 volts stays there for like 30 minutes of flying as long as you don't hit the throttle too hard. I think the discharge ratings are a bit conservative for Li-Ion packs. Even the "45a" ones. I haven't actually tested those ones mentioned by the OP but I doubt they are any different than a typical "30a" li-ion. Battery mfg's can write whatever they want on a battery it seems.

For a low headspeed helicopter and maybe a 6s3p config, I think you'd be fine. 6s2p would be pushing it though. I would imagine your esc would cut out on even a relatively hard collective punch out.
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Old 08-02-2021, 12:47 PM   #12 (permalink)
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They look like good cells. Possibly an incremental improvement over the Samsung 40T cells we've looked at in the past. I'd have to study the cells myself to make sure Molicel isn't just inflating its numbers for appearance sake. And while I'm familiar with the name Samsung, I don't know Molicel.

I've considered making a 3S or 6S pack of 40T cells as an experiment using one of my 450 or 470 class helicopters. You don't have to hold the helicopter in one hand and LiIon cells in the other too long before it becomes apparent the cells may not easily fit on/in the model. At least not with the canopy on. The morphology of round LiIon and LiPo pouch cells is different enough that some thought may be required to get a LiIon pack to fit.

Still, I'd be a cool experiment.

https://www.18650batterystore.com/products/samsung-40t

Explore by Product ? Molicel
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Old 08-02-2021, 06:42 PM   #13 (permalink)
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Originally Posted by lukeman269 View Post
I haven't actually tested those ones mentioned by the OP but I doubt they are any different than a typical "30a" li-ion. Battery mfg's can write whatever they want on a battery it seems.
Testing shows them to be a bit better than a Samsung 40T for the most part. Initial performance is slightly worse then they pass the 40T and perform slightly better until cutoff voltage. So they are very good cells at a reasonable cost. Samsung recently doubled the price of their 40t cells so I'll be using these to make receiver packs from now on unless some better cell comes along before my current collection of receiver packs starts to fade.

https://budgetlightforum.com/node/66004

Their main claim to fame seems to be that the manufacturer doesn't recommend against e-cig use and has actually said it's fine to use them like that unlike every other manufacturer who have all said "do not use our cells in this way"


EDIT, I wonder if they could make a "long" 21mm cell, like 211500 or something. And how would placing the cathode and anode further apart affect performance of the cell?
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Old 08-02-2021, 07:22 PM   #14 (permalink)
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Quote:
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For a low headspeed helicopter and maybe a 6s3p config, I think you'd be fine.
isn't weight a big factor to you ?

67.8 x 18 = 1220g
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Old 08-03-2021, 05:42 AM   #15 (permalink)
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Quote:
Originally Posted by Atomic Skull View Post
li-ion cells that can handle the amps loads we need are starting to arrive. These apparently have been making waves in the vaping community because the manufacturer has rated them for 45A continuous discharge at fairly high temperature (176C is the cutoff). They are also starting to be used by drone racing guys.

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

I was thinking I could make my own 8000mah 6s packs out of these at a very reasonable price. Probably couldn't take hard 3D but maybe they'd be good for sport flying?
To get to equivalent of 6s 8000mah, I'm assuming you would use 12 cells? Thats $72 and you still have to assemble it.

These: https://www.amazon.com/HRB-50C-100C-...-items&sr=1-50 are $87 or two for $160. Not 8000 but 6000 .. I use them in my 12s specter 700 get like 8 minutes of flight time and I didn't have to assemble anything. Doesn't seem cheaper enough to me.
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Old 08-03-2021, 07:00 AM   #16 (permalink)
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To get to equivalent of 6s 8000mah, I'm assuming you would use 12 cells? Thats $72 and you still have to assemble it.

These: https://www.amazon.com/HRB-50C-100C-...-items&sr=1-50 are $87 or two for $160. Not 8000 but 6000 .. I use them in my 12s specter 700 get like 8 minutes of flight time and I didn't have to assemble anything. Doesn't seem cheaper enough to me.
Those molicel 21700 are rated for 500 cycles when charged to 4.2v, charge li-ion to 4.1v and that increases to thousands of cycles (which is why I always use the "li-ion setting on my charger for my 2S li-ion receiver packs)

imo making your own 2S receiver packs is definitely worth it because most commercially available 2S li-ion receiver packs typicly have less mah than what you can get using Samsung 40t cells, and you have no idea what cells were actually used. (though as I said earlier with the recent price gouging on 40t 21700 cells I'll be using these molicel 21700 they're basically the same but half the cost).


I think li-ion cells will eventually equal or surpass lipo because the e-vehicle industry is dumping a lot of R&D money into li-ion research.
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Old 08-03-2021, 07:30 AM   #17 (permalink)
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Quote:
Originally Posted by fiddle View Post
To get to equivalent of 6s 8000mah, I'm assuming you would use 12 cells? Thats $72 and you still have to assemble it.

These: https://www.amazon.com/HRB-50C-100C-...-items&sr=1-50 are $87 or two for $160. Not 8000 but 6000 .. I use them in my 12s specter 700 get like 8 minutes of flight time and I didn't have to assemble anything. Doesn't seem cheaper enough to me.
Atomic makes some very good points. Not mentioned is that LiIon cells tolerate being stored fully charged very much better than LiPo. After all, these are "Tesla type" batteries and most folks are not going to store their car 50% charged.

I fly a lot of glow models and it is nice to pick up a model any time of the week and know it's 100% ready. In the past I've used LiPo receiver packs and been faced with two choices - either store the model fully charged and suffer puffed packs, or store the model 50% charged and had to stop to charge the model before flying. LiIon has completely eliminated that problem.

I'd be very much interested in see if we could do something similar for flight packs. It'd be pretty cool if all my e-models would be ready to fly by just plugging up the battery.
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Old 08-03-2021, 08:17 AM   #18 (permalink)
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you could always be like the plankers at my flying field. So many swollen packs there as they pay no attention to how they store things. Many of them just store their Lipo packs fully charged (which is why they are all swollen). Every once in a while one will burst into flame while they are charging I assume from all of the abuse. Its quite comical. They are a bunch of old men so you can't tell them anything. I stopped trying to
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Old 08-03-2021, 09:51 AM   #19 (permalink)
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I'd like to try the Molicell batteries but sadly (or luckily) I picked up some 40T cells before the price increase. They were out of stock for a while and when they came back in stock, I added a box to cart.
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Old 08-03-2021, 11:26 AM   #20 (permalink)
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Quote:
Originally Posted by Phaedrus View Post
looking at the discharge curve, at 30 amps they only give up 1200 mA before hitting 3.5 volts which is what folks like Fromeco say is the stop flying voltage for li-ion packks
The only thing I might say to that is that I routinely test LiIon batteries to 2.5 V/Cell.

Admittedly there are issues with discharging to this level. First, the cells typically have moved from something of a linear phase of discharge and are loosing voltage quicker. In the graph below, the red line is voltage for a 2S pack. Notice it begins a steeper decline in voltage at about 3.35V/Cell - but there is still considerable capacity in the pack and the decline in voltage is predictable and not vertical. There is useful energy well below 3.5V/Cell.

Second, much of our hobby equipment doesn't perform its best at both 8.4V and then 5V. I run my glow model helicopters on unregulated 2S LiIon batteries and while the cells may be happy at <3 volts, the servos are not.

The cells themselves don't seem to be harmed by discharging to this level.

So while Fromeco may recommend stop flying at 3.5V/Cell, that may have more to do with insuring adequate voltage to your receiver and servos and less to do with protecting the cells.

Just some things to consider...
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