Safe chemistry LiMN 3.7V rechargeable batteries?

[StorminMatt]

not true .. state of charge can be determined easily by a simple voltage reading. for single cell that takes a precision volt meter which the average consumer doesn't have. but for four cell in series like for 12v Motorcycle LiFePO4 batteries. it's easy to determine state of charge with a VOM.

here's a state of charge chart for 12v LiFePO4

As far as determining the state of charge based on voltage, you can see here that there's only a .2V difference between 80% and 20% state of charge with 6V (or around half a volt for 12V). This is FAR, FAR, FAR less than you would see with, say, LiMn, LiCo, or lead acid. And it is well within the range of error you would get using even a very accurate DVM due to such factors as a little oxidation on the terminals or leads. With LiFePO4, a better way to measure capacity would be to know how much current you have been drawing for how long.

Anyway, speaking of the use of LiFePO4, it's also finding use for off grid solar power. Compared to lead acid, it not only has a more stable voltage. It also lasts longer and is less maintenance intensive. And it takes up FAR less space (and weighs less) for a given capacity. There is also no worry about losing a battery that never gets fully charged (say, due to extended cloudy/rainy weather in the short days of winter) from sulfation. LiFePO4 is more expensive than flooded lead acid. But it is actually quite cost competitive with AGM batteries.

 

[cy]

As far as determining the state of charge based on voltage, you can see here that there's only a .2V difference between 80% and 20% state of charge with 6V (or around half a volt for 12V). This is FAR, FAR, FAR less than you would see with, say, LiMn, LiCo, or lead acid. And it is well within the range of error you would get using even a very accurate DVM due to such factors as a little oxidation on the terminals or leads. With LiFePO4, a better way to measure capacity would be to know how much current you have been drawing for how long.

Anyway, speaking of the use of LiFePO4, it's also finding use for off grid solar power. Compared to lead acid, it not only has a more stable voltage. It also lasts longer and is less maintenance intensive. And it takes up FAR less space (and weighs less) for a given capacity. There is also no worry about losing a battery that never gets fully charged (say, due to extended cloudy/rainy weather in the short days of winter) from sulfation. LiFePO4 is more expensive than flooded lead acid. But it is actually quite cost competitive with AGM batteries.

yup discharge curve is almost flat once voltage makes initial drop .. so yes a very accurate volt meter would be necessary to determine state of charge. note in 12v or 4x series configuration voltage differences is multiplied. so a voltmeter with normal accuracy range will work fine.

for all practical purposes 12v LiFePO4 operates at 13.3v range within 1/2v .. cost effectiveness of LiFePO4 is a hard sell vs AGM for most stationary applications. but for motorcycles it's one of the most cost effective way to drop lbs.

someone that's riding a $10k+ motorcycle think nothing of spending $250+ for a 12v LiFePO4 battery that will shave say 6-10lb+ from their bike. it's the fastest selling 12v LiFePO4 batteries sector that I'm aware of.

 

[abies]

Just to bring up a common error when referring to IMR cells, IMR cells are LiMn2O4 cells and are often referred to as "LiMn" (Li=lithium, Mn=manganese), not "LiMN". "LiMN" is usually used when referring to certain Li-Ion cells which contain both manganese (Mn) and nickel (Ni) in the positive electrode, which IMR cells do not.

LiMN, or lithium manganese nickel cells, are closely related to (but not quite the same as) the Redilast and AW 2900mAh cells (which are actually Li-NiCoAl), for example. Most of this general family of cells, which tend to also operate at a higher voltage, also contain cobalt in the positive electrode, which IMR cells do not. This fact is mostly why IMR cells are considered to be a "safer" chemistry.

On batteryspace, it seems there is a confusion between LiMnNi and NiMn2​O4​.
I suppose IMR are of better quality than these?