# LiFePo4 life tests



## MN Driver (Sep 29, 2009)

One more detail you didn't mention was what rates you were charging and discharging at. If you discharge a cell at a high rate, it can make a difference too. I'm not sure how much of a difference we will see with the A123 cells since they are designed to have heavy draws but I know the FMA independent tests made them looking like you could really cut the life short if you discharge at a high rate with them, even if below their continuous 70A rating.


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## _GonZo_ (Mar 23, 2009)

> In order to get quick results I think will use around 1C charge and 2C discahrge with no wait time between charges discharges (may be a litte wait time is need to cool after discharge, but do not think so A123 cells are very powerfull and do not heat up much at 2C discharge, will see)


Both cells will be done at the same rates so I think will not make difference between them.
And yes obviously higher rate shorten life of any battery.


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## JRP3 (Mar 7, 2008)

What's the max voltage for A123 cells? You may need to go a little higher than 3.7 to see a difference.


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## _GonZo_ (Mar 23, 2009)

The idea is not overcharge the cell just to compare if partial cycles are better, same or diference irrelevant in LiFePo4 batteries life spam.

As per A123 the charging is finished at 3,6V
By experience a little bit more is need, like 3,7V is OK for South Spain winter.
Maximun voltage before ruining the battery is 4,2V

Atached Specifications PDF


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## MN Driver (Sep 29, 2009)

This specsheet is different than the ones I've seen for these A123 M1 cells in the past. It's interesting to note the below 0 degree C charge and cut-off voltages at 4.2 volts to 0.5 volts. I would have figured that going before 2 volts at any temperature would be best avoided. I wonder what temperature and rate it would take to pull them down to 0.5 volts and how much capacity there really is below two volts at a low temperature. That is some insane voltage sag if there is much down there at a modest rate.


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## _GonZo_ (Mar 23, 2009)

We made some time ago back up sistems to work in the North Pole and we performed tests of the A123 cells under low temperatures. And they actually work very well.

You can see attached a comparation chart me made of a discharge at normal temperture (22ºC) and at low temperature (-21ºC) of a cell of this type. Both at 3A current draw.


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## _GonZo_ (Mar 23, 2009)

I just received an interesting info about the new prismatic cells of A123, and in one of the pages comes out info about Cycles life, and for what the grafic says they are getting over 100,000 (yes 100,000) cycles at 50% capacity usage.
So I think it is interesting now more than ever to know about the differences of using full or patial cicles on LiFePo4 cells.

As I am on the testing mode now I will start testing today.

I attach the PDF from A123.


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## JRP3 (Mar 7, 2008)

Those cells will outlive us


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## _GonZo_ (Mar 23, 2009)

JRP3 said:


> Those cells will outlive us


I am putting all info about those cells toguether so I will make a post about them.
The problem is that I have received some overall info from A123 and some more detailed from other 3rd parties and part of it may be confidential so I have to be very carefull. I am just waiting for confirmation from A123.

One thing I can tell you is that they will be available very soon. Preorders will be a question of days.


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## _GonZo_ (Mar 23, 2009)

I just started today the test on the LiFePO4 cells (A123)
I picked up two new cells (cell 1 & cell 2) and charge and made first discharging curves for record.

I decided to set the values as:

Cell 1 (this one will make full cycles)
Charge: 3A - 3,7V
Discharge: 6A - 2V

Cell 2 (this one will make partial cicles)
Charge: 3A - 3,5V
Discharge: 6A - 2,9V

I started Cycling the cell 1 on first cycle it gived 6,72Wh


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