Cell imbalance on new pack
05-29-2006, 11:55 AM
#1
Senior Member
Thread Starter
My Feedback: (325)
Join Date: Mar 2003
Location: LaGrange, OH
Posts: 14,857
Likes: 0
Received 0 Likes
on
0 Posts
Cell imbalance on new pack
I am relatively new li-po user and have ran a half dozen 2S and 3S medium packs less than 100 runs. Here's what happened to my newest pack 3S x 1700 it sat for a month in the package. I must say that all my packs had been in perfect balance.
I checked the balance (after installing connector) and noticed about .2-.3 volts difference on 1 cell. I then charged on a very conservative li-ion setting and the other 2 cells wound up being 4.215 and 4.225 . I then discharged to a very conservative setting and only read 600-700 mah. The 1 low cell was dangerously low so I proceeded to manually balance the cells at various voltages.
The pack is now perfectly balanced and has 1 run on it with them staying perfectly in balance. The manufacturer claims it will stay that way and the cells are arranged and assembled by IR and discharg capacity. I believe them. I also wonder how this one got lower though?
Anyways I just thought I would post to inform to check balance on a new pack, I always will now, yet some of mine went into service without checking for a few cycles. I also had another brand new one that set for a month and it is perfect. go figure,,
I checked the balance (after installing connector) and noticed about .2-.3 volts difference on 1 cell. I then charged on a very conservative li-ion setting and the other 2 cells wound up being 4.215 and 4.225 . I then discharged to a very conservative setting and only read 600-700 mah. The 1 low cell was dangerously low so I proceeded to manually balance the cells at various voltages.
The pack is now perfectly balanced and has 1 run on it with them staying perfectly in balance. The manufacturer claims it will stay that way and the cells are arranged and assembled by IR and discharg capacity. I believe them. I also wonder how this one got lower though?
Anyways I just thought I would post to inform to check balance on a new pack, I always will now, yet some of mine went into service without checking for a few cycles. I also had another brand new one that set for a month and it is perfect. go figure,,
05-29-2006, 06:58 PM
#2
Banned
My Feedback: (9)
Join Date: Dec 2001
Location: Newberry, FL
Posts: 5,925
Likes: 0
Received 0 Likes
on
0 Posts
RE: Cell imbalance on new pack
I'm laughing! 
Your statement, "The manufacturer claims it will stay that way and the cells are arranged and assembled by IR and discharge capacity."
I doubt if you talked with the manufacturer. You talked with the distributor, most of which have difficulty determining + from -. If you recall the incident where a new pack from a leading distributor had these reversed. These are the people that make 20C continuous and 30C burst claims without a clue as to what that means.
Most packs I have seen are pretty well balanced as received, no credit to the distributor however. It is just the nature of the cells as manufactured, only some mishap in the process of shipping or assembling the packs might lead to significant unbalance. Therefore it is a good idea to check new packs for balance before using.
Your statement, "The manufacturer claims it will stay that way and the cells are arranged and assembled by IR and discharge capacity."
I doubt if you talked with the manufacturer. You talked with the distributor, most of which have difficulty determining + from -. If you recall the incident where a new pack from a leading distributor had these reversed. These are the people that make 20C continuous and 30C burst claims without a clue as to what that means.
Most packs I have seen are pretty well balanced as received, no credit to the distributor however. It is just the nature of the cells as manufactured, only some mishap in the process of shipping or assembling the packs might lead to significant unbalance. Therefore it is a good idea to check new packs for balance before using.
05-29-2006, 07:21 PM
#3
Senior Member
Thread Starter
My Feedback: (325)
Join Date: Mar 2003
Location: LaGrange, OH
Posts: 14,857
Likes: 0
Received 0 Likes
on
0 Posts
RE: Cell imbalance on new pack
Yes it was the dealer/distributor, so far he is right. Which part is funny?
I was told that the cells are matched for IR and discharge by a computer "to a very low tolerance"
I have heard of this before, but seems to be in the back ground of lipo packs.
I am wondering if effort is being made on lipos like a nimh battery matchers are doing. I would be surprised if the cells I have are random. I did not press the issue or ask any more question like the tolerance. Possibly you know if this is happening at the manufacturer. They are dualsky cells I think.
I was told that the cells are matched for IR and discharge by a computer "to a very low tolerance"
I have heard of this before, but seems to be in the back ground of lipo packs.
I am wondering if effort is being made on lipos like a nimh battery matchers are doing. I would be surprised if the cells I have are random. I did not press the issue or ask any more question like the tolerance. Possibly you know if this is happening at the manufacturer. They are dualsky cells I think.
