LiFeP04 3V why only 500mA capacity? more

[marinemaster]

Hi,

I want to use 3V rechargeable LiFeP04 NOT 3.6 or 3.7
However they are only 500mA which means short runtime. So is there or will there be a higher runtime or mA offered. Any ideas?

Chris

 

[Fallingwater]

LiFe appears to be the future of lithium rechargeable cells, so yeah, it's very likely that there will eventually be cells with considerably higher capacity. Don't hold your breath though... for the time being if you want LiFe you deal with the lower capacity, and there's nothing you can do about it.

 

[Alan B]

Each chemistry has its energy density characteristics. Turns out LeFePO4 has lower energy density than many other Lithium chemistries. However the extremely important increased safety makes it worthwhile in spite of this. The automotive industry is working on high current cells, and will also be interested in capacity, so we may see some improvement, but this will take time. The real question on capacity is how much does one need. If you recharge frequently the capacity may be quite sufficient. Modern flashlights are very efficient and run a very long time at less than full light output, so I just swap batteries every few days with freshly recharged ones, and use medium output levels when I can. Shallow cycles are good for the batteries as well and avoid the cell imbalance and other full discharge problems.

Another comment about capacity is that it is often considerably overstated. At high current the capacity of a primary 123 cell is often half of the stated value (measured at low current). However at high current a LiFePO4 cell may still get very close to full capacity. Thus a 1.5AH primary may yield only 750mAH, and a 500 mAH LiFePO4 may still get 450 mAH. So the capacity difference may not be as much as the low-current values would indicate.

-- Alan

 

[SilverFox]

Hello Chris,

A123 18650 cells are rated at 1100 mAh...

Tom

 

[chanamasala]

Does anyone know where to get A123 18650s and other cells including this one: http://www.a123systems.com/#/products/p1 ;2300 mah. Probably would be a breeze to get a chinese manufacturer to make a 2x26650 torch for us to use them in. A quad R2 setup pulling as much current as desired would be sweet.

 

[mdocod]

This is why it is so important that CPFers stop recommending lights that only fit CR123 size cells to people who may have an interest in going to a rechargeable format. There are no good rechargeable alternatives in CR123 size that can compete with their primary cell cousins. People are constantly pushing people to by lights like the P3D, which is a good light, but it's efficiency really is a moot point when the user desires a rechargeable solution. Next time someone requests a recommendation for a light, ask if they think they will EVER want to go rechargeable, if the answer is YES, then recommend lights that are compatible with 18650 cells, or NIMH AA.

2xAA eneloops (2.4V 2000mAH) have about 30%+ more energy than 2 RCR123s (depending on what RCR123 it is compared to, compared to LiFeP04 cells it's more like 70% more energy).
An 18650 (3.7V 2200mAH) has more than double the energy available than 2xRCR123 (actually as much as triple when compared to LiFeP04 RCR123s).

 

[BVH]

Here ya go

http://www.candlepowerforums.com/vb/showthread.php?t=178188&highlight=emoli

 

[mdocod]

BVH, the cells you linked to are HUGE in comparison to RCR123s, (in fact they are about 5x the size)

 

[BVH]

mdocod, i was responding to this question:

Does anyone know where to get A123 18650s and other cells including this one: http://www.a123systems.com/#/products/p1 ;2300 mah. Probably would be a breeze to get a chinese manufacturer to make a 2x26650 torch for us to use them in. A quad R2 setup pulling as much current as desired would be sweet.

 

[mdocod]

eeek, didn't see that there, sorry.

 

[cave dave]

Hello Chris,

A123 18650 cells are rated at 1100 mAh...

Tom

Why did Silverfox even post this? Has nothing to do with the thread.

P.S. a A123 and a 18650 are two totally different beasts.

A123 is short for single cell 2/3 "A" size, that is 17mm dia & 34.5 mm long. LiIon versions are around 700mAh or less no matter what they claim.

18650 cells are 18mm dia and 65mm long. Available only in rechargeable versions, Capacities are around 2300mAh.

 

[BVH]

"A123" is also a description of the new, safer Lithium cell used in electric vehicle packs and 36 Volt battery tool packs (Like the emoli's). They're made by a company called A123 Systems. This similar designation/company name is sometimes confusing. They're capable of very high discharge rates for Lithiums. Follow my link in my first post.

 

[mdocod]

A123 makes a 26670 size cell based on a special LiFeP04 technology.

 

[Alan B]

Does anyone know where to get A123 18650s and other cells including this one: http://www.a123systems.com/#/products/p1 ;2300 mah. Probably would be a breeze to get a chinese manufacturer to make a 2x26650 torch for us to use them in. A quad R2 setup pulling as much current as desired would be sweet.

You probably mean A123Systems cells in 18650 size, and the easiest place to get them is to buy a Black and Decker VPX battery and remove the two A123Systems 18650 cells from the pack. (I have not done this myself yet, but reportedly that's what is in there). These are the high current LiFePO4 type cells.

However, this thread is about 16340 size LiFePO4 cells, so we won't talk about the 18650's.

-- Alan

 

[SilverFox]

Hello Cave Dave,

The A123 cells come in two sizes, one of which is 18650...

You can check them out here.

Tom

 

[Lighthouse one]

I just got a set of 4 and charger from Battery Junction. Claimed output is 750 mah. They are called 3 volt, and drop to 3.1 to 3.2 when turned on. I got them for my friend at work, and they are doing fine so far. They are just as bright as the Panasonic primaries I use.
http://www.batteryjunction.com/rc375reliba.html

 

[cave dave]

Hello Cave Dave,

The A123 cells come in two sizes, one of which is 18650...

Tom

Wow, I've been around CPF forever and learned something new today. I haven't been paying much attention to the LiPo batteries because I didn't want to add another charger to the mix. I can see how newbies can get confused so easily, what with about 26 different flavors of "lithium" batteries.


PS I think Tenergy is well known for overstating their capacities.

 

[SilverFox]

Hello Cave Dave,

It also get even more confusing when the company name is very similar to a battery size. We are aware of, and use, the CR123 cells, and now along comes a company with the name A123.

By the way, I am doing my testing on the A123 cells by charging them on a normal Li-Ion charger. No problems so far, but I am only up to around 50 cycles on these cells. Think of it as charging a NiMh cell on a NiCd charger, except the A123 cells are more robust than NiMh cells.

Tom

 

[cave dave]

It seems to be an AA Eneloop has a higher energy density than these LiFePO4 cells.

Eneeloop: 1.2v x 2000 mAh = 2400 mWh

16340 LiFePO4: 3.2v x 500 mAh = 1600 mWh

There is a converter efficiency advantage in the higher voltage cell, but if I were looking to buy a "safe" rechargeable light I would go for AA for now.

I think the LiFePO4 does offer a nice solution if you already have a favorite CR123 light that you want to run rechargeable for daily short term use but then switch to primaries for camping weekends and the like. Something like the Fenix single cell models which don't have lower levels on LiIon come to mind.

If you are in the market for a new "safe" rechargeable light maybe a Nitecore DI AA or the Proton Pro would actually perform just as well as a single CR123 light and still have "safe" primary options as well.

PS I think the most "dangerous" aspect of using CR123 & RCR123s right now is the fact it is so easy to mix and match in either the flashlight or the wrong charger. Maybe you know better, but what about your wife and kids? I know from experience that typical consumers mix and match alkalines / heavy duty at will.

 

[SilverFox]

Hello Cave Dave,

Yes, you have to go up to the 18650 sized cell to gain an advantage in watt hours.

As far as safety goes, we have a rule in our household that if the cells die in a light, you simply grab another light. Charging and changing cells is only done by me, or under my supervision.

All of my extra Li-Ion cells are locked up in a fire proof safe. I keep a few loose NiMh cells around and have one charger that I have instructed the family on how it operates (Maha 808M). My family members prefer lights in the 2 AA format, so I also keep a stash of Alkaline cells for emergencies. My wife's favorite "grab to go" light is my ARC LSH-P with the 2 AA battery holder.

The downside to my policy is that I had to get a few extra lights to have on hand... however, we have had no incidents of mixed batteries.

Tom