Introduction to battery-management systems- COURSERA WEEK 04 QUIZ -1.4.4 ANSWERS

 

Practice quiz for lesson 1.4.4

Total points 3

1.

Question 1

Suppose that a negative-electrode material has $\theta_{0\%}^{\rm neg}=0.01$ and $\theta_{100\%}^{\rm neg}=0.81$. If $\theta_k^{\rm neg}=0.61$, what is the present cell state-of-charge (in percent)? Round to the nearest percent.

1 / 1 point

75

Correct

Yes. State of charge equals $(\theta_k^{\rm neg} - \theta_{0\%}^{\rm neg})/(\theta_{100\%}^{\rm neg} - \theta_{0\%}^{\rm neg})$.

2.

Question 2

Suppose that a lithium-ion cell having total charge capacity $Q=10$Ah is discharged at a rate of 1A for 30min. What is the net change in the cell's state of charge (in percent)? Round to the nearest percent. (Hint: I am looking for a signed answer -- the answer is positive if the state of charge increases and it is negative if the state of charge decreases.)

1 / 1 point

-5

Correct

Yes. The total charge removed is 0.5Ah, which is 1/20 of the cell's capacity, or a decrease of 5%.

3.

Question 3

Consider the battery pack drawn below, where one cell has state-of-charge of 0% and the other cell has state-of-charge of 100%.

Which of the following statements is most accurate regarding the battery pack's state of charge?

1 / 1 point

Battery pack state of charge should be the average of the two cell states of charge (i.e., 50%)

Battery pack state of charge is 100% because we cannot charge the cell having state of charge of 100%

Battery pack state of charge is ill-defined, and the term should never be used

Battery pack state of charge is 0% because we cannot discharge the battery pack without damaging the cell having state of charge of 0%

Correct

Yes. For the very reason that none of the other responses to this question make physical sense, "battery pack state of charge" does not make physical sense and the term should not be used.