I killed a 1100mah pack (Full Version)

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GhostRider32 -> I killed a 1100mah pack (12/31/2007 1:55:47 AM)

Hey all,

I made a receiver pack from a VPX pack a few days ago and all was good until I left the plane on last night. This morning when I realized it I checked the voltage and it was 3.0v for the pack. I tried to recharge it but my Hyperion 0610I wouldn't even regognize it as a 2 cell pack. It kept saying 1 cell. Anyway, to get the pack to charge on the A123 setting I first had to charge it as a 4.8v 600ma nicad just to raise the voltage so the Hyperion would recognize it as a 2 cell pack. I got the voltage up to about 5.5v on the nicad setting and then switched the pack to the A123 charge. On the 3 amp A123 charge rate the pack got warm enough that the fuselage on the other side of the pack was warm. Evidently a cell shorted or something as now the pack reads 1.5v. I was under the impression that these cells were more durable than that so I'm wondering if I got a defective/weak cell or what? Any possibilities come to mind?



powerslider -> RE: I killed a 1100mah pack (12/31/2007 2:10:48 AM)

Try a trickle charge for several hours, I think you need to try to bring them back slowly when they are discharged to far....



everydayflyer -> RE: I killed a 1100mah pack (12/31/2007 3:59:13 AM)

quote:

I made a receiver pack from a VPX pack a few days ago and all was good until I left the plane on last night. This morning when I realized it I checked the voltage and it was 3.0v for the pack.


First question that comes to mind is what was the voltage of each cell and I realize you have no idea.

I would have removed the pack and checked each cells voltage first. These cells are very durable but they can not tolerate being discharged to zero nad left setting and they can not stand be reversed charged if one cell goes to zero and you just go ahead and charge the pack as if nothing is wrong.

This could very well have been one of the cases where balancing leads and balance charging could have saved the pack.


Charles



GhostRider32 -> RE: I killed a 1100mah pack (12/31/2007 4:28:31 AM)

You are correct, I used my Fluke to measure the entire pack and not the individual cells. Next time I will put a balance tab on the cells.



GhostRider32 -> RE: I killed a 1100mah pack (1/1/2008 12:40:39 AM)

Well,

Finally ordered some balance tabs for 2,3 and 4 cell packs. Maybe I can keep from destroying another pack. :)



dirtybird -> RE: I killed a 1100mah pack (1/3/2008 3:10:30 PM)

I found two other ways to kill those cells.
1) Charge with too high voltage.
2) Solder to a tab on the cell without a good heat sink.



everydayflyer -> RE: I killed a 1100mah pack (1/3/2008 3:29:21 PM)

quote:

Solder to a tab on the cell without a good heat sink.


I find that it is not so much what you solder but rather how you solder it.

I never use a heat sink on these are their big brothers.

I have assembled 4 ea. 4S packs from the VPX packs. I have soldered 14 ga. leads directly to a single cell (used for CBA testing) and I have soldered 14 ga. solid copper wire directly to the taps (center of cells)to eliminate some of the high resistance caused by the factory straps.

All 4 packs are doing just fine even the one that I am abusing the YNW out of with 10A charges and 8A discharge cycles during one of which the pack reached 1.32 volts (0.33V cell average).


I should add that the VPX cells really do have extremely small tabs not suitable for soldering by those with mininum soldering skills.

There is a logical / valid reason why all battery manufactures clearly state not to solder directly to the cells. Yes we do it all the time and have for many years but we have been warned not to.
Charles



dirtybird -> RE: I killed a 1100mah pack (1/3/2008 8:21:13 PM)

When I soldered to the cell without the heat sink I found a 2in orange flame shooting out the other end.
You are free to do what you like but I solder to the pigtails. Its safer.



everydayflyer -> RE: I killed a 1100mah pack (1/4/2008 4:24:38 AM)

quote:

You are free to do what you like


Thank you , I usually do as long as it is legal.


Charles



coro_sk -> RE: I killed a 1100mah pack (1/4/2008 1:25:48 PM)


quote:

ORIGINAL: dirtybird

When I soldered to the cell without the heat sink I found a 2in orange flame shooting out the other end.
You are free to do what you like but I solder to the pigtails. Its safer.


I feel much safer with well soldered wires, to power receiver or ESC with BEC, especially with fast flying plane above my head.

You are free to do what you like, but small 1100mAh A123 can be soldered with absolutely no problem in a split of a second, cell remain completely cold.



dirtybird -> RE: I killed a 1100mah pack (1/4/2008 2:36:29 PM)


quote:

ORIGINAL: coro_sk


quote:

ORIGINAL: dirtybird

When I soldered to the cell without the heat sink I found a 2in orange flame shooting out the other end.
You are free to do what you like but I solder to the pigtails. Its safer.


I feel much safer with well soldered wires, to power receiver or ESC with BEC, especially with fast flying plane above my head.

You are free to do what you like, but small 1100mAh A123 can be soldered with absolutely no problem in a split of a second, cell remain completely cold.


The cell I soldered to was completely cold, too - Except on the end where the flame was shooting out.
You have to get the temperature high enough to melt the solder. Even though the cell might not rupture, you have probably damaged the cell. You will never know.



RTK -> RE: I killed a 1100mah pack (1/29/2008 4:55:17 AM)


quote:

ORIGINAL: dirtybird


The cell I soldered to was completely cold, too - Except on the end where the flame was shooting out.



[:)][:)][:)]Now that put a smile on my face today.



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