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Old Apr 16, 2007, 03:07 AM
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A123 long term: 1st 1,000 CYCLES done, 2nd +800cycles highC done, 3rd to 0V going on

Hi guys,

Been'out (too much office work) lately... but took advantage of the time.

One of my Dewalts was for a friend looking just for 3s packs, and he decided to "donate" the last cell to the science (thanks Javi), so I had a loose A123 cell to play with.

And after some "burn in" cycles and some "torture tests", I decided to leave the cell in one of my chargers, cycling.

First 100 cycles were at 3C charge and 6C discharge (6'9A charge and 13'8A discharge). After those 100 cycles, cell was cycling at the same 2150 average mAh. No looses.

Then I have done 200 more cycles at 5A charge and 10A discharge. After 100 cycles, cell was doing exactly the same numbers (from 2090 to 2170 mAh charging-discharging, say 2150 average). The last of those 200 cycles saw the numbers go a bit lower, say average 2080mAh (from 2050 to 2095, all under 2100).

My voltage cuts are programmed at 3'650V for charges, 2'300V for discharges, on all those 300 cycles done.

I am yet a bit out of time, and the cell is still cycling (going for 400), but as soon as I can I will give you some discharge graphs "before and after" to see how it looks.

I am impressed, but to be honest I was not expecting a different result from a "long term" test on a A123 cell. I fly them since past september-october and cannot be happier with them (I use 3s and 7s packs).

Fly as much as you can!

Regards

Josep
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Old Apr 16, 2007, 03:57 AM
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Son, Norway
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Nice piece of science, Josep!
I have just installed 4S A123 in my Eco8, and it's hovering with the same discharge rate as you use . When I say installed, I mean putting cells where there are room. The size and form factor is one of the main drawbacks of these cells . Keep us posted, and maybe do some over dis-/charging later.

Fred
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Old Apr 16, 2007, 06:24 AM
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treehog's Avatar
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Joined Jan 2004
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1000 cycles easy with abuse 2000 with care and nobody disputing that

Really most users will never use more than 500 cycles
The problem is the bad power density for small plames

good luck its hard work doing 500 plus cycles but I figure your results will only confirm the offiical figures plus minus 20%

100 cycles to 300 cycles is very inteeresting to know in lipos

Ralf

PS
see you are based in Madrid
is there a good electric LHS in madrid if I pass through there in june
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Old Apr 16, 2007, 08:27 AM
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United States, CA, Sunnyvale
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awesome! I always wanted to see actual tests on these cells. 400 cycles sounds good. I wonder if they would really make it to 1000.
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Old Apr 16, 2007, 09:09 AM
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Ralf,

Yes, no less than half a dozen good Local Hobby Shops in Madrid with nice stocks. See www.miliamperios.com and ask or search there: Aeromodelismo Serpa, Speed Hobbys, Aeromodelo, Vazquez Ramirez, Piper. Here you have five of them.

One thing I partially mislead: the programmed end voltage on the last 200 of the 300 cycles was 3'70, not 3'65V. The charger I am using for this (Robbe MaxAmps latest "Li" version) "slows" the charge at the end of the CC part going into the CV, this is why I decided to "up" the V a bit.

After I have some time to show the discharge graphs, I decided to do some 25 or 50 more cycles in the same way to see if the small losses detected lately confirm (or not), and then go ahead with say 100 more cycles "abusing" the cell in final voltage: I will program the V cut up to 4'1V, as if you use a charger ready for LiIo but not for "LiFe", to see how much -if any- is the damage done this way (remember A123 systems is not very clear about this).

Regards

Josep
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Old Apr 16, 2007, 09:46 AM
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Josep,

Thanks for doing the testing. I think this information is not only very helpful to me but also to many others who will be using a123 cells now and in the future.
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Old Apr 16, 2007, 10:05 AM
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Europe, Austria, Burgenland
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hi, maybe missed it:

how many cells do you measure ?


i think its a difference if you charge to 4,1Volt a single cell
(it will realy not go over 4,1Volt)

or you charge maybe 4s of the cells to 4,1Volt/cell-setting,
because here:
if the cells show little out of balance, a single cell can easily go over 4,1Volt which may effect lifetime more ?!?
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Old Apr 17, 2007, 01:58 AM
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Hi,
I am doing this to a single cell. And not yet started the "final torture test" (going over 3'7V at the end of charge).
Regards
Josep
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Old Apr 17, 2007, 02:16 AM
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Quote:
Originally Posted by armengol
Hi,
I am doing this to a single cell. And not yet started the "final torture test" (going over 3'7V at the end of charge).
Regards
Josep
This is not necessarily torture. 3.8V is recommended cutoff for 10A charging for instance...
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Old Apr 17, 2007, 02:16 AM
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great stuff to read, i too have been using since septermber 06, right now i have over 100 of these cells in use and have not killed any.
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Old Apr 17, 2007, 04:26 AM
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Quote:
Originally Posted by WimH
This is not necessarily torture. 3.8V is recommended cutoff for 10A charging for instance...
Where this information came from?
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Old Apr 17, 2007, 05:50 AM
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Quote:
Originally Posted by coro
Where this information came from?
Don't remember exactly, but it's within "specs":

http://www.first-products.de/specsenglisch.htm

I think the higher voltage compensates for the losses in the charge cables at "higher" currents...
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Old Apr 17, 2007, 08:11 AM
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Quote:
Originally Posted by WimH
Don't remember exactly, but it's within "specs":

http://www.first-products.de/specsenglisch.htm

I think the higher voltage compensates for the losses in the charge cables at "higher" currents...
Than You.
So, maximum is maximum. I should appreciate their work,
but I am a little conservative, especially now, after the Age of Lipos.
I think that I do not like it
My charger measures wire resistance, counts the voltage drop and THEN increases voltage, so that my voltmeter shows 3.600V hooked directly to cell, in CV phase (not exactly steady, but allmost).
I like that, much.
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Old Apr 18, 2007, 02:15 AM
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Coro what charger are you using?
Regards
Josep
PS: I will be in Prague in around four weeks
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Old Apr 18, 2007, 06:37 AM
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FMA Direct BalancePro HD 6s. I have been writing about this charger too long in forums, so I did finally purchased one, and it is really all true. I am impressed.. and I have OLED display working with its data output allready, so.. this is the best charger I have ever seen.
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