LiFePO4 Questions [AA sized]

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kenzo

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Hello guys. I've been doing some reading on this type of cell cause I want higher output with my lights (as we all do :whistle:) but don't really want to use the other lithium chemistry (seems to be too much maintenance for me).

This is the setup i'm planning to use:
http://www.dealextreme.com/details.dx/sku.1236 [ The Charger ]
http://www.dealextreme.com/details.dx/sku.5109 [ Batteries ]

Holder for batteries (which i found in my desk ._. ) will probably connect with clips?
img0603ei0.jpg



The LiFePO4 seem safer, but i still have a few questions about them (really not prepared to deal with protected/unprotected lithium).

1 - Is my planned setup ok (i.e. charger ~ batteries ~ connecting the holder to the charger with clips).
2 - Are LiFePO4 safe (i.e. explosion prone).
3 - I understand that Li-ion should be stored at a certain voltage? ( cant remember exact voltage ). But do LiFePO4 need this type of care? or can i leave them fully charged to be ready for use.
4 - How long can i leave them fully charged for use?
5 - Anything important i need to know before using these? :D


Thanks guys. (been reading CPF everyday but havent really posted anything :p)
 
kenzo said:
1 - Is my planned setup ok (i.e. charger ~ batteries ~ connecting the holder to the charger with clips).
2 - Are LiFePO4 safe (i.e. explosion prone).
3 - I understand that Li-ion should be stored at a certain voltage? ( cant remember exact voltage ). But do LiFePO4 need this type of care? or can i leave them fully charged to be ready for use.
4 - How long can i leave them fully charged for use?
5 - Anything important i need to know before using these? :D
Click to expand...

LiFePO4 batteries are very interesting to me but I tend to think of them as larger cells with protection curcuits built into the pack. Here is the pros/cons with LiFePO4

Pros
They won't explode
They last many more cycles than lithium-ion (cobalt type)
They have a much, much longer shelf life than Li-ion/NiMH
They can take very high discharge rates (the bigger cells do)
They are normally rated at 3.2V which works great in flashlights.
They eventually will be cheaper than 3.6V lithium-ion cells
They like to run at warm temperatures
Can be made very environmentally friendly
They won't explode

Cons
They have lower capacity than 3.6V lithium-ion
They don't like to be discharged below 2.2V
Good luck finding a protected cell in "normal" AA/CR123 sizes :(

I was reading about 4C testing on PHET LiFePO4 3.2V 10AH cells. Yes, charging and discharging at 40 amps! :D So far, the packs have hit 2,000 cycles without any major loss in capacity and will continue to 10,000 cycles. Now if PHET rolls out a CR123 or AA/AAA sized cell with a protection curcuit... I am buying them as fast as I can type the numbers on my keyboard. I dream of a 25.6V 42AH pack for my electric bicycle project.

Just because there are some really good companies making LiFePO4 cells does not mean they are all good. The technology is getting there and PHET is rolling out some serious stuff in March. I don't know the sizes but if they are 18650, 14500 or RCR123A sizes...I am going to post the link.
 
/agree with everything BentHead said.... cept one little thing... :)

you aren't going to find many LiFeP04 cells with protection, it's not necessary, they are nearly as tolerant to over charging and over discharging as NIMH, and they will never vent with flame from abuse, no need for protection here. I'd rather have as much of the cell size dedicated to capacity on this chemistry than a PCB.
 
Thanks for the input guys :D
But, can i leave this type of battery charged like a nimh? And also, would simply connecting the battery-holder (AA sized) i have to the charger with clips be ok?
 
Somebody agrees with me! :D
A simple low voltage shutoff won't take up too much space so it is something I'd like to see. Charge LiFePO4 then remove it from the charger just like any lithium-ion or NiMH cell. Make sure the charger shuts off when the cell is fully charged and won't "trickle" charge.
A123 Systems has a 18650 cell that is coming available, 15 to 30 amps from the cell anyone? I use those cells in my DeWalt "36V" (actually around 32V or so) drill/saw system and they are amazing.
 
Thanks for the link,
I don't have a use for 18650 cells at this time but when I do, it is A123 or PHET to feed them. 1774 cycles to 80% of capacity with a 2C charge/4C discharge? Not to hard to figure out those cells will do the trick.
 
mdocod said:
you aren't going to find many LiFeP04 cells with protection, it's not necessary, they are nearly as tolerant to over charging and over discharging as NIMH, and they will never vent with flame from abuse, no need for protection here. I'd rather have as much of the cell size dedicated to capacity on this chemistry than a PCB.
Click to expand...
Actually, people testing A123/LiFe cells on rcgroups have found they too die if overdischarged, but only if left overdischarged for a whlie, IIRC.
In other words: overdischarging them isn't a surefire way to kill them as with LiIons, but they still don't like it, and so would probably benefit from a low voltage cutoff circuit.
 
So.... does this particular combo then work for charging LiFePO4 batteries?

Have you moved up to 18650's?
 
This is the setup i'm planning to use:
http://www.dealextreme.com/details.dx/sku.1236 [ The Charger ]
http://www.dealextreme.com/details.dx/sku.5109 [ Batteries ]
Click to expand...

Somebody on this board has already done that exact thing. I couldn't find the thread though.

I am also planning on doing the exact same thing to use in my L1Tv2.0. I would say that you lose temperature protection for obvious reasons, but I'm not 100% sure that charger has temp. protection to begin with.

I should have it all together by next week, I'll let you know how it works out.
 
I got the charger and LiFePo4's in a few days ago. This setup seems to work just fine:
IMG_2528.jpg


This is the ultrafire 138 charger bought from 4sevens and 2 LiFePo4 14500 batteries bought from KD. The charger has the 3.6v/3.0v selector switch (set for 3.0v for these). The 14500's are labeled as 1600ma, which I don't believe to be true. The battery holders are form Radio Shack with a couple of cut dowels and push pins soldered to the holder wires.

I ran each of the batteries in my L1Tv2.0 rb80 on high until it reached the same output as low. I got about 24 mins for each battery. After immediately pulling out the batteries, they were about 1.8v and climbing to above 2.2v in less than 1 minute. Even hot off the charger, the low mode works fine. I won't be doing any runtimes on low however.

Overall I am happy with them. They give me a good output (noticeable from NIMH) for not very long runtime however. I have noticed that my L1T runs a little on the short side even on eneloops (about 1:40 on high).
 
kenzo said:
Hello guys. I've been doing some reading on this type of cell cause I want higher output with my lights (as we all do :whistle:) but don't really want to use the other lithium chemistry (seems to be too much maintenance for me).

This is the setup i'm planning to use:
http://www.dealextreme.com/details.dx/sku.1236 [ The Charger ]
http://www.dealextreme.com/details.dx/sku.5109 [ Batteries ]
anything :p)
Click to expand...

Without refering to my cheat sheet, are these AA size? If so, why is energy density so poor?
 
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