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View Full Version : 20C Lipos...A Myth? I investigate!!!


DIALED/CHUCK
12-07-2005, 03:13 AM
Hey Guys,

Something interesting came afoot today and I wanted to 'share this with the group'.
At this time, I am a little concerned, hurt, and angered if what I have found today is in actuality...'the truth for all new 20C Lipos'

Over the Thanksgiving holiday, I went shopping! Not the kind of shopping that my wife does; no I did not go window to window admiring the latest purses and kitten-heels. Mine was a day of shopping on-line...for Christmas presents...for me.

I came across a hot sale on some of the new Polyquest-Twenty lipo batteries. And, being a huge proponent of Polyquest's 12-15C line, I snapped out the credit card and ordered several. Needless to say, I was not the only guy doing the same thing as the notice arrived telling me they were now backordered due to huge response.

Today, one of my packs arrived. A new Polyquest-Twenty 2100mAh 3s pack boasting a constant discharge rate of 20C (or 42 amps) and bursts even higher. I tore open the box and noticed...WOW...these things sure are BIG.

As I handled the cell I noticed it was about the same size as my Polyquest 3100mAh 3s' rated at 12-15c. Out to the shop I went to solder on a deans and slap it on the Astro 109 to test. As I set the pack on my table...shock set in. This 2100Mah 20c pack is the same exact size as my 3100mah 12-15c pack....I mean EXACTLY. I picked both packs up in opposite hands....BLAMMO!!! They both felt EXACTLY the same weight.
After weighing BOTH the 2100 is 1 oz lighter that the 3100....to the gram!
But, noticing the new pack design of lighter shrink and the removal of 10 percent of the shrink, and removal of the polyquest 'battery foam' (now a tissue paper-type material) and a new ligher gauge wire than was on my discontinued 3100 12-15c....my curiosity grew.


Now, I know some distributors of Lipos have done a marketing twist and taken a 2100 10C and repackaged it as an 1050 20C in order to raise prices and increase profits while getting in on the new 20C buzz-market. Again, I am a marketing guy by trade myself and I understand the dance we do sometimes to bolster profits and excitement...BUT COULD THIS BE THE SAME WITH MY EXPENSIVE NEW POLYQUEST PACK?

I did some comparative testing on the cells under the same load (both the new 2100 20C polyquest and the discontinued 3100 12-15C polyquest) and I think you will all be interested in the results.

COULD THESE BOTH BE THE SAME PACKS?

COULD THESE BOTH HAVE THE SAME mAh and discharge rating?

IS THE 20C LIPO MARKET NOTHING BUT A MARKETING GENUIS MYTH?

History will decide.....

As a side note, if this IS true...it is NOT illegal. They are being 'honest' about the rating...for example...I drive a 04 Mountaineer, same engine and setup as a FORD EXPLORER...but I paid 4,000 more for it than an Explorer...simply to drive a Mountaineer.

Results forthcoming.

Meantime...Stay sharp, sleep tight, and don't let the bad marketing people get you!

--C

Geoff_Gino
12-07-2005, 05:48 AM
Hi ChuckD

Good spot - I will be watching and waiting with bated breath for the results.

Geoff

watt_the?!
12-07-2005, 07:04 AM
Chuck...bingo!

that is why i started a thread asking about what the difference is between the 10C and 20-30C packs- chemical wise and mechanically...

no one could answer.

The high discharge packs are heavy....why?...shouldnt they weigh the same but have some new chemistry that enables higher transfer of energy?

maybe they have some new chemistry that allows higher discharge but higher weight per unit of energy.....if that's so, then why dont you just parallel up a couple of packs to achieve the same?

If i put a 10C 3s2p 3000 pack up against a new 20C 1500 pack does it hold it's voltage just as well under load?...what is the weight difference (minus tabs and wiring)?

the next ''clue'' is....there is only a handful of LiPo manufacturers on the planet..surely they all have access to the same technology...or if they dont, they soon do... so how come ALL the LiPo brands arent claiming the same discharge rates?

I also hear anecdotally that peeps are pulling the same flight time out of a 1200 pack as they did with their old generation 2000 packs.....this is a dead giveaway IMO. How can it be?...answer..it cant. If you are pulling the same amps in the same plane and just swapping out batteries, then you are pulling out the same capacity...

i.e. a 1200mah pack will give you 1200/2000 x flight time that the 2000 pack did.

if it gives you the same, either the 2000 isnt 2000...it is old and cant give 2000 anymore (or hold 2000), or the 1200 is holding more than 1200.

I suspect it is somewhere in the middle.

but of course this is all speculation...but something IMO just doesnt add up.

One of my pet peeves is how the public instantly go for the high C packs. Why?

6C is 10 minutes flying, 8C is 8.125 minutes, 10C is 6 minutes, 15C is 4.5 minutes, 20C is 3 mins and 30C is 2 mins...and it is less before the BEC cuts in.

the higher the discharge you have, the less life the pack achieves in terms of cycles also.

and so on.

Rugar
12-07-2005, 10:25 AM
Chuck,
Don't leave us hanging to long now! ;)

DIALED/CHUCK
12-07-2005, 11:34 AM
I will have the results later today....BUT READ TIM/WATT-THE's post....

Tim is like me in that he prolly can walk into a movie and tell you how it will end 15 minutes in! ;)

--C

spark
12-07-2005, 04:30 PM
All you need to do is charge them with a charger that shows how many milliamps were put into the cell to determine their true capacity. If you start with a fully discharged cell, if it puts 2100ma into them they are 2100ma cells,

hoppy
12-07-2005, 05:45 PM
FWIW
16/22C PQ 2100, 41 x 121 x 17, 172g
12C PQ 3100, 40 x 114 x 23, 196g
20C PQ 2100 44 x 133 x 19 173g

Some PQ discharge graphs-
http://www.elektromodellflug.de/akku-test/polyquest.htm

jfcgnv
12-07-2005, 11:53 PM
Chuck, You have hit on exactly what I have found out about another battery Co from the UK. I was thrilled when I flew my new battery packs. I had a 1200 and a 1800 pack. I and several of my club members have flown these packs for over two months and we were amazed at the flights we were getting. If fact like Wat_The says ( I believe he was refering to me) something didn't add up. First the 20C battery was heavier than it should have been. About the same weight as the 2000 pack. We were all trying to figure out how a 1200 pack could perform almost identically to a 2000 pack. Even the charge Ma were almost identical. The first tip off should have been when my 1200 pack took 1300 Ma to charge and the Bec didn't shut off in flight.

If this type of marketing is not un- ethical it surely is misleading. I for one will not buy from this Co. again. When I purchase a 1200 pack I expect to pay for and receive a 1200 pack. When the fact is, what we thought was extrordinary performance was just average for the correct Ma battery that it actually was.

watt_the?!
12-08-2005, 12:02 AM
FWIW
20C PQ 2100, 41 x 121 x 17, 172g
12C PQ 3100, 40 x 114 x 23, 196g

Some PQ discharge graphs-
http://www.elektromodellflug.de/akku-test/polyquest.htm


even this is somewhat interesting...

the 20C packs are 172g/2100 mah = 0.0812 g per mah, or 12.2 mah per gram.

The 12C packs are 196/3100 mah = 0.063 g per mah, or 15.8 mah per gram.

So the mah density is actually better for the 12C pack than the 20C pack.

Volume wise the 20C pack is 84337 mm cubed and the 12C pack is 104880mm cubed.

this translates to 490mm cubed per gram for the 20C pack and 535mm cubed per gram for the 12C pack.

i.e. you get more energy per gram and per volume in the lower discharge pack.


either way...per gram it is 12.2/15.8 = 23% difference. And the difference between 3100 and 2100 is 33%.

So are you getting 20C/12C difference (66%) more discharge capability?.... are you actually getting 1000/2100 = 47% more mah?

the figures suggest otherwise. like something in between.

Bob_CO
12-08-2005, 12:22 AM
/GrabPopcorn

Watches the show :)

cyclops2
12-08-2005, 12:25 AM
More energy sounds right from a engineering point. Less heat means the plates can be closer together and have more capacity. Higher discharge means more heat and more thermal insulation and less capacity. Was that way in the high temperature Nicads.

watt_the?!
12-08-2005, 12:30 AM
/GrabPopcorn

Watches the show :)

i love this place...

DIALED/CHUCK
12-08-2005, 01:20 AM
FOREWARD:

Opening tonight, let's be honest about what this is leading to....
Will we 'find a witch' or 'out the villians'? Probably not...

The reason I am doing this is moreso a quick lesson in perception, reality, and marketing. I am of the 'new' and 'quirky' (according to the old school guys) who believes in being straight with the marketplace...and that your biggest success comes from satisfying your core customer and letting them do your advertising for you. This is not about 'sticking it to the man'...rather, informing the customer.

But first...thanks to hoppy for these specs.


Originally Posted by hoppy http://www.wattflyer.com/forums/images/misc/backlink.gif (http://www.wattflyer.com/forums/showthread.php?t=2831#post27047)
FWIW
20C PQ 2100, 41 x 121 x 17, 172g
12C PQ 3100, 40 x 114 x 23, 196g

Some PQ discharge graphs-
http://www.elektromodellflug.de/akku-test/polyquest.htm


...the difference in these packs is a different shrink, 10 percent less of it...the removal of the 'polyquest foam' and some new spacers between the cells...and a lighter gauge wire.(suprising as it is supposed to be higher discharge). On my scale (Pitney Bowes) the 20c 2100 comes in at exactly one ounce lighter than the 12/15c 3100.

---------------------

The Saga:


"These 20C's seem like under-rated 12/15c cells"

Un-ethical? ...depends on how one views the situation.
PS...there is no real 'legislation' on lipos at this time in any 'quality' aspect. Therefore, I could sell a batch of 4000mAh cells that actually only put out 1000...and no one can really do anything. Hire a lawyer, I blame the maker, your lawyer calls Korea and the maker laughs at them and hangs up the phone...closes shop...and opens a month later under a new name producing new cells.

I am a firm believer in Karma...what you put out, comes back; I have seen it too many times. I simply wanted to put this out there and let the group decide.

------------

The Test:

o
It is very cold here at my home in Virginia Beach; 27 degrees...still, out in the shop it is 39...still too low a temp to do any 'REAL' testing...and lord knows I cannot bring these things in the house to test....my wife would have my head.

I DID, however, earlier this afternoon, get to put the BOTH 12/15c 3100mAh lipos and 20C 2100mAh lipos under a determined 26 amp load for 30 seconds on the bench.

Here are some of the findings....INTERESTING!!!!

Lipos charged to 12.8V on an ASTRO109

Discharge setup
CC PHX 40
Mega 16/15/4
APC 6X5.5 prop

VOLTAGE and MAH used in 30 second test:

20c 2100 - 238mAhs 12.14V after 60 second rest
12/15c 3100 - 253mAhs 12.22 after 60 second rest

This was a constant draw of 26 amps...but on BOTH PACKS the amp draw dropped to 22-23amps after about 10 seconds...the cold had a factor, I am sure.

As soon as it warms up outside, I will have a flight report...but from my standpoint...these are looking about as close as it can be...and I would think the small differences could be seen on two of the same packs (2 20C's or 2 12/15c's) in a test of this nature.

Feel free to opine...

Thanks for taking part, guys...it means a great deal to me that people care about this... I am not on a crusade or anything...just bringing up an educated conversation...and apparently I came to the right place.

You are pros, one and all.

I am 'out' for the next 4 days on business...then off for the holidays (MORE TIME ON THE BOARDS!!! YEAH!!!) . I'll check in from the 'proverbial road' when I can.

--C

Klique
12-08-2005, 01:57 AM
Chuckee go to rc lipos .com they have the charts with the facts.They are a verry stong 15 c while the old tens were really 8c.:) I know the owner he doesnt BS.:p like lobby lobbie.
Ck

DIALED/CHUCK
12-08-2005, 03:10 AM
Chuckee go to rc lipos .com they have the charts with the facts.They are a verry stong 15 c while the old tens were really 8c.:) I know the owner he doesnt BS.:p like lobby lobbie.
Ck


Ck...it's about time...:D

...like I said when they first came out and we were having one of our 2am phone conversations and sharing a beer 3000 miles away...I think they are actually 15c/20c burst. However, I know you prolly have seen the several whom are selling them under the premise of 20C/25C

I cannot wait to test these in the field. But, at this point...I would rather parallel two 12/15c's at 2000mAh to get equvalent weight and amp draw...but a nice run-time twice that of a 20C. ...problem is 12/15cs are a dying breed.

But again...till I can get some 50+ degree temps here at the beach, I cannot conclude any 'finals'.

Again...nice to see you chiming in....I gotta hit the rack.

--C

Klique
12-08-2005, 04:27 AM
A perfect set up for a 36' inch wing, work these numbers on medusas site.Here is the spex.
028 40 1700 afterburner motor
apc 5 / 5
alternate 5.5/4.5 apc
2, 3 s 2500s in series for 22 volts.Also use the 3300's and the 3700's dep on prop and planes.I also use a 2s and a 3 s in series for 5 s on some of these configs.These higher voltage set ups are way eficient compared to 3 and 4s setups.:)
ck

hoppy
12-08-2005, 04:45 AM
I've updated the PQ info to include the old cell and the 2(?) new cells.

ACWorld sell one they call a 16/22C - It is the PQ 2100, 41 x 121 x 17, 172g
Hobby Lobby sells one they say is 20C(continuous) model - 20C PQ 2100 44 x 133 x 19 173g
Old 3100 12C - 12C PQ 3100, 40 x 114 x 23, 196g
NESail sells a PQ20 2100 which is listed as 44 x 121 x 20 @ 177g
AlleRC calls them a 15/20C pack.

Bob_CO
12-08-2005, 05:03 AM
I think the real test is to discharge them to 9v and see what they take going back in.

Geoff_Gino
12-08-2005, 06:13 AM
I think the real test is to discharge them to 9v and see what they take going back in.

Another test would be to see how long they hold their voltage at max draw. How long does it take the voltage to drop at max current to bring the ESC to cut-off.

There has to be a marked difference between a 15C and 20C pack.

Geoff

savydad
12-08-2005, 01:14 PM
And honestly, who wants a 3 minute flight time? Unless you are in a pylon race (are they even that short?) a 20c lipo is really not needed, IMHO. The only advantage I see is that they will hold voltage better under a smaller load. Anybody correct me if I'm wrong here, but that's what I see.

Todd

Matt Kirsch
12-08-2005, 01:44 PM
A 3 minute flight assumes you fly around at full throttle all the time, though. If you're like most people, you're only near the full 20C draw at full throttle, and only near full throttle in short bursts because your plane is so light and overpowered. Besides, even 20C rated packs won't last long if used constantly at 20C. That rating is achieved in lab conditions, not in the belly of a super-inslulated flying beer cooler.

On the subject of heat, I have two words that explain why a 20C rated cell is larger and heavier than a 10C of the same capacity: THERMAL MASS. Higher discharge rates generate more heat, and the additional thermal mass helps dissipate the heat. Then there's the whole clown car analogy explaining how physically larger cells allow for more efficient discharging... Do I really need to get into that? :D

The point of a higher-rated cell is twofold:
1. Pack holds higher voltage under load.
2. Saves weight by allowing you to run with a single 20C 2000mAh pack instead of two 10C 2000mAh packs in parallel. The savings may not be 50%, but 25-40% is typical, and when you're into the larger planes, that means several ounces.

I'm not saying that PQ didn't just derate their 3100mAh cells, but the larger-heavier thing isn't new. There was a similar discussion over on ezone back when Kokam released their line of 20C packs. I say we see if the proof is in the pudding.

cyclops2
12-08-2005, 02:08 PM
I pulled out my Digi-Key catalog and looked at all the different classes of Panasonic Nicads. They must be old fashioned, because for a 1200 mah SC the size and weight changes with each class, from standard to hi-temp., to Super Duper. Panasonic does vary the construction , size and chemistery. Panasonic still the best. Oh yes, I still have 10 year old Pans that charge up to OVER rated capacity.
They are one company who does make a quality product. :)

DIALED/CHUCK
12-09-2005, 01:17 AM
On the sidebar:


A perfect set up for a 36' inch wing, work these numbers on medusas site.Here is the spex.
028 40 1700 afterburner motor
apc 5 / 5
alternate 5.5/4.5 apc
2, 3 s 2500s in series for 22 volts.Also use the 3300's and the 3700's dep on prop and planes.I also use a 2s and a 3 s in series for 5 s on some of these configs.These higher voltage set ups are way eficient compared to 3 and 4s setups.:)
ck


Yo CK...

Try getting hold of a Graupner 7X7 SPEED PROP. Trim it down to a 5 inch and balance; I think you will be pleased with the results. Lemme know what it does.


-------------------------------

Long day today...13 hours in day one of a annual fundraiser the wife and I do for a children's hospital...when I got in my car, the cell had 6 (yes, 6!) messages about this thread; apparently we have stirred up a bee's nest.

Everyone want's to know what the deal-e-o is....

I have next Monday off...and if the weather holds, I am hoping to get out in the field with these cells and really run them...

Later on, brothers.

--C

Bob_CO
12-09-2005, 04:46 PM
I guess I am missing the point of what flying the packs does to see if the 20c packs are just 3100mah packs. Don't you need to discharge one of each to a known point and then charge them to determine the capacity? How they are discharged doesn't really matter. I mean if they are both dicharged with the exact same load and down to the exact same voltage it doesn't maktter if it is a lightbulb or prop that was used, right?

Geoff_Gino
12-12-2005, 06:40 AM
Hi ChuckD

Been thinking and perhaps the best test is setting up a 10C and 20C pack and going for max discharge (keeping the discharge at the max of the 10C pack) and timing them to the cut-off voltage.

Just a thought.

Geoff

Matt Kirsch
12-12-2005, 04:29 PM
Well, be careful with that... Even the 10C rated cells aren't designed to run 10C continuous from start to end.

DIALED/CHUCK
12-13-2005, 02:03 AM
Maximum Discharge: The Final Repot On The All-New Polyquest “Twenty” Lipos.


As I said when I first bought a batch of Polyquest 20C’s, I was chaginned when they arrived at my home only to find the 2100mAh 20C was the same size as my 3100mAh 12C. After weights and measures…it was but an ounce lighter than the 3100mAh Polyquests I own…and immediately, I was certain these were simply under-rated 3100mAh cells…after all…for companies to do such is not untruthful…simply a marketing angle that would gain interest and excitement in the lipo market.

Out to the field I went to try my 2100mAh 20C Polyquest against my 3100mAh 12C Polyquest. The weather... beautiful; 51 degrees, wind was solid out of the west at 15-18mph, which, would give me a nice amp-draw coming back up the strip on my passes.

The wing I was flying was set up with a Het Typhoon 4W, Castle Creations 35amp ESC, and an APC 6X4 prop which draws 24 amps on my bench with my test pack that is rated to for a constant draw of up to 70amps. I set up the timer on my 9C to start at 50 percent throttle (as I rarely fly below 50 percent unless I am landing). After landing, I IR-temped the cells inside the wing with the battery-panel open.

Here are the stats:

Polyquest 3100mAh 12C
Flight Time: 12:14
Temp on Landing: 98 degrees

Polyquest 2100mAh 20C
Flight Time: 6:48
Temp on Landing: 81 degrees.

My conclusion is that these are indeed different cells…and the 2100’s impressed me in that they were so cool upon landing; and I really beat both cells with lots of quick u-turns and vert. I must say as well, the 2100 20C did not seem to ‘fall off’ in power until about 30 seconds before dead-stick…while I can always tell when my 3100’s are about 5 minutes out of cut-off. Personally, I was glad these were NOT the same cell…they are different cells…flight time and performance made the fact quite clear.

The only question that remains in my head is ‘what is with these cells’? It would almost seem to one that the chemistry is exactly the same inside the lipo and the cell-packs have simply been extended by an inch.

The many questions I hear on the street are:
Will these cells be an advantage with the weight gain? Is it still more effective to fly 2 12C 3s packs in parallel rather than 1 20C pack? Is the cost factor ‘there’ for customers to really get on board with 20C? Is 20C a winner?

History will decide.


Thanks for reading…talk soon!

--C


ps....GOOD TO BE BACK....4 days at the fundraiser for the local Children's Hospital and twelve hours a day of shouting an hollerin' paid off; the good news is that the wife and I managed to raise $356,000 for the kids in three days...a record breaker!

cyclops2
12-13-2005, 02:59 AM
Chuckd. Are you interested in a possible set of Danish Air Force Saab Draken plans? They E Mailed me for my address. Maybe? I have no idea what they will send. Should I post you? Rich.

DIALED/CHUCK
12-13-2005, 02:18 PM
Clops... Thanks...send me a PM and lets discuss.


----------

Also....

Some personals on 'Would I buy more Polyquest 20's?' after having 4 laying around now. My answer is: 'not at this time'....I need a fuselage to put them into as they are so tall...and well, I am a wing-freak so all of my lipos need to be 25mm and under. True the 2100 20C and 3100 12Cs fit in a Zipper-Wing; but that is in 3s...and they just barely fit in there...
Unless I get custom packs made in weird block arrangements (did that once with another wing..not cost effective)...I cannot go 4s with these...


Looking forward to testing some new cells soon....I have a long two months of winter ahead here in the mid atlantic...and it is now officially slope season at the beach.


--C

Matt Kirsch
12-13-2005, 02:22 PM
That's very encouraging news about the cells' performance. Competition breeds price wars :)

I'll tell you, I sincerely doubted that a heavier, lower capacity cell with higher discharge capabilities would have any advantages. Run the numbers, though:

1. The 20C packs are more expensive than 10C packs of the same capacity, but nowhere near twice as expensive.
2. The 20C packs are heavier than 10C packs of the same capacity, but nowhere near twice as heavy.

DIALED/CHUCK
12-14-2005, 02:16 AM
The last entry into this thread for me about the 20C's peformance.

2100 20c took 2098mAhs in the charge after another flight today. The numbers are 'on' as they say.

Later on,

--C

Car&Bike Racer
12-20-2005, 11:06 PM
I think the extra weight and lower internal resisitance is because of bigger electrodes. MY 2500xp's gave much more punch than my 3100 12c pack, I think a better rating would be 15c for the xp/20's and 10c for the 12c's.

I'm still not sure what would be better, high IR + higher mAh or lower IR + Lower mAh. If you discharge your packs at 10 mins or more then the first option would be the obvious choice, but at 5mins or less the second option is more appealing.

Max watt's per gram is a nice way to compare. But I would say the second type needs to have a significant advantage to outway the fact that you will have less runtime.

DIALED/CHUCK
12-20-2005, 11:44 PM
Car-Bike....

I am glad you posted....

I actually have been running mine for a a little over a week....

My 3100 12Cs exit the plane at 10.4-11v

The 2100 20's exit at 9.3-9.6 every time now...

Both packs were NEW and now that the break-in is over...I must say....(gulp)...I am favoring the 2100's on a 24 amp draw app.

Sometimes...it is good to have my disbelief shattered. (sometimes)

These cells appear to 'bring it' until the bitter-end...something I had never seen in any lipo yet. It is nice and my flight time is up to 7 and a half minutes on the 2100 according to the 9c's timer...I plan on getting a few more for a new app now.

--C