direct soldering A123 developer kit cells  
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direct soldering A123 developer kit cells - 11/22/2006 5:38:42 AM   
zeropointbug


 

Posts: 7
Joined: 11/22/2006
From: tisdale, SK, CANADA
Status: offline 		Hi Brian,

This July i bought the A123 Systems developer kits (2), and made a 5s2p pack to run a 600 watt dual DeWalt 820 (current monsters!) motors 1/8 buggy; and with GREAT results! I had 12 IB3600 cells, and they fried after one season of bashing use. These M1 cells only get warm! The runtime is awesome too, with about 10 minutes at full throttle speed runs, and it's 100% right until they dump, its great! However i had to make a big bulky battery back from formed Lexan to hold the cells with weak tabs on the developer cells.

Anyways, i am converting the car to run a Feigao 540C-7XL motor, the new Quark Monster 125B S/C, this setup with 16.5 volts (5s2p) should be able to punch out 1200 watts with 15 minute runtime, and 70mph top speed (if geared right).

ANyways!, to get to the point, i am very experienced with soldering. Could I direct solder RC copper bars to the cells with a high powered iron (250w) to quickly solder the connection and then using a heatsink quickly cool it down? Otherwise I have no room because of the bulky 'dual tabs' of the developer cells, and they are simply too weak and rigidless to work for me.

So if you could reply ASAP, great!

THanks!

zeropointbug
       Post #: 1

RE: direct soldering A123 developer kit cells - 11/22/2006 6:42:04 PM   
A123 Racing


 

Posts: 101
Joined: 8/25/2006
From: Hopkinton, MA, USA
Status: offline 		Hello zeropoint,

Thanks for your questions. The cells you purchased were the first developer kit cells that we sold when we first began selling the batteries. Now we offer loose cells for the RC community that have smaller tabs which are easier to work with and create a stronger mechanical bond.

Unfortunately you should not solder direct to the cells. The heat from the soldering iron will damage the electrolyte inside the battery. There are reports of people soldering to the cell with no repercussions. The damage done to the cell when soldered will result in shorter life cycles than we are advertising, which is why people that have soldered to the cells are claiming that there are no negative effects. They will not get the same pack life as someone who purchased a pack or properly soldered the pack together with the tabs we offer.

Hope this helps, please let me know if you have any other questions.

Brian



(in reply to zeropointbug)
       Post #: 2

RE: direct soldering A123 developer kit cells - 11/22/2006 6:43:35 PM   
everydayflyer



Posts: 854
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		A123 says to never solder directly to the cells. This is the standard position taken by all cell manufactures. I have soldered to them and so have others.
Here is a good write up.

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

Charles

(in reply to zeropointbug)
       Post #: 3

RE: direct soldering A123 developer kit cells - 11/22/2006 8:31:03 PM   
zeropointbug


 

Posts: 7
Joined: 11/22/2006
From: tisdale, SK, CANADA
Status: offline 		Thanks Brian

EveryDayFlyer:

I did read that article about the DeWalt pack rebuild. However, they did a silly smack-on solder joint which takes more thermal heating of the cell, that will surely damage the cell.

I am sure i can very quickly solder the batt bars on, and using a heatsink very quickly cool it down before any real long term damage can occur. As i said before, high power iron is key to this, 250watt iron. I could even use that automotive copper wire (its exposed), as it would mold around the solder and might really grad the heat away quickly.

But lets say, if i were to minimize the (or even prevent damage) to the cell; what kind of cycle life decrease are we talking about here? Say i were to get 1000+ cycles not soldering the cells, as thats what they are rated at +.... do you know what the decrease in cycles i should expect if I solder the cells, say in the best case scenario?

Thanks Brian!

zeropointbug

(in reply to everydayflyer)
       Post #: 4

RE: direct soldering A123 developer kit cells - 11/22/2006 9:20:34 PM   
everydayflyer



Posts: 854
Joined: 8/21/2005
From: Buchanan, GA, USA
Status: offline 		Well as one who has followed A123 post for over six month on RC Groups I have not read of anyone who has reached 1000 cycles as yet. The cells are still new in the RC Community.

I have not seen any practical life cycle test either. IMO lab test of cells and in the field use of cells are very different.

I am not disputing the data published by A123 Racing no more than I am disputing the data posted by PolyQuest, Kokam and others claiming 500 cycles with thier LiPolys.

My feeling are that A123 cells are very good and if I get 200 plus cycles in the applications which I am using them they they are a great buy.


Here is a post here with Graph of a 3cell pack of mine. This pack built using A123 Racing Developers kit and soldering was to their tabs only. The pack only has 25 cycles on it and I am very happy with its' performance but the jury is still out on how long it will really last.


http://www.rcuniverse.com/forum/m_5024587/anchors_5024587/mpage_1/key_/anchor/tm.htm#5024587

Charles

< Message edited by everydayflyer -- 11/22/2006 9:45:21 PM >

(in reply to zeropointbug)
       Post #: 5

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