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LTSpice model of LiFePo4
von Der D. (derdaniel)

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Hi,

Attached is an LTSpice file and pictures where I'm trying to simulate an 
A123 LiFePo4 Battery (discharge only for now).

On the very left, there is the current controlled current source F1 
mirroring the current through E1. By doing this it's charging C1 and 
therefore showing the discharge status (0V full, 2.3V empty) of the 
simulated Battery.
I1 is a constat current soure supplying 1A and generating the charge 
dependent volltage of the Battery over R2 with the long equation on 
the bottom.
The voltage controlled voltage source E1 finally generates the output 
voltage of the battery.
R4 is only for simulating the empty battery by making it tristate.
I2 simulates the load.

The Equation is based on several discharge courves of LiFePo4s between 
1C and 20C discharge rate. Not mentioned (for now) is the capacity loss 
at high discharge rates. (Please tell me if i shall explain it more 
detailled)

My final goal is a chargeable and dischargeable simulation of LiFePo4 
Packs for small number of cycles (no cycle aging) and self set capacity 
differences to engineer a balancer.


What do you think about my simulation? Whats improvable or which other 
way could it be done.


King regards
--Daniel

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Re: LTSpice model of LiFePo4
von Biju S. (biju_s)

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Hi,

Your simulation looks interesting and I am trying to do similar 
simulation for lithium nickel cobalt oxide battery. Can you please post 
the simulation file for LTspice(the one with asc extension?

Thanks
Biju

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Re: LTSpice model of LiFePo4
von Helmut S. (helmuts)

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Hello Daniel,

1.
Such a small resistance value of 1n is a bad idea regarding convergence 
of a simulation. Better use 0.1m or 1m.

2. Never use automatically assign net names like N001 in any equation. 
LTspice may give it another name when you change the circuit in the 
future.
Always assign a name or number to the nets used in equations.

3. The attached .raw-file is useless. You should attach the 
schematic(.asc).

Helmut

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Re: LTSpice model of LiFePo4
von Thom Stevens (Guest)

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I have recently brought a simulation of a large capacity LiFePO4 to 
maturity.  There seem to be a few factors that are being neglected - 
most notably is the effect of instantaneous temperature on the the 
internal impedance.  The change in impedence will have a significant on 
the effective energy extracted or stored.

I'd be happy to examine your model in detail but you must attach the 
circuit file if you'd like me to look at it.

Kind Regards,
-Thom

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