Li-ion Vs LiFePo4

[jly_albk]

Hi mates,

I was investigating about both kinds of battery cells, and as far as I know, for equal sizes (26650, for example) Li-ion offers higher capacity 4200 vs 2500mah and higher energy density.On the other hand, LiFePo4 are safer and works better at high temperatures.

The main doubt is about discharge rate. Could anybody make it clear?

I would appreciate if someone is able to tell more differences between these batteries.

BR

 

[Drunkskunk]

Well, to start, LiFePO4 is a Li-ion battery. There are many types.

The highest power density is Lithium Cobalt (oxide) (LiCo or LiCoO2). In between are Lithium Manganese (LiMn), Lithium Manganese Cobalt (LiMnCo), Lithium Nickle Manganese (LiNMn), and Lithium Nickle Manganese Cobalt (LiNMnCo).

The discharge rates are variable depending on the quality of the construction. LiCo in a polymer format has the lowest internal resistance, so the highest potential discharge rate, however, there are plenty of LiCo cells available that aren't safe for more than 1 to 2 C discharge rates, while a123 brand LiFePO4 cells were capable of something like ~50c discharge. It really depends on the individual cell, and not the specific chemistry.

 

[friendly1uk]

I think LiFePO4 is safer and lasts longer, but for everything else lipo wins.

Slight chance I'm wrong though..

 

[jly_albk]

thanks for replaying.

I called them li-ion because seller don´t specify if they are LiCo, LiMn and so on.

The point is that I though to change on my electric car the LV system. By now, a A123 LiFePo4 26650 4s4p is mounted (12,8Vnom@5Ah - 70A aprox discharge current) but we need higher capacity and expect keep weight, and discharge rate.

I´ve found these http://www.aliexpress.com/item/Free-Shipping-NEW-2pcs-SOSHINE-26650-4200mAh-Protected-3-2V-Rechargeable-LiFePO4-Battery/1677432994.html
but don´t really trust in what sellers say due to they name them LiFePo4 but they say the nominal voltage is 3,2V..

should I trust in these "Li-ion" cells"?

 

[Gregb]

Sounds like that is what your battery is....4x 3.2V. 4s means 4 in series which gives you 12.??........ the actual discharge current will be determined by your load ie controller and motor and the structure of the cells..the 4P refers to the number in parralel to give you the AH rating or expected capacity. some sellers/manufacturers put the 3.6 or 3.7 V on as that is the max you can charge them to. Bit of a con and the capacity is < 5AH but they are pretty similar to your existing setup from those figures. I know NOTHING about the quality

 

[jly_albk]

Thanks for your opinion.

The point is that most sellers says "li-ion 3,7@4,2ah" but are not specific with kind of li-ion.
On the linke above there were some mistakes, onces you are in, you see that Vmax is 4,2, so he doesn't mean LiFePo4.

Could LiPo be more conenient to my application?

I want to change the config aiming to get 13-14V@8-10Ah, and I don't mind decreasing a little bit the discharge rate but not too much and not increasing weight either.

Should I move to LiPo?

 

[Drunkskunk]

Well, that depends. Lipo (Lithium Polymer) is isn't a chemestry either. Its a name for a cell construction. Lithium Polymer cells use a polymer to hold the electrolyte instead of a liquid found in most round cells. Lipo cells are usualy the flat pouch cells, although the format can be built into the same round cans that traditional cells use.

The voltages you specified would be good for either LiCo, LiMn, or LiMnCo

It might help to know what it is you're building, or what specifics parameters you need.