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Two 3S A123 packs compared . Radically different charge methods.

Old 10-11-2007, 04:05 AM
  #1  
everydayflyer
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Default Two 3S A123 packs compared . Radically different charge methods.

I have been using A123 cells ,mostly from DeWalt 36 V ( E BAy) for a year now. One of my CBA Graphs was even published in a recent MA ,thanks Red.

I recently purchased an overpowered Ultra Mini Stick( formely owned by a moderator here) at a local Swap Meet that was a good candidate for a 3S A123 pack. This pack has been Zip charged at what most would consider extreme rates for most of its' life.Average rate of Zip charges 17A ,4 1/5 - 6 minutes per charge.

Most of the more important data is on the graph.

Mike I love the motor but the ESC was the pits.

Not everyone frequents the other site so a link for the curious.

http://www.rcgroups.com/forums/showp...16&postcount=1



Charles
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Old 10-18-2007, 01:00 AM
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No-one here finds 6 minute charge time intriguing?

Does any one here care to hazard a guess to how many cycles this pack will last befor droping down to 80% capapcity?

Flight # 164 ,cycle # 167 this morning and still going strong.
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Old 10-18-2007, 01:38 AM
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The charge time is intriguing and thanks for posting the graph. Can you explain how you've set up the zip charge?
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Old 10-18-2007, 02:17 AM
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Basicly it is a length of 18 gage Zip cord ( lamp / speaker wire) gater clips and Deans Ultras on oppisite ends of the wire. Lenght and gage of wire acts as a resistor to limit current. Eight feet of 18 ga. gives result as shown on graph. 20 ga. or a longer length would give reduced charge rate.
Link in first post to a rather complete thread on RC Groups.
Guess I cn do a little cut and paste.

From the other Forumn

I flew and data logged a 8min. flight and the charge following it.


Prior to first flight pac was zip charged last evening with a 1A stop point used. This morning cells were at 3.766 - 3.775 - 3.780


Second charge 27A @ start / 2:30 20A / stopped @5A

End of third flight cells 3.230 - 3.244 - 3.230
Start 26A
@ 1:30 21A cells 3.54 imbalance 0.005
@3:00 20.2A cells 3.56 imbalance 0.010
@ 4:30 19A cells 3.6 imbalance 0.010

@6:10 5A charge stopped cells 3.848 - 3.853 - 3.829 imbalance 0.014


Fourth charge

EOF cells @ 3.254 - 3.273 - 3.254 imbalance 0.019

Stopped charge at 13.5A 5:10

As a check used TP 1010C to top off.

1010C added 46 mAh in 1:18 cells 3.605 - 3.600 - 3.600 imbalance 0.005



My dual deep cycles were holding 12.42 under load and were at 12.71v 3 min. after last charge.

8 min. flights and 5 min. charges.

The fact that this pack is very difficult to remove for a pack change for additional flights make no difference now. I can live with a 5 min. wait between flights.

Summary:

A balanced pack stays balanced if not discharge to deeply. Charging at extreme rates does not effect balance to any measurable degree.
When charge rate drops to 15A it drops like a Hawk in a dive and from all indications pack is fully charged. This also happens to be the point were cells start to increase in temperature noticeable.
This 3S A123 pack now has 164 flights on it and 141 of the charges have been Zip charges.

I can not detect any change in performance.



Charles
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Old 10-18-2007, 05:00 AM
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A123's are looking better all the time. Thanks for being one of the pioneers in this research
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Old 10-19-2007, 02:12 PM
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It has been most interesting and enlightening.
It is really a shame IMO that A123 Racing only catered to the surface R/C ers and that us E Flight group had to turn to DeWalt / E Bay for reasonable priced cells and really learn the ends and outs of these cells on our own.

My feeling are that their initial cells were only developed as a means to an end. They needed funds to pursue bigger goals. I often wonder if they know their full potential themselves ,especially for our usage.

Charles
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Old 10-19-2007, 02:30 PM
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Originally Posted by everydayflyer View Post
It has been most interesting and enlightening.
It is really a shame IMO that A123 Racing only catered to the surface R/C ers and that us E Flight group had to turn to DeWalt / E Bay for reasonable priced cells and really learn the ends and outs of these cells on our own.

My feeling are that their initial cells were only developed as a means to an end. They needed funds to pursue bigger goals. I often wonder if they know their full potential themselves ,especially for our usage.

Charles
in the last month, i have seen several A123Racing adds in different magazines centered towards aircraft and touting 15 minute charge times on huge packs....

but, your right... only a few months ago, i never even heard of them and the only guy i knew that did was a car guy (thats not saying much, weez can be pretty shelterd here in Central PA!!!)
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Old 10-19-2007, 10:42 PM
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I have seen the ads but...
Model Airplane News Nov. 07
Featured in the ad is 6.6V 4600 mAh ,and two 6.6 V 2300 mAh (one stick and one side by side )along with their Sonic Charger.

My point is they only sell 2S and 3S packs and only sell a 2S-3S charger.

They are only interested in the R/C car market,IMO.
Horizon is the sole US Distributor for A123 cells now and Vendors have to pay dearly for the cells. It is much cheaper to purchase DeWalt 36 V packs from E Bay nd put the 10 cell contained inside to good use.

A123 bases the cost per cell on the cost of the DeWalt pack. They fail to account( discount) for the housing,battery management system and labor for assembly.

If one really wants to see the level of interest A123 Racing has in our useage of their cells then visit their Support Forum on RC Universe.


http://www.rcuniverse.com/forum/forumid_450/tt.htm
Charles
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Old 12-12-2007, 01:43 AM
  #9  
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The 3S A123 Racing / DeWalt 2300 mAh cells pack in post #1 which I have been Zip Charging now has 238 flights on it and 213 of the charges have been Zip charges.
Last fligh was 8 minutes in wind with more than normal throttle and pack took 2221 mAh to recharge according to Inspector wattmeter which was in-line.

$30 battery ,6-7 min. charges ,8 min. flights and it just keeps on going and going and going.


Charles
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Old 12-16-2007, 10:46 PM
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What does one of your finished 4cell packs weigh? I am wondering if I can smash a 4 cell Li-ion into a Brio 10 without to much weight gain. My 2100mAh 3 cell Lipos range from 140-180g depending on discharge rating.
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Old 12-19-2007, 04:53 AM
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I think one of the 4S pack weighs in at around 310g. I have the Solderless Power Tubes and I just weighed them today. 340g.........my 3S lipos are around 190g.............they are a little heavy and I am going to give them a try in my Airfoilz 260 extra this weekend.
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Old 12-20-2007, 10:47 AM
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Thanks Charles!

Larry
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Old 12-20-2007, 07:49 PM
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Just returned from another morning of flying. Cold for the South mid fourties overcast, breezy and misting rain.
Six more flights and Zip charges on my Mini Ultra Stick / 3S A123 DeWalt 2300 mAh cells pack.
Total of 263 flights , 240 Zip Charges.
Some can not read Graphs so here are the numbers from two of this mornings charges.
Both chargers were to between 11.7 and 11.8 volts and were between flights.


Battery at 9.57 volts
charged stated at 22 amps.
2 min. later charge at 16 amps. and 725 mAh into battery.
4 min. 150 mAh into battery
5 min. charge at 15 amps. and 1250 mAh into battery
6 min. charge at 13.5 amps. and 1725 mAh into battery
6 1/2 min. battery at 11.8 volts 1826 mAh into battery charge complete.

Another charge
4 min. 1200 mAh into battery
6 min. 1750 mAh into battery
6 1/2 min. 1886 mAh into battery 11.70 volts charge complete.

Non of these flights were to LVC . justnormal ripping up the sky flights of 8 minutes each.

I understand these should be only charged to 3.6 X3=10.8 volts and that max. recomended charge rate is 10A and that for max. service they should be charged at 3A when not in a hurry.
The facts / experience say that most flyers would rather charge in 6-7 min. than taking 15-20 min. and that being able to fly a plane for 8 minutes out of every 15 min. without having to remove the battery or purchase an expensive charge is great.
As I posted I have many very nice expensive chargers however I use non of them for this 3S pack except when checking pack condition as in a CBA discharge test.
I do check the balance from time to time and it is never more than 0.030 out of balance after being charged.

Larry you are most welcome.


As a side note I have a friend working on a 11.4 volts auto cutoff for us with Zip charging. No promises but if tere is enough interest he might be persuaded to produce a limited number of semi kits ( PCBs and componets) . Will just have to wait and see.



Charles
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Old 12-21-2007, 05:34 AM
  #14  
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Charles
I'm interested in getting started with A123 packs. What charger are you using with the ZIP cord? I have a Hyperion EOS 5i Lipo charger. Would it work?
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Old 12-21-2007, 06:21 AM
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Larry3215
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Originally Posted by everydayflyer View Post
<snip>

As a side note I have a friend working on a 11.4 volts auto cutoff for us with Zip charging. No promises but if tere is enough interest he might be persuaded to produce a limited number of semi kits ( PCBs and componets) . Will just have to wait and see.



Charles
Im interested. If nothing else in the circuit diagram and parts list.

As always, Im impressed Charles - great job

Larry
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Old 12-21-2007, 06:23 AM
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Originally Posted by gasser1933 View Post
Charles
I'm interested in getting started with A123 packs. What charger are you using with the ZIP cord? I have a Hyperion EOS 5i Lipo charger. Would it work?
The zip cord IS the charger.

All you need is a 12 volt auto battery as a power source.

The limitation is that it only works for 3S A123 cells. No other pack size will work.

Larry
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Old 12-23-2007, 12:34 PM
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I know I'm a little slow in finding this thread but thanks for bringing it to Wattflyer Charles.

My first questions were, what is involved in getting the cells out of the DeWalt pack? And how do you make your new 3s pack? Did some searching on RCG's and found a couple of nice threads by LBMiller5 with lot's of pictures. He doesn't make a 3s pack but there's enough information to figure it out.

Mini-HowTo - Disassembly of a DeWalt 36v Battery
Mini-HowTo - How To Build a Battery Pack from A123 Cell


Again thanks for sharing the info, this is very cool .
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Old 12-23-2007, 03:45 PM
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My first questions were, what is involved in getting the cells out of the DeWalt pack? And how do you make your new 3s pack?
There are many how to disassemble post. main tool needed is T-10 security bit ,about $2-3 at ACE Hardware . Note cheap sets fro Harbor Freight and such are worthless IMO.

Not much Assembly involved as the cells come already connected 10 in series. You just divide where appropriate and fold,glue,wrap etc. I add balancing leads to all of mine.




Opening the pack.

http://www.slkelectronics.com/DeWalt/packs.htm

Easy packs

http://www.slkelectronics.com/DeWalt/hints.htm


Charles
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Old 12-27-2007, 01:16 PM
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Does the Zip cord have any other function than to be a fixed resistor? For example, does it's resistance change over the course of the charge?

My layman's assumption is that the resistance of the zip cord increases as the cord heat ups over the course of the charge, thus helping to reduce the delivered current as the charge progresses. Is this right, or is it just a fixed resistance?

If it is just a fixed resistance, why not use a resistor? I suppose I could probably answer my own question here by saying that a resistor that could handle this kind of watts would probably be expensive.
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Old 12-27-2007, 03:48 PM
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If it is just a fixed resistance, why not use a resistor? I suppose I could probably answer my own question here by saying that a resistor that could handle this kind of watts would probably be expensive
As it does get warm its' resistence does chage a little but for all practicle purposes it is a fixed value.

The normal charge rate of my pack after a flight results in a charge rate of 250 watts and yes a 250watt resistor would be more expensive and you still need wire somewhere to get juice from the source to the pack..

At the local Dollar General Store I purchased duel 8' 16ga. indoor extension cords (zip line) for $2.


and then there is this

http://www.wattflyer.com/forums/show...7&postcount=10
Charles

Last edited by everydayflyer; 12-28-2007 at 06:39 PM.
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Old 01-02-2008, 03:19 PM
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Results of latest Zip charging by way of PC PS Zip cord(16ft. / 16 ga.) and a solid state charge terminator.


Old 3S A123 2300 discharged to 2 volts per cell. Several minutes later .
Open volts 8.10
Charge started 17A
1 min. amps. @ 11.5 / 250 mAh delivered
5 min. amps. @ 10.1 / 925 mAh delivered
8 min amps. @ 9.75 / 1400 mAh delivered 10.52 under charge
11 min. amps @ 8.9 / 1880 mAh delivered 10.65

12:20 11.45V Terminator stopped charge 2053 mAh delivered
13:40 volts decayed to 10.5? Terminator fired up and added 24 mAh (2077 total)

15 min. 10.84


Note this is not the same battery used in MUS.

For those who desire addational details.

http://www.rcgroups.com/forums/showp...&postcount=194


Charles
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Old 01-03-2008, 12:17 AM
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Thanks for keeping us posted Charles .
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Old 01-03-2008, 12:42 AM
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Originally Posted by Larry3215 View Post
Im interested. If nothing else in the circuit diagram and parts list.

As always, Im impressed Charles - great job

Larry
Here you go.

http://www.rcgroups.com/forums/showt...22#post8844692
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Old 01-03-2008, 04:26 AM
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Perfect!

Thanks Charles!

Larry
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Old 01-05-2008, 09:42 PM
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everydayflyer
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In case anyone is curious about size ,etc.

Circuit DIY Thread :

http://www.rcgroups.com/forums/showt...22#post8844692

Both myself and my son have these in use now and they are doing great.


FYI My 3S MUS pack now has 281 flights and 258 zip charges on it.

Charles
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