LiPo Battery model on LTspice (Help)

Thread Starter

santiaznarez

Joined Jul 18, 2020
5
Hi, I'm not sure if this is the correct forum to post this! But I haven't found a more suitable one for this.
I need to simulate a LiPo battery of a single 3.7v cell on LTspice using only passive components. I know my circuit would be based on capacitors and resistors but I really can't find a way to develop this type of battery.
 

Papabravo

Joined Feb 24, 2006
14,688
Hi, I'm not sure if this is the correct forum to post this! But I haven't found a more suitable one for this.
I need to simulate a LiPo battery of a single 3.7v cell on LTspice using only passive components. I know my circuit would be based on capacitors and resistors but I really can't find a way to develop this type of battery.
I do not think such a simulation is possible. (Apparently it is -- see 2nd link). Is there some reason you cannot use a behavioral voltage source. It would certainly allow you to model the discharge behavior, given a discharge profile which could also be described by a behavioral source.

You might find these articles helpful:
https://www.pspice.com/resources/ap...-simulate-discharge-behavior-common-batteries
http://ltwiki.org/?title=Modelling_a_Ni-MH_battery_with_hints_on_Li-Ion_battery_modeling
http://www.eng.auburn.edu/~agrawvd/TALKS/VDAT10/160_ST.pdf

I was not aware of the non-linear capacitor. Thanks for leading me to discover it.
 
Last edited:

Irving

Joined Jan 30, 2016
1,069
I model a lipo battery with a capacitor to maintain state of charge (SoC) driven by a current source for charge and a current sink for discharge (charge ~10% higher than discharge, you put more in than you get out!) and two perfect switches controlled by the external current direction. The linear voltage 0 - 100 on the SoC capacitor is used to drive a voltage source via a look-up table that maps SoC to open circuit voltage (OCV) . I use a fixed internal impedance (5 - 50mohm, depending on model) between the OCV and the external terminal. The SoC/OCV table and impedance are based on averages of measurements taken from many lipo cells I've owned. Its not a perfect simulation but it works well enough to design and simulate chargers, balances, etc. I did model internal impedance v SoC v output current but it's tricky to do and for most purposes on small 1S & 2S to ~10Ah+ the fixed value works just as well. I have a more complex simulation that models my 5kW LiFePO4 pack quite well too.
 

Thread Starter

santiaznarez

Joined Jul 18, 2020
5
I model a lipo battery with a capacitor to maintain state of charge (SoC) driven by a current source for charge and a current sink for discharge (charge ~10% higher than discharge, you put more in than you get out!) and two perfect switches controlled by the external current direction. The linear voltage 0 - 100 on the SoC capacitor is used to drive a voltage source via a look-up table that maps SoC to open circuit voltage (OCV) . I use a fixed internal impedance (5 - 50mohm, depending on model) between the OCV and the external terminal. The SoC/OCV table and impedance are based on averages of measurements taken from many lipo cells I've owned. Its not a perfect simulation but it works well enough to design and simulate chargers, balances, etc. I did model internal impedance v SoC v output current but it's tricky to do and for most purposes on small 1S & 2S to ~10Ah+ the fixed value works just as well. I have a more complex simulation that models my 5kW LiFePO4 pack quite well too.
Great! I would try that, my professor told us it may be useful to model it like a flyback architecture, what do you think?
 

Thread Starter

santiaznarez

Joined Jul 18, 2020
5
I model a lipo battery with a capacitor to maintain state of charge (SoC) driven by a current source for charge and a current sink for discharge (charge ~10% higher than discharge, you put more in than you get out!) and two perfect switches controlled by the external current direction. The linear voltage 0 - 100 on the SoC capacitor is used to drive a voltage source via a look-up table that maps SoC to open circuit voltage (OCV) . I use a fixed internal impedance (5 - 50mohm, depending on model) between the OCV and the external terminal. The SoC/OCV table and impedance are based on averages of measurements taken from many lipo cells I've owned. Its not a perfect simulation but it works well enough to design and simulate chargers, balances, etc. I did model internal impedance v SoC v output current but it's tricky to do and for most purposes on small 1S & 2S to ~10Ah+ the fixed value works just as well. I have a more complex simulation that models my 5kW LiFePO4 pack quite well too.
By any chance do you still have that circuit on spice?
 
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