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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> A123Racing Support >> Better with higher temp?
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Better with higher temp? - 5/28/2007 3:14:38 AM   
13BRV3


 

Posts: 235
Joined: 10/14/2006
From: Navarre, FL, USA
Status: offline 		Greetings,

I'm still fairly new to these cells, and recently tried a 4s1p pack in my E3D. It flew great, but I was curious how much power was being generated by the pack. Attached is a graph of a 2 minute full throttle run. I was pretty surprised to see the amps and voltage both go up during the run, particularly since this is really pushing the pack pretty hard.

On the other hand, Bill Dube' (killacycle.com) says the cells put out more power when warm, so maybe this is totally normal. I've never seen it in any run before, but then I've never pushed much more than 35 amps before.

Is this normal? Seems pretty amazing that they get stronger when abused

Cheers,
Rusty


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< Message edited by 13BRV3 -- 5/28/2007 3:16:03 AM >
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RE: Better with higher temp? - 5/29/2007 12:14:22 AM   
13BRV3


 

Posts: 235
Joined: 10/14/2006
From: Navarre, FL, USA
Status: offline 		I repeated this experiment today, using my other pack, and got the same result. This time I ran it into the dirt, and measured the temp of the pack afterwards. It was a pretty toasty 135 degrees F. It does seem that heat enhances their performance.

Cheers,
Rusty


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(in reply to 13BRV3)
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RE: Better with higher temp? - 5/29/2007 1:06:09 AM   
Red Scholefield



Posts: 4780
Joined: 12/8/2001
From: Newberry, FL, USA
Status: offline 		True, from your discharge curve the pack puts out more as it heats up. What this doesn't tell you is that when you get this dip in the discharge voltage curve you are negatively impacting the cycle life of the pack.

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(in reply to 13BRV3)
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RE: Better with higher temp? - 5/29/2007 2:23:33 PM   
13BRV3


 

Posts: 235
Joined: 10/14/2006
From: Navarre, FL, USA
Status: offline 		Hi Red,

The plane would never be flown this way, so I'm not worried about how hard this is on the cells. Still, this is all within the continuous rating for the cells, so I wouldn't expect that it's too bad for them. Will I only get 800 cycles instead of 1000

BTW, I'm really liking these cells

Rusty

(in reply to Red Scholefield)
       Post #: 4

RE: Better with higher temp? - 5/29/2007 7:02:57 PM   
Red Scholefield



Posts: 4780
Joined: 12/8/2001
From: Newberry, FL, USA
Status: offline
quote:

ORIGINAL: 13BRV3

Hi Red,

The plane would never be flown this way, so I'm not worried about how hard this is on the cells. Still, this is all within the continuous rating for the cells, so I wouldn't expect that it's too bad for them. Will I only get 800 cycles instead of 1000

BTW, I'm really liking these cells

Rusty



In all reality, it is more like 8 cycles instead of 80.


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Red S.
AMA 951 Leader Member

(in reply to 13BRV3)
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RE: Better with higher temp? - 5/29/2007 7:43:22 PM   
13BRV3


 

Posts: 235
Joined: 10/14/2006
From: Navarre, FL, USA
Status: offline
quote:

ORIGINAL: Red Scholefield

In all reality, it is more like 8 cycles instead of 80.



Wow! Are you saying you think A123 cells are only good for 80 cycles under good conditions??? Surely not...

Rusty

(in reply to Red Scholefield)
       Post #: 6

RE: Better with higher temp? - 5/30/2007 6:29:08 PM   
A123 Racing


 

Posts: 102
Joined: 8/25/2006
From: Hopkinton, MA, USA
Status: offline 		Hello Rusty,

Our Batteries are Rated for Up to 1000 Full Discharge Cycles at 10C (assuming you don't over charge them, short them, or anything like that). Heating the cells does have an impact in the number of cycles, but it is not a ten fold difference. If the cells are run Hot (but not beyond their recomended 70' C limit) then the cycles lost are in the 15-25% range. It's imposible to nail down an exact number as every application is differnt, but that is an accurate window for most users.

Hope this Helps

Brian

Power . Safety . Life


(in reply to 13BRV3)
       Post #: 7

RE: Better with higher temp? - 5/31/2007 2:57:46 AM   
13BRV3


 

Posts: 235
Joined: 10/14/2006
From: Navarre, FL, USA
Status: offline 		Thanks Brian. That confirms everything I thought I knew about these cells. I don't understand Red's comments at all.

Cheers,
Rusty

(in reply to A123 Racing)
       Post #: 8

RE: Better with higher temp? - 5/31/2007 1:09:35 PM   
Red Scholefield



Posts: 4780
Joined: 12/8/2001
From: Newberry, FL, USA
Status: offline
quote:

ORIGINAL: 13BRV3

Thanks Brian. That confirms everything I thought I knew about these cells. I don't understand Red's comments at all.

Cheers,
Rusty



My bad, I didn't expand the graph to see that A123 cells were being discussed. The deterioration in cycle life is more predominate in LiPo cells. In general, battery life is cut in half for every 10 degrees C above room temperature. This is true for Ni-Cd, Ni-Mh where separator deterioration is the primary failure mode. If there is a primary failure mode for A123 cells I have not heard what it is and how it is impacted by temperature.


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Red S.
AMA 951 Leader Member

(in reply to 13BRV3)
       Post #: 9

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