AA Lithium Iron Phosphate batteries

Rickharris

Senior Member
I see on the interweb that these AA Lithium Iron Phosphate (LiFePO4), are becoming available.

With a rated voltage on these is 3.2 V. they look very suitable for driving Picaxe ccts


Does anyone have any experience with these batteries?
 

Dippy

Moderator
Aren't some of the Li-Ion types of that same construction?

Anyway, when I did a Google the first 2 hits were Alibaba and Ebay... my favourites... so I'll let you try them first Rick ;)
 

Andrew Cowan

Senior Member
I've used them (or at least lithium ones with a voltage of 3.7v). I've mainly used the larger 18650 size cells, although I have also used standard AA size.

I'd recommend getting batteries with a built in PCB to stop over discharging - it can damage the batteries (or much worse!) if you take them below 2.75v per cell. Having the cutoff built in makes them much easier to use. Note - these PCBs make the cell slightly longer than an AA cell - but since the voltage is higher, you won't be using it in an AA device anyway.

They are excellent at supplying high currents (a few amps), and once cell will happily run a PICAXE. They need a specific charger, but once you have one, you can't go wrong!

A
 
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BeanieBots

Moderator
Not as fragile as LiPo but how will you charge them.
They have different charge requirements to the more common LiPo so you cannot use the more readily available LiPo chargers.
 

cactusface

Senior Member
Battery power

Hi All,
If you own a digital camera/camcorder and I feel sure many of you will, these are usually powered by Lith-ion batteries either at 3.6V or 7.2V, (a few still take 4xAA). Manufacturers like Energizer and Hahnel produce generic batteries and chargers for these, but they also produce adaptor plates to take just about any size and style of cell.

These adaptor plates also make it very easy to use these batteries to power your buggy, robot, data logger, etc (Get a spare plate, and fix it in to your project) and you will already have the charger for it too.

I understand there are a few different Lithium battery systems at work at the moment....
Hope this might helps! and give someone an idea!!
Regards
Mel.
 

Dave E

Senior Member
I believe what rickharris is looking at are Westinghouse AA batteries. I found some in the solar lighting section at Walmart. They are 600mAh, 3.2 volt LiFeSO4 AA batteries. Pack of 4 cost $10. These are 14mm in diameter like AA batteries but there were also larger diameter batteries but with the same electrical rating.
The first thing I thought of when I saw them was single battery projects for Picaxe chips. However, I am not able to find much info about charging these on the web. So far I have not been able to locate any info on the web from Westinghouse about them.??

Some info I found suggests a max charge voltage of 3.6 volts. However, I have not been able to confirm that.
I may take one of the lights apart to take a look at how the 2 small solar panels are used to charge them. The lights came in a 4 pack but I only need 3.;)

Dave E

The particular lights I bought use a single rechargeable NiCad (1.2V).
 
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Dave E

Senior Member
Thanks, Dippy.

The specifications are the same as the source I saw. The 5 minute charge time is new though.
Both charts look the same to me as far as I can tell. Both look like the charge cycle chart. Which is ok since that is what I was looking for.

Dave E
 

manuka

Senior Member
FWIW -and quite some years later- my recent LiFePO4/LFP experiences gained during an extensive EU family outing were very positive. Our assorted LFP AA/AAA battery powered flashlights, shavers, cameras, instruments, radio gear etc performed brilliantly.As significant travel was via EU's infamous no frills airlines,weight & bulk were trimmed by ditching the usual NiMH cells,cussed mains adapters & chargers to use LFP 14500/10440 types instead. Most recharging was via a 2 finger sized 'Soshine" USB smart charger,which was both a compact sweetie and rapid in action. USB sockets globally now abound on even plane seat backs & hotel PCs/TVs etc, & no qualms arose from picky airline security over spare charged cells.

N.B. The rapid charging feature of LFP can be particularly valuable when on the run. Being able to top up in a hurry from a small charger is a life saver - 500mA at 3.6V takes only ~90 mins to store into a ~700mAh 3.2V LFP, whereas the same current into a ~2000mAh 1.2V NiMH would take >4 hours to stash away much same usable energy. Your appliance would probably need multiple NiMH cells as well.

I'd sourced all gear cheaply pre trip via FastTech in Hong Kong, but - probably as a result of a heads up LFP article in the June 2013 "Silicon Chip"- Australian outlet Jaycar (at least) is now also considering stocking them. However it'd be hard to match FastTech's dirt cheap prices & globally free posting!

As lithium batteries look on a real roll,any other user feedback (both +/-) may hence be worth posting to build up the AA/14500 (14mm x 50mm) knowledge base.

Footnote:Although less energetic than similar Li-Cobalt(Li-ion) types, the steady 3.2V output of LFP (+ a simple series place holding dummy cell) nicely matches the voltage of 2 x fresh alkaline AAs of course. Li-cobalt (Li-ion) deliver 3.7V per cell, which may overdrive many consumer devices, even if dummy cells are used! I'm not LFP biased, but they certainly look inherently much safer and more abuse tolerant than Li-ion/Li-poly,with far greater recharge ability (~1000s versus mere 100s for Li-ion).

Stan.
 

SteveT

Senior Member
Just for info, most of the modern 4 button Chinese ballance chargers can charge LiFePO4, Lithium Polymer, Lithium Ion, Nicad, NimH and Lead Acid batteries. Less than £20 if you have your own power supply of 11 to 18v @ 500mA (min) to about 6A. Or round about £30 for one with a built in power supply. The one I have (B6AC) is 80W with a built in power supply. Recommend it to anyone.
 

srnet

Senior Member
Li-cobalt (Li-ion) deliver 3.7V per cell, which may overdrive many consumer devices, even if dummy cells are used!
3.6V for Lithium Ion and 3.7V for Lithium Polymer, are the nominal voltage only.

At full charge they can be 4.2V and 4.1V respectively.
 

manuka

Senior Member
Li-ion/Li-Poly indeed begin delivery at 3.6-3.7V but this steadily drops to under 3V during use. LiFePO4 are charged to 3.6V but their delivered supply remains at a remarkably steady 3.2-3.3V until ~ 90% exhausted.

EXTRA: Dreamliner news again => http://www.bbc.co.uk/news/uk-23302722 , although perhaps this time just someone smoking in the toilets...
 

Puuhaaja

Senior Member
I'd recommend getting batteries with a built in PCB to stop over discharging - it can damage the batteries (or much worse!) if you take them below 2.75v per cell. Having the cutoff built in makes them much easier to use. Note - these PCBs make the cell slightly longer than an AA cell - but since the voltage is higher, you won't be using it in an AA device anyway.

A
It's often mentioned that voltage below 2.75V can destroy lion battery. Last october I dropped my diving torch when I was diving. 6 months later I found my torch. It had been under frozen lake several months but I got it working. Batteries voltage was 1,2V because pcb had blocked batteries. I took pcb off and measured voltage which was then 2.05V. Charger didn't start to charge battery due to low voltage of battery. I solved proglem so that I charged batteries little time using 5v until batteries voltage was about 2,9V. After that I was able charge them fully using prober charger.

I had made my own torch burning time tester using Picaxe: https://dl.dropboxusercontent.com/u/16735593/2013-02-22 06.54.40.jpg
After charging I tested torch burning time and it was nearly same as it was when it was new. So... my point is that in some cases lion betteries can be reactivated even if they had been under 2.75V several months.
Anyways...I will never buy lion batteries without pcb.
 

premelec

Senior Member
I gather there are available "protected" cells with the electronics built into the cylindrical device - probably a MOSFET in series with the output. I have had various results with getting 'old' computer Li batteries to hold charge... I wish they'd put more data on the cells as to their chemistry etc...
 

Paix

Senior Member
@Manuka, you probably know already, but the other day it was said that the fire was caused by batteries in some form of emergency beacon. That would explain the location on the kite, but other than that I don't know any more.
 
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