Li-ion series cell voltage

[gaetano.sciacovelli]

Hi,

1) I know that is a very dummy question, but I am not sure about the answer. If I have 10 series cells how can I get a total voltage of 48V? If the single OCV is 3.6V the sum is 36V. Have I to consider to charging voltage?

2) What is the lowest discharge voltage for a single cell ? So what are the corresponding voltages for a full battery charged and a discharged battery?

Thanks.

Regards

 

[SamTexas]

1) LiCo (Lithium Cobalt) and LiMn (Lithium Manganese) have a maximum voltage of 4.20V per cell. So 42.0V is the max for your 10s string. LiFePO4 (Lithium Iron Phosphate) maximum voltage is around 3.70V. So 37.0V.

2) For Laptop LiCo, 2.50V. For RC LiCo (aka LiPo) and LiMn around 3.00V. 2.00V for A123 LiFePO4. Multiply those numbers by the number of cells in series to get the pack voltage.

Add more cells in series to get a higher voltage. For example 13 LiCo in series will give you 54.6V max and 48.1V nominal.

 

[999zip999]

Geatano welcome to Endless-Sphere where you from ? There a lot of good reading and info thru starting with Wiki.

 

[NeilP]

If I have 10 series cells how can I get a total voltage of 48V?

Simple answer is from 10 cells in series you can't.

So as said earlier you need to add more cells.

2) What is the lowest discharge voltage for a single cell ? So what are the corresponding voltages for a full battery charged and a discharged battery?

As Sam says..depends on the chemistry of your cells

 

[amberwolf]

http://www.endless-sphere.com/w/index.php?title=Main_Page#Rechargeable_Batteries

 

[gaetano.sciacovelli]

If I have 10 series cells how can I get a total voltage of 48V?

Simple answer is from 10 cells in series you can't.

So as said earlier you need to add more cells.

2) What is the lowest discharge voltage for a single cell ? So what are the corresponding voltages for a full battery charged and a discharged battery?

As Sam says..depends on the chemistry of your cells

Consider for example a Lithium iron phosphate battery with a nominal cell voltage of 3.3V. In what voltage range these batteries would work?

 

[amberwolf]

Consider for example a Lithium iron phosphate battery with a nominal cell voltage of 3.3V. In what voltage range these batteries would work?

http://www.endless-sphere.com/w/index.php?title=Main_Page#Rechargeable_Batteries

 

[gaetano.sciacovelli]

So when it is fully charged the cell has a voltage of 3.6V. Minimum voltage is 2.8V.

 

[NeilP]

yes. pretty much.

 

[SamTexas]

So when it is fully charged the cell has a voltage of 3.6V. Minimum voltage is 2.8V.

Not really. The highest voltage for LiFePO4 varies. It could go up to 3.7V. The minimum is 2.0V, but there isn't much energy left in the 2.0 to 3.0V range, so people just pick a voltage they are comfortable with.

 

[dnmun]

all of the current BMSs for lifepo4 use 2V-2.1V for the LVC and 3.9V for HVC. fully charged for lifepo4 is 3.65V. this is widely available info. no need to ask for random answers.

 

[SamTexas]

If I want accurate data about my LiFePO4 cell or any cell, I would consult the manufacturer datasheet. The last thing I want to believe is any data published/used/recommended by those BMSs. 3.9V? Did they just pull that number out of the air?

 

[dogman dan]

Ding, here we go! But after the discussion settles, you find that the generally accepted fully charged voltage for lifepo4 is about 3.6-3.65v per cell. The convention for lifepo4 is 12s is "36v" and 16s is "48v". You will also see the number 3.5v used, because that last bit of voltage between 3.5v and 3.65 usually packs very few watthours. Older cells will self discharge to 3.5v or lower immediately after removing from the charger at 3.65v.

But they do get charged higher in some battery /charger/ bms systems, so balancing of cells can be accomplished by some bms's. My pingbattery lifepo4 finished charging and balancing at 3.75v per cell. I suppose that the 3.9 number is a stop before it gets too damaged setting, not the recomended charge to voltage.

So charge lifepo4 to 3.6v at least, to get them full. But expect them to drop to no more than 3.5v very quickly, then spend most of the discharge at about 3.3v.

That's for lifepo4. For lico or "lipo" the charge to number is usually 4.2v per cell. Niether chemisty gets 48v from 10s.