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Oct 24, 2006, 09:57 PM
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What is the capacity for those cell?

~asm
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Oct 24, 2006, 10:34 PM
Use the Force!
LBMiller5's Avatar
Thanks for all the good words guys! It really means a lot to me to see people get value out of the efforts that I make.

The specifications for these cells are as follows (From the A123 Spec Sheet):






Here is the dimensional drawing for the individual cells.






Here is the discharge graph of the cells at 1 Amp (0.43 C), 10 Amps (4.3 C), 30 amps (13.0 C) and 40 Amps (17.4 C).






And finally, here is the output performance with respect to temperature at 25 C (77 F), 0 C (32 F) and -20 C (-4 F).






Hopefully that will answer all your questions. If you have any more comments or questions, let me know.

Lucien
Last edited by LBMiller5; Oct 25, 2006 at 05:58 PM.
Oct 24, 2006, 11:19 PM
Fly it like you stole it..
Tram's Avatar
Nicely done..
Oct 25, 2006, 12:16 AM
Registered User
Thanks Lucien!

The pic's along with the descriptions make it too easy!

And thanks Charles for the dremel idea. If I can't find a Torx I'll go that route.
Oct 25, 2006, 12:27 AM
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LBMiller5's Avatar
Tonight I went ahead and modified my T-10 Torx bit to fit down into the deep holes without having to drill them out. I chucked the bit up in my drill and spun it while I used a cut-off wheel in my Dremel tool to grind down the bit. Here is what it looked like when I was done.





Now it drops right down into the hole and makes perfect contact with the screw heads. Looks like I am ready to take apart pack #2!

Good luck guys!

Lucien
Oct 25, 2006, 06:24 AM
Registered User
Good to see that cold temps, 32f at least, don't really affect these cells. I figured that if they're gonna be used by contractors and such that they'd work okay in the cold, but I had not seen the data.
Oct 25, 2006, 06:45 AM
Southern Pride
everydayflyer's Avatar
They do well cool but much better warm.


https://www.rcgroups.com/forums/atta...mentid=1010357

Charles
Oct 25, 2006, 08:18 AM
Registered User
how many amps do you think the original assembly can stand.
I would like to make 10s packs and would like to use the original wieled bars to save time making tha packs. Is 85-100amps peak possible if I reinforce the fusible bar?
Oct 25, 2006, 11:38 AM
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LBMiller5's Avatar
Pitounet,

With the exception of that one necked down buss bar, I would say that the pack could do 100 amp peaks, but for no more than 15 seconds at a time. The max spec for the cells is 120 amps for 10 seconds, so 100 amps for 15 seconds or 85 amps for 20 seconds would be achievable.

To reinforce the one buss bar, I would quickly tin 2 areas on the buss bar on either side of the cut down area. Aftert letting the cells set until they are cool to the touch, I would then take a short length of tinned 12 or 14 gauge wire about 1/2" long and reflow the solder to add it in to the buss bar. That would bring the cross sectional area back up to match the other buss bars.

You will want to use a large soldering iron to do this (40 watt or larger) and get it and out in less than 2 seconds to avoid overheating the cells. With that mod, the pack could be used as-is and you would simply need to tape it up to insulate the cell end caps.

If you plan on pulling that kind of current, I would use double leads of 12 gauge wire running out to your connector.

Lucien
Last edited by LBMiller5; Oct 25, 2006 at 09:12 PM.
Oct 25, 2006, 11:43 AM
Registered User
Since these are Li-ion, not Lipo. so, what is the "hot off the charger" voltage?

~asm
Oct 25, 2006, 01:09 PM
Registered User
Quote:
Originally Posted by LBMiller5
Thanks for all the good words guys! It really means a lot to me to se people get value out of the efforts that I make.... Here is the discharge graph of the cells at 1 Amp (0.43 C), 10 Amps (4.3 C), 30 amps (13.0 C) and 40 Amps (17.4 C).



And finally, here is the output performance with respect to temperature at 25 C (77 F), 0 C (32 F) and -20 C (-4 F).



Hopefully that will answer all your questions. If you have any more comments or questions, let me know.

Lucien
My thanks also, Lucien.

Your temperature dependent graphs saved me alot of work - I was going to do some. Also, your detailed look inside the DeWalt packs helps me plan my use of the bus bar arrangement for pre-planning my derivative packs (my DeWalts will arrive any day now).

For various other discgarge rates, temperature rise @ those rates, various charging rates, burst performance, degradation, etc:

https://www.rcgroups.com/forums/show...98&postcount=1
https://www.rcgroups.com/forums/show...9&postcount=21
https://www.rcgroups.com/forums/show...0&postcount=27
https://www.rcgroups.com/forums/show...9&postcount=38
https://www.rcgroups.com/forums/show...8&postcount=58
https://www.rcgroups.com/forums/show...6&postcount=59

- RD
Oct 25, 2006, 05:00 PM
Registered User
Great job on documention for A123s! Let me just add that T-10 is available on the end of a screwdriver. I think I got mine at Sears.

And that fuse link gets HOT! at 70A. I solder copper braid over the link for 10s packs.

And finally. These cells as noted above are very temperature dependent. If you prop for 40A when the cells are cold, you'll find in a few moments, you'll be pulling 50A... I don't let air cool my cells in flight.
Oct 25, 2006, 05:40 PM
Registered User
Thanks Lucien, great photos (from obviously a nice camera) and a nice write-up. I have a pack on its way to the North country from an Ebay "buy it now at $90." I will try 4S packs in the MEC tubes that Pete supplies....now to get a Lipodapter..!

Bill
Oct 25, 2006, 08:28 PM
Registered User
A follow up to this would be to show a "balance connector" being added to a pack...hint hint..!

Bill


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