Took another look at LiFePO4 batteries.
Much safer than other lithiums, looks harder or even almost impossible to have thermal runaway even with significant overcharging.
Also seems to be available now in the standard 18650 size. A bit lower in voltage, not as much energy density, but over 1000 cycles and way safer.
Read up on tjhem, and download and view the presentation in the link in the text.
http://www.batteryspace.com/lifepo4rechargeablesinglecells1c-30crate.aspx
Greg
I’ve only converted two Bachman locos, but with those weights in them, I thought “heck, take out the weights and just use heavy batteries”, so NiMH for me. But LiFePO is clearly great.
There’s no link in the text. In fact,there is almost no text.
Interesting. But what happened to the 14.4 V packs?
Steve, you might have to back up the breadcrumbs menu at the top, maybe because they don’t want you to go right to the page…
Try this: http://www.batteryspace.com/prod-specs/HLCF18650PLi-ion.ppt
should take you right to the powerpoint presentation
Greg
The link is good, but Steve might have a problem with the Chingish in that presentation. I really learned nothing from it, but I did watch it while the coffee was brewing.
Steve - read this one if you haven’t already. Written in real English and actually makes some sense.
Ross Mansell said:
Read all about it!
sorry, thought the powerpoint was self-explanatory… charts were mostly voltage or current vs. time.
Greg
p.s., I don’t think this is any easier to understand especially if current vs. time does not make sense:
"
One important advantage over other lithium-ion chemistries is thermal and chemical stability, which improves battery safety.[7] LiFePO
4 is an intrinsically safer cathode material than LiCoO2 and manganese spinel. The Fe-P-O bond is stronger than the Co-O bond, so that when abused, (short-circuited, overheated, etc.) the oxygen atoms are much harder to remove. This stabilization of the redox energies also helps fast ion migration.[citation needed]
As lithium migrates out of the cathode in a LiCoO2 cell, the CoO2 undergoes non-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states of LiFePO
4 are structurally similar which means that LiFePO
4 cells are more structurally stable than LiCoO2 cells.[citation needed]
No lithium remains in the cathode of a fully charged LiFePO
4 cell—in a LiCoO2 cell, approximately 50% remains in the cathode. LiFePO
4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.[5]"
oh well… for those of you interested, you can buy them now. Greg
Thanks, Greg, Ross and Jon.
Let’s see if I understand… Safer, by pfm. Less energy density, but after a year, they seem to have the same density as the LiIon, because of a slower decay rate, sitting on the shelf. Able to leap tall buildings, faster than a bullet, more powerful than a speeding locomotive… (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)
Have I missed anything?
Greg Elmassian said:
sorry, thought the powerpoint was self-explanatory… charts were mostly voltage or current vs. time.
Greg
p.s., I don’t think this is any easier to understand especially if current vs. time does not make sense:
"
Safety
One important advantage over other lithium-ion chemistries is thermal and chemical stability, which improves battery safety.[7] LiFePO
4 is an intrinsically safer cathode material than LiCoO2 and manganese spinel. The Fe-P-O bond is stronger than the Co-O bond, so that when abused, (short-circuited, overheated, etc.) the oxygen atoms are much harder to remove. This stabilization of the redox energies also helps fast ion migration.[citation needed]As lithium migrates out of the cathode in a LiCoO2 cell, the CoO2 undergoes non-linear expansion that affects the structural integrity of the cell. The fully lithiated and unlithiated states of LiFePO
4 are structurally similar which means that LiFePO
4 cells are more structurally stable than LiCoO2 cells.[citation needed]No lithium remains in the cathode of a fully charged LiFePO
4 cell—in a LiCoO2 cell, approximately 50% remains in the cathode. LiFePO
4 is highly resilient during oxygen loss, which typically results in an exothermic reaction in other lithium cells.[5]"oh well… for those of you interested, you can buy them now. Greg
Hmmmm… Wanna discuss the Kreb’s Cycle? (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-surprised.gif)Its as easy to understand. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)
Yes, you have indeed missed something. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)
Basically much safer because you can overcharge them and they basically won’t catch in fire, in the powerpoint the test was done with a 10C charge rate, and overcharged.
That will normally make any lithium catch on fire.
This is a big deal, and they are finally available as individual cells and from all appearances are doing fine. they are also very common in the electric cars, and we know the safety (really liability) concerns of the car manufacturers.
It’s cool if you don’t care, but if you were concerned and wanted to use lithium cells, this is an opportunity that is available now. So this is for the people who have those concerns.
Greg
That’s why I said its safer… (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-innocent.gif)I don’t have to understand it to the point of being able to replicate the science, just enough to keep from burning my fingers. I’ll be looking to source LFP batteries the next time I purchase a battery(s).
BTW, Krebs Cycle should be right in your wheelhouse Greg. Its got cations, anions, current flow charts, energy expenditure diagrams, waste disposal, all that sciencey stuff that you like. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-innocent.gif)
Greg,
I’ve had limited experience with LiFePO4 batteries as compared to others, several years ago I was given some to evaluate and experienced some issues with sustainability. Later on the problems seem to be resolved and for the most part the twenty or so LiFePO4 batteries I have work as advertised.
Anyway I believe LiFePO4 batteries are here to stay and offer many desirable attributes as well.
Michael
What I have not researched is chargers for them, they must exist, but I think most chargers make assumptions on the terminal voltage at the end of charging (I know that sentence is probably redundant), so those would probably not terminate charge successfully.
Did you find suitable chargers and if so, would you be so kind to share your info?
Greg
Greg Elmassian said:
What I have not researched is chargers for them, they must exist, but I think most chargers make assumptions on the terminal voltage at the end of charging (I know that sentence is probably redundant), so those would probably not terminate charge successfully.
Did you find suitable chargers and if so, would you be so kind to share your info?
Greg
Greg, my Tenergy TB6AC charger has settings for many different battery chemistries, one of which is LiFe, which I suppose is the LFP battery under discussion.
Thanks Steve…
Went to the site and they make an entire line of LiFePO4 chargers, all seem to be “set” to one voltage as you can see:
http://www.tenergy.com/Site/LiFePO4-Chargers
Seems that the terminal voltage is “locked in” to the charger.
Interesting, would like one with switchable number of cells.
Will research further.
Greg
I think the TB6 Series will do different numbers of cells.
Greg,
I have a several year old Hyperion EOS0615i DUO3 and a Multiplex LN-6015. Both chargers are great units IMO.
Michael
Steve, I read the manual for your charger.
It does indeed have the proper terminal voltage, it cuts off on the LiFe setting at 3.6 volts, and many manufacturers recommend a cutoff of 3.65, so that works. The manual does not LiFEPO4, but only LiFe, but the web site says the charger is good for LiFePO4.
And I can see how you can set it wrong. I think a lot of the battery failures reported are by using a universal charger and setting it wrong.
(Of course I would only buy a universal charger myself (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-smile.gif))
Greg
