A smaller Li-ion cell for 1/2a and 3696

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Lee Liddle
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Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

A smaller Li-ion cell for 1/2a and 3696

Post by Lee Liddle »

Image

This is the Konion cell made by Sony. There are supposed to be three versions. The 1200mah, the 1600mah (picture), and a 2600mah.
This cell in 11/16"in dia and 2.5" long.It weighs 43g (aprox 1.5oz). It is a long thin cell which does not lend itself to high charge/discharge rates. It is supposed to be a 12C discharge and a 2c charge. So far I find it to be "happy" at about 15a discharge which is about 10c. I was expecting 18a (12c), but 10c will give good long flights.

It comes from the Makita 18v 3ah battery pack. There are 10 cells setup in a 5s2p arrangement. Cost is $99 off the shelf at Home depot (about $60 on Ebay). So the cost per cell is $10 ($6).

Since the big outrunners that many are running in 3696 draw about 16a, I thought that this might be the perfect match for 3696. However these cells seem to get too hot, and their voltage dropps too much at 16a. I did not give them any break-in time and got the first pack pretty hot, so I may have reduced it`s ability somewhat.

There was not as much info out there on this cell, so it was a little trial and error. In fact there was some incorrect info which caused me some probs at first.

A post on RC groups says that these are to be charged to the same 3.6 max as the M1 cells, but that`s wrong. These are 4.1 or 4.2v cells and can easily be charged on a regular LiPo charger.

I charge my "test dummy" pack at 2a now, and the last time it took about 1550mah. For a while I thought that I had a 1200mah pack, but now I see that they are 1600`s.


A 3s pack weighs about 5,25oz which is a little less than the 2000mah commonsense batts.

The only draw back is the lower (13a) discharge ability. This can be overcome by using a 20mm innrunner motor on a gearbox. Cash is using one and is only drawing 13a at 9k. I have had similar numbers in some bench tests.


Like the M1s, the main advantages of these cells is safety (charging and impact), faster charging(2x as fast for these cells) and longer life (up to 10x longer)

Cajun, these may be the 3696 cells that you are looking for, but you will have to run a more efficent motor than the 2809.
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

My thoughts for the care and feeding of these cells:

Unlike the M1s these cells need to be broken in for several cycles to begin with. Charge/discharge rates of 1c/4c (1.6a/6.4a) for several cycles should do the job. After that 2c/9c (3a/14a) I`m pretty sure are safe. Higher rates may be possible, I need more testing.


These cells will work in smaller models where m1s are just too big.
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

My thoughts for the use of these cells:

1/2a...APC 5.7/3 at 18k...I know that 3 cell will work on a 20mm motor with a 3300kz. But a 5oz pack is a little heavy. A 2spack might work with the right motor and gearbox, but then you add the weight of the gearbox. With the direct drive 3300kv motor the weight is between 8 and 9oz for the motor/prop/esc/batt combo. That leaves 9 or 10 oz for the airframe if the min weight is 18oz.

3696.... MA9/6 at 9k...... A 3spack gives about 11v at 13-14 amps. That equals about 150w. The 2908 motor need about 190w to do the job. So a more effecient motor will have to be found. That most likely means a 20mm inrunner with a gearbox, because there are no 20mm motors with 4mm or 5mm shafts that I know of. As I said above, Cash has a good combo working at 11v and 13a, so this would be a good batt for that.

SSC,,,,MA8/3 at 17.5k..... Here you are limited by the amp draw limitations of the batt (aprox 13-14). What should work is a 4s2p batt. This would be two 4s packs hooked in parallel. This would give about 14v and 27a for a total of about 340w. Each 4s pack weighs 6oz, for a total weight of 12oz. The 3s2plipos that I have used weigh 11oz so there is only a small weight penelty.
That`s enough power to do the work. It should take an inrunner direct drive of about 1800kv to hit the rpm limit, or a higher kv motor on a gearbox. There are quite a few 28mm inrunners out there for less than $65. Only a few with direct drive numbers and those all have 3.17mm shafts or smaller, so theyhave to be used as a pusher. With a strong gearbox, tractor designs will be open for use.
Rabbit Leader
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Joined: Thu Mar 15, 2001 11:37 pm

Post by Rabbit Leader »

Lee, i think that the gearbox combo is running closer to 14.5 or so, not real sure. JP remembers the numbers better than I do. My Yak with the 950KV Electrifly motor is pullin 13 amp, but at around 8600 rpm or so. It still has great performance, but it's a little light (25.5 ozs) compared to the other birds. We'll have to put the Macchi back on the Wattmeter and this time I'll RECORD the numbers..[:I]
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

How do I find the gearbox that you are useing?
Rabbit Leader
Posts: 1150
Joined: Thu Mar 15, 2001 11:37 pm

Post by Rabbit Leader »

Here's the link
http://www.e-flightline.com/gearboxes.htm

They make it in a 20mm and a 28mm version. JP's got one fom MEC, looks real stout too.

Cash
Cajun
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Joined: Wed Mar 28, 2001 10:22 pm
Location: USA

Post by Cajun »

From what I have seen in my research to date, this is just one of several new chemistries in cells we will be seeing in the next couple of years. The industry has finally gotten into high gear in battery development.

It will take a while to sort all of the data on these cells out. I have a DeWalt pack of A123 cells that should be here in a day or two and will be working with it to see what is the best combination. I personally like this cell for it's safety features. But, the Krion cell may be just as safe. I don't know what the chemistry is in this cell.

We probably need to keep all data on these experimental cells posted here for easy access.
Lee Liddle
Posts: 3330
Joined: Thu Jun 20, 2002 10:30 pm
Location: USA

Post by Lee Liddle »

Did some flight tests today with the Konion cells. 4s1p for 3696 weight 6.5oz and 4s2p for SSC weight 13oz. Results were good. Over 5 min of good power in each event. I also rigged up a 20mm 3300kv motor on a gearbox which shows good promise for a low amp 3696 setup.
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