Lithium-Ion Battery Model

Dear All,

I have to design a rechargeable battery charger. This is the first time I am designing a battery charger circuit. Therefore, I need to clarify few thing from the experienced designers out there. Please help me in this regard.

I have already studied the charging profiles and schemes for the Li-Ion and the Ni-MH rechargeable batteries. I am listing my confusions and question as follows.

Q.1. What will be the battery model that should be considered for designing a battery charger. Is it mandatory to consider the discharging profile of the battery as well for charger design? If I consider an equivalent capacitance (C_bat) corresponding to the capacity of the battery, will it be enough for emulating the battery in my circuit simulation?

Q.2. Lets assume the battery internal impedance given in datasheet of a given battery is R_b. Now, my question should R_b be considered in series with the C_bat?

Q.3. Will this minimal capacitive model representing only the charging port of the battery be used for both transient and ac analyses?

Please help me to select a correct (approximately) electrical circuit model for a rechargeable battery.

Thanks
Sam.

Hi,

Q1: I don´t hink so. Imagine a discharged capacitor. Charged with constant current: The voltage will follow a straight line from zero to target voltage.
A battery´s voltage behaves very different

Q2: battery impedance is a series impedance ... to the ideal battery.


Klaus