# LifePO4 Lifespan (not cycle life)



## natterjak (Nov 30, 2008)

Hi all,

Does anyone have any data on the lifespan of LiFePO4 batteries, by which I mean the retained capacity over time? Many manufacturers publish cycle life data showing that 2000 cycles, etc. are achieveable, but I'm specifically interested in the effect of time on the capacity. 

For example, if I only cycle my battery once a week, a 2000 cycle lifespan to 85% capacity will in theory last until 2046. I wouldn't mind betting though that capacity is lost year by year.

Does anyone have either manufactuer's data, theoretical predictions or real world experience? 

TIA.


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## favguy (May 2, 2008)

Well, I'm hoping we'll start to findout with replies to the above thread I just posted  I think the consensus is up to 10 years, but they haven't been about long enough yet for anyone to know very long term, but I doubt thay'll last anything like 38 years!! Would be nice though!


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## david85 (Nov 12, 2007)

I have seen a single projection of 10-15 years. But what you have to remember is that this stuff is still only about 6 years old so unlike cycle life, the shelf live cannot be confirmed until some of them start getting really old. What I am noticing is that manufacturers are starting to predict life spans that are a 6-7 years now that there are batteries out there that are lasting almost that long.

What I have yet to find however, is anyone that has a LiFePO4 battery that died for no reason. Eveyone that uses thunderskys for example seems to be very happy with them (there are other brands as well).


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## saab96 (Mar 19, 2008)

The line we're usually given is that lithium batteries HAVE to be made JIT because of shelf life issues, that they can not just be made en masse and sit in a warehouse. That doesn't sound like a 10 year lifespan to me.


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## natterjak (Nov 30, 2008)

But is that Lithium Polymer, Lithium Ion or LiFePO4?


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## david85 (Nov 12, 2007)

The general rule for the older lithium ion is 3-5 years for spiral cells and up to 10 years for high quality polymer cells.

LiFePO4 cells are available in spiral as well as polymer configuration as well. Being a more stable chemistry, they ""should"" last at least as long as lithium ion, since they already show better cycle life and less sensitivity to abuse.

All batteries are sold ASAP after manufacture no matter what the chemistry is. Its simply the standard of the battery industry.

Bottom line is theres no way to really know fos sure until you actually see batteries 10+ years old in service. It will be another few years for that.....


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## sailfish11 (Sep 15, 2007)

natterjak said:


> I wouldn't mind betting though that capacity is lost year by year.


I've heard (somewhere) that you should expect them to lose about 3% capacity/year. I've also talked to one Li-On user that said his pack had significant losses in the first year (~10%). But that was a few years ago and I think the technology (and QC) has improved significantly.


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