# Equivalent circuit for a battery.

1. Apr 29, 2015

### Yam

1. The problem statement, all variables and given/known data

An engineer is trying to model a lithium battery with a thevenin equivalent circuit. She first connects a voltmeter across the battery and gets a reading of 3.7V. She then connects 0.5 Ohms resistor across the battery terminals. The reading now drops to 3.2V. Draw the equivalent circuit for the battery and work out the circuit parameters.

2. Relevant equations

I understand how to derive the equivalent circuit but i do not understand what circuit parameters represent

3. The attempt at a solution

VOC=3.7V
R=? I do not know how to derive the internal resistance of the battery also

Now, i dont understand what the circuit parameters mean. What are they asking for?

Last edited: Apr 29, 2015
2. Apr 29, 2015

### Staff: Mentor

In Relevant equations above you stated that you knew how to derive the equivalent circuit.
In this case they are looking for the component values for the Thevenin equivalent circuit (Thevenin voltage and Thevenin resistance).

Show us what you know!

3. Apr 29, 2015

### CWatters

Post the equivalent circuit of the battery and 0.5 Ohm load resistor.

4. Apr 29, 2015

### Yam

Haha! Yes! i solved it after 2 hours haha! thanks guys

5. Apr 29, 2015

### CWatters

What did you get for the internal resistance?