# Lithium Ion Battery Cell voltage vs SOC vs Amp hours

#### MikeJacobs

Joined Dec 7, 2019
226
I am trying to figure out how to explicitly correlate battery Amp hours with State of charge and voltage

So as we generally accept, an Lithium Ion cell

Has a min low voltage of 3.2V and a max of about 4.2 volts

ok great no issues here. We also would say that at 4.2 volts its at 100% SOC and at 3.2V its at 0% SOC???? Is that true?

Also, i have a 1 amp hour battery and i drain 1 amp out of it for one hour long
i will be at 0% SOC but is that 3.2V or is that 0V??

Im trying to understand how amp hours relates to SOC is the big question here.
If i drain all the amp hours out of an Lithium ion cell, is it at 3.2V or is at 0V??

Thanks

#### sghioto

Joined Dec 31, 2017
5,368
I would say appx 3.2 volts but does depend on the manufacturer's specs.

#### MikeJacobs

Joined Dec 7, 2019
226
I would say appx 3.2 volts but does depend on the manufacturer's specs.
I am not sure which part of the question you are answer.

#### nsaspook

Joined Aug 27, 2009
12,747
If it goes into BMS under-volt protection it might be 0V until the condition is cleared by a recharge cycle. Normally about 3.2V is 0% SOC

Last edited:

#### sghioto

Joined Dec 31, 2017
5,368
I am not sure which part of the question you are answer.
3.2 volts at 0% SOC

#### MikeJacobs

Joined Dec 7, 2019
226
3.2 volts at 0% SOC
Thanks

But what im trying to understand is, if you remove 1 amp for one hour from a 1Ah battery what is the cell voltage?
Is it 3.2V or is it 0V?

Im trying to understand the correlation between amp hours , cell voltage and SOC

#### sghioto

Joined Dec 31, 2017
5,368
But what im trying to understand is, if you remove 1 amp for one hour from a 1Ah battery what is the cell voltage?
Is it 3.2V or is it 0V?
Appx 3.2 volts. From what I've read at 3.3 volts a lithium ion battery has used up appx 95% of it's charge.

#### MikeA

Joined Jan 20, 2013
364
Has a min low voltage of 3.2V and a max of about 4.2 volts
If max is 4.2V then the battery must be 3.6V nominal, which is considered 50% SOC, thus 3.0V would be 0% SOC, no?

#### sghioto

Joined Dec 31, 2017
5,368
If max is 4.2V then the battery must be 3.6V nominal, which is considered 50% SOC, thus 3.0V would be 0% SOC, no?
No.