[EVDL List]

LiFePo4 has the best cycle life if SOC is kept during use between 40% and
80%. To state the obvious taking a cell to zero volts is completely out of
the ideal range for capacity and cycle life performance.

I would not expect a cell taken down to zero volts would not have some
effect at least on cycle life. Just cycling a cell its useable full capacity
per A123 will give you less cycle life. Example a 1C load at 25 deg C at
1000 cycles cell will have 95% of its capacity. While this is a small loss of
capacity it is a loss. At 45 deg C the capacity loss is more then double the
lower temperature.

The A123 cells will hold their voltage for years if stored properly. I
have not read the voltage lately but 5 years with very little voltage change
when stored in a cool environment. An equal number of cells over 3000 in
number were kept under warmer conditions and they started losing voltage at a
very concerning rate. Out of 10,000 cells bought directly from A123 about
1% in two years started to drop in voltage. These cells although very
useable showed there is slight differences between cells manufactured at the
same time. So as good as A123 cells are there are slight random variations in
a small percentage.

So my point is if stored correctly your not going to take a cell voltage
down anytime soon unless under a load. If a cell is under a load then it
should affect capacity and cycle life. If just done once maybe it will not be
very significant under a very small load but done ten times or one hundred
times might have different results. Down to zero volts with any type of
load and have no loss in capacity or cycle life? I would not be betting any
money on that over the life of the cell this would not make a difference.

At best it might be slight but I would expect with a large enough sample
testing should show a loss. The main reason I believe this is battery
manufacturers test their products to their limits. If a cell was capable of this
type of performance with no damage it would not have gone unnoticed.

Although I am a fan of A123 cells I would have to agree with Lee. Don't
assume anything unless you test and measure and with a large enough sample to
account for random differences that occur in manufacturing. It does not
matter what chemistry of battery the only way to know is to verify with
testing.

Don Blazer


In a message dated 7/4/2012 12:01:27 P.M. Pacific Daylight Time,
xxx@xxx.xxx.edu writes:

Message: 3
Date: Wed, 04 Jul 2012 00:45:18 -0500
From: Lee Hart <xxx@xxx.xxx>
Subject: Re: [EVDL] A123 ALM 12V7 Batteries now charging
To: Electric Vehicle Discussion List <xxx@xxx.xxx.edu>

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