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Old 04-08-2009, 08:43 AM
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Jimdear2 Jimdear2 is offline
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Default Purchase LiFePo cells over an extended period?

Since I am on a budget like a lot of people, but want LiPo for my project. This creates a delema.

I specifically want A123 or equivalent cells because my project requires short high amp draws. I have been wondering about the advisability of purchasing a few cells (as money or deals became available) at a time over an extended period.

This would keep food in my belly and would also allow time to build the packs in between purcheses.

What is the concensus feeling about this.

I'm concerned about shelf life because this kind of purchase might take a year or more. I have read many pros and cons on this site but have never seen a real concensus.

The alternative of saving up to buy is of course available but a lump purchase makes me miss those deals where just a few cells are available.

Borrowing (I have no credit because I haven't borrowed in 30 years) is out of the question.

Your thoughts will be welcomed.
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Last edited by Jimdear2; 04-08-2009 at 04:12 PM.
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Old 04-09-2009, 02:29 PM
bblocher bblocher is offline
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Default Re: Purchase LiFePo cells over an extended period?

Quote:
Originally Posted by Jimdear2 View Post
Since I am on a budget like a lot of people, but want LiPo for my project. This creates a delema.

I specifically want A123 or equivalent cells because my project requires short high amp draws. I have been wondering about the advisability of purchasing a few cells (as money or deals became available) at a time over an extended period.

This would keep food in my belly and would also allow time to build the packs in between purcheses.

What is the concensus feeling about this.

I'm concerned about shelf life because this kind of purchase might take a year or more. I have read many pros and cons on this site but have never seen a real concensus.

The alternative of saving up to buy is of course available but a lump purchase makes me miss those deals where just a few cells are available.

Borrowing (I have no credit because I haven't borrowed in 30 years) is out of the question.

Your thoughts will be welcomed.
The only thing I can think of that you didn't mention is what happens to the technology and more importantly the cost over time. If you're thinking a year or more before you have enough to purchase all the cells, I'd wait. Chances are you'll be able to buy the whole setup for cheaper as prices continue to fall.
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Old 04-09-2009, 02:39 PM
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Default Re: Purchase LiPo cell over ectended period?

Jim,

have you seen this article comparing cost and quality of different cylindrical cells?

http://zeva.com.au/tech/LiFePO4.php

My point is that A123 is not the only game in town, you may find other brands more affordable and still acceptable quality for your needs. And like Brian said, this market is growing, mostly by Asian manufacturers unfortunately, but competition is competition, the price is bound to fall once market begins to saturate.

Hope this helps.
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Old 04-11-2009, 05:22 PM
AndyH AndyH is offline
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Default Re: Purchase LiPo cell over ectended period?

Jim,

What level of performance do you need? When will you need the cells?

There is a range of price/performance between A123-systems and Thunder Sky, some of which are covered in Dimitri's post, some not.

Andy
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Old 04-11-2009, 07:15 PM
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Jimdear2 Jimdear2 is offline
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Default Re: Purchase LifePo4 cells over an extended period?

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Originally Posted by AndyH View Post
Jim,

What level of performance do you need? When will you need the cells?

There is a range of price/performance between A123-systems and Thunder Sky, some of which are covered in Dimitri's post, some not.

Andy
Andy,

Actually I am very intersted in a larger spiral battery that has threaded studs and use interlocking plastic blocks to allow packs of different configuratuion to be built.

Right now I am starting my projects out at a lower level to prove the concept without breaking too many things.

What I am doing is converting one of my ultralight pulling tractors from ICE to Electric (to 72 volt 450 amp controller). I am also doing a conversion of a older Cub Cadet Garden tractor (to 48 volt 450 amps) which I will use as a utility vehicle at the track and on the farm. I will also pull with it. Both will have basically off the shelf motors.

I am currently going to be using AGM batteries in both tractors becaise of the available 10-15C or so discharge rate (also, although they are used but were also free). I have three strings of six 16ah Hawker Odysseys for the ultrlight and one string of 4 High Rate 41ah UPS batteries for the garden tractor.

Eventually I want to go to higher voltages and amprages for both and more watt hours for the garden tractor. The AGMs have me pretty much maxed me out for weight so I will need to go to LiFePO4 to get the performance I want.

I was planing, per my question, on trying to collect he necessary cells to eventually double the voltage on the ultra light and go to 72 volts on the garden tractor over the next year. I would most probably try to duplicate the existing battery packs with LiFePO4 to close out this year if I could afford the cost of a total changeover (chargers, BMS etc) otherwise I would go for next season with a ramp up of voltage till things start to break.

Enough rambling. It looks like the general feeling is . . . I'm better off waiting, not so much because of battery storage problems but for cost advantages of a single large purchase.

I would still like to get an answer about buying over an extended period. Storing them untill suffucient batteries are procured to build the packs needed.
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Old 04-11-2009, 07:34 PM
Voltswagen Voltswagen is offline
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Default Re: Purchase LiPo cell over ectended period?

Dear Jim (sorry I couldn't resist)
I'm going to postpone my LiFePo purchase for one year or so.
Here is my logic:
The American Dollar is on it's ass making foreign purchases of Lithium very pricey. In a year or so, because of.....or despite Obama's Stimulus Plan, the American Economy should be in recovery. If it does this will result in a stronger Dollar and better foreign Lithium prices (the conversion rate does matter to them).
If the economy doesn't recover then I can spend my Lithium money on
Rice, Beans and Bullets.
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Old 04-11-2009, 07:37 PM
martymcfly martymcfly is offline
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Default Re: Purchase LiPo cell over ectended period?

If I were to do something like this, about when you have half of your LiPo's, they would change the style and make the new ones not compatable with what I had or something like that.
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Old 04-18-2009, 06:05 PM
AndyH AndyH is offline
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Default Re: Purchase LifePo4 cells over an extended period?

Quote:
Originally Posted by Jimdear2 View Post
Actually I am very intersted in a larger spiral battery that has threaded studs and use interlocking plastic blocks to allow packs of different configuratuion to be built.
Something in a 40138 size? Sounds familiar.

Overall, LiFePO4 are still pretty new, and I don't know of any that have been on the shelf for 5 years. But they generally have a very low self discharge (2-3% per month) and can sit for a long time. The 40138 cylindrical cells have aluminum cases and one aluminum terminal, so you'll want to keep them dry.

Companies are finding ways to get more capacity into the same sized cell, so if you got 10Ah cells now, you might have 12 or 14Ah cells later.

Andy
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