LiFePo4 vs LiCo 18650 cells??

[jawnn]

[FONT=Trebuchet MS, sans-serif]Ifit is true that LifePo4 cells are much more stable than LiCoAl ormanganese? I want to buy about 250 cells to use in an Ebike pack. Butis it true that I they can hold 3000mAh in each 18650 cellwithout over charging them? Canthey be charged to 4 volts each? What voltage can theyhold without being in the danger zone? That seems like one of those false Chinese claims.[/FONT]


[FONT=Trebuchet MS, sans-serif]Iknow that if they heat up the electrolyte will deposit resistantmaterials on the cathode like any of the cells do. So I need tofigure out how many I need to keep them form heating up. Mycontroller is a 40 amp but a little higher is possible. [/FONT]

 

[eh4]

My understanding is that the energy density of LiFePO4 cells is about comparable to NiMH, and not nearly the capacity of the more dangerous lithium chemistries.

 

[HKJ]

I will suggest you study LiIon performance on my website, use this table: https://lygte-info.dk/info/batteryIndex.html

The best LiFePO4 cells I have seen: https://lygte-info.dk/review/batteries2012/Enerpower 18650 3.2V 1800mAh (Blue) UK.html
With ordinary LiIon it is: https://lygte-info.dk/review/batteries2012/Samsung INR18650-35E 3500mAh (Pink) UK.html

 

[jawnn]

I was looking at a listing of the cells and discovered that aI will have to cram a lot more cells in my small space [h=1]8 x 3.2 Volt 26650 LiFePO4 Batteries (3300 mAh) how do these compare to samsung 29E cells?[/h]

 

[snakyjake]

Advantages: stable + safe + recharge cycle + don't cutoff.
Disadvantages: runtime. But for my normal use, runtime isn't a priority. I can topoff or swap batteries.

 

[Rexlion]

I'm also on some RV forums, and the RVers who are adopting newer battery tech are all buying LiFePO4 batts. RVs get bumped around a lot on rough roads, and the batteries get abused by being discharged more deeply than they ought. LiFePO4 is considered by those people to be the safe and effective way to go. They figure if the furnace drains the batt to 20% overnight, a LiFePO4 will bounce back better than any other type.

As for what's best on a bike, I don't know. Just passing on what I've heard from others.

 

[WalkIntoTheLight]

I'm also on some RV forums, and the RVers who are adopting newer battery tech are all buying LiFePO4 batts. RVs get bumped around a lot on rough roads, and the batteries get abused by being discharged more deeply than they ought. LiFePO4 is considered by those people to be the safe and effective way to go. They figure if the furnace drains the batt to 20% overnight, a LiFePO4 will bounce back better than any other type.

As for what's best on a bike, I don't know. Just passing on what I've heard from others.

As well, 4 LiFePO4 cells in series are a good match for a traditional 12v lead-acid battery. A lot of RV stuff is designed for 12v.

 

[IonicBond]

The "stability" of LiFeP04 you speak of is basically that FeP04 component is iron-phosphate.

Iron, even if abused, does not allow oxygen molecules to escape. One of the major components of fire.

Thus you can abuse them, and vent (cook off the electrolyte), but this is far different than other li-ion chemistries without iron, that "vent with flame".

Thus, motorcycle starter batteries, like Shorai, Antigravity, and other manufacturers all use LiFeP04, since they are often sitting a few inches away from your butt. You don't want an accident to produce flame there.

The disadvantage is that they are not as power-dense as other li-ion chemistries (typically those that are 3.7v nominal), and make for a much larger package on your vehicle.

Many early exciting li-ion failures and media frenzy when lifepo4 batteries were used were not actually due to the batteries being bad, but by the wiring / charger infrastructure burning up - and destroying the cells in the process. But the media didn't understand lifepo4, and needed a scapegoat.