BATTERIESA. PREPARATION

1. Introduction and Motivation

2. Electrochemical Fundamentals

3. Helmholtz Equivalents for Nonlinear One-Ports

4 Battery Selection Basics

5. Battery Discharging and Charging

6. Typical Primary Cells

a. Daniell Cell

b. Weston Cell

c. Leclanché Cell

d. Mercury Cell

7. Typical Secondary Cells

a. Lead-Acid Cell

b. Nickel-Cadmium Cell

c. Sodium-Sulphur (Beta) Cell

8. References

B. EXPERIMENT

1. Equipment List

2. Advance Design

3. Preliminary Tests

4. Temperature Effects

5. Discharge Phenomena

6. Recharge Phenomena

7. Report

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B. EXPERIMENT

1. Equipment List

1 relay rack containing the usual lab gear

1 dual rheostat module1 temperature probe (Fluke 80T-150)

1 sealed 6 V battery (fully charged) (Universal UB685 equivalent to PS-682)1 sealed 6 V battery (fully charged) (Power-Sonic PS-610)

2. Advance Design

Be sure to review the following extremely useful document PRIOR to coming to lab:

PowerSonic Battery Technical Manual.

Your group will NOT be permitted to commence work until each of its members has submitted

a workable design for the following test apparatus to be used in the measurements!

Using components which you know to be available in the laboratory, design a convenient&

apparatus which will present a variable load to a 0-10 Volt DC source; this load shall have a

long-term current capacity of up to 9.0 Amp. Instrument this apparatus to provide accurate

measurements of source voltage and current.

3. Preliminary Tests

In this laboratory you will, in effect, be determining numerous quasi-global Thévenin

equivalents: that is, you will be determining v(i) characteristics and processing them to obtain

(0) = v(0)and (i) . In order to make these measurements in timely fashion, you need

a little practice. And that is the purpose of this section, which you must complete in no more

than thirty (30) minutes.

Connect a 6 VDC power supply, current-limited to approximately 500 mA, to the load you

designed. Determine v(i) of the supply from 0.0 A to 0.5 A in steps of 0.1 A. Take several

additional readings in the vicinity of 0.5 A where voltages drop to less than 6 VDC. Be sure you

can do this with alacrity (quick, lively action). Take no more points than are needed; but take

enough.

In addition, be certain that you are thoroughly familiar with the use of the

temperature probe.

& You have a lot of data to take. Therefore, safety and accuracy being assumed, experimental logistics rule!Batteries - 25

4. Temperature Effects

Approximately 30 min after the start of lab you will be provided with a sealed 6

Volt lead-acid battery (PS-610) which has been embedded in ice and thoroughly chilled

to a temperature below freezing.

Plop a small blob of thermal compound onto the top of the battery₤. Immediately

plug the temperature probe into the blob. Hold it there with a clamp standΔ. As soon as

an accurate temperature reading is available (perhaps 10 seconds), obtain with alacrity

(quick, lively action) a v(i) characteristic from 0.0 A to 2.0 A in steps of 0.4 A.

Terminate this test if v(i) falls below 4.50 V. Be sure to quickly record the temperature

associated with each data point. Then quickly disconnect the battery and proceed to

Part 5, except that (1) as soon as possible lift the battery out of its ice bath, pat it dry

with paper towels, and set it on the lab bench to warm up for at least 90 minutes and (2)

at the conclusion of Part 5, speedily repeat the above 0.0 to 2.0 Amp test.

5. Discharge Phenomena

While Part 4 is in its 90 min wait, put a UB685 battery into the load circuit and do

with alacrity (quick, lively action) a 0.0 to 9.0 Amp test using 1.0 A increments.

Terminate this test if v(i) falls below 4.50 V. Then set and maintain the discharge

current to a 4.6 Amp discharge rate (C-rate) and record v(0) and v(4.6) as functions of

time. Terminate this discharge test as soon as v(4.6) falls below 4.50 V. At once

repeat with alacrity the previous 0.0 to 9.0 Amp test on this battery.

6. Recharge Phenomena

After repeating the 0.0 to 2.0 Amp test on the warm PS-610 battery, connect the

UB685 battery to a power supply using a suitable ammeter and rheostat set to 50 .

Raise the power supply voltage level and simultaneously reduce the rheostat resistance

to 0 ohms to obtain an initial charging current of 0.80 A. Keep the supply voltage fixed

₤ Your lab group must also clean off ALL thermal compound from the battery at the end of the experiment. While you’re at it, clean off the temperature probe as well. Gaze on the mess, oh ye students, and despair.Δ This is not an ideal way of determining internal battery temperature; however, can you think of a better surrogate for the internal temperature of a sealed unit which can not readily be entered? A major inelegancy in this experiment is switching the UB685 from 4.6A to 0.0 A and back. It is suggested that you install a switch in the discharging (or charging) circuit using, for example, the Electrical Energy Monitor.

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at this level. At appropriate time intervals, measure i, v(i), and v(0). Continue this

recharge for at least 30 minutes.

This may not be as easy as you think! It turns out that the power supplies in use at this time (2001) seem to have an “eccentricity” which may cause them to crowbar even if the required current is well within their set range. Since there is no externally obvious reason for this behavior, it can cause consternation among students and faculty alike. Should you encounter such ostensibly bizarre behavior, try flipping the power supply on with its output voltage as low as possible and then slowly raising this voltage. It also helps to have a 100- rheostat in series with the battery and to lower its resistance after elevating the supply voltage. One prominent electronics manufacturer had an entire line of three-terminal voltage reulators fail in the marketplace as a result of such a quirk.

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7. Report

(a) Explain your 9 A variable resistance design.

(b) Plot the v(i) characteristic of the power supply. On the same plot show

(i). Comment tersely. Also, list and justify the criteria you employed in

satisfying the constraint “Take no more points than are needed.”

(c) Define the no load values of (0) = v(0) for the PS-610 battery at both

cold and room temperature. Plot v(i) for both the cold and room temperature

cases on the same graph. On a separate sheet, also plot the (i) curves

for both the cold and room temperature cases on the same graph. Comment

cogently. Was 90 minutes sufficient time for the battery to reach thermal

equilibration and how do you know?

(d) For the UB685, plot v(0.0) and v(4.6) as functions of time on the same graph

for the discharge and explain in detail why you chose the time points that you

did; also describe the test set-up design and operation and explain and justify

your protocol for measuring v(0.0). What was the total discharge time?

(e) Define the two no load values (fully charged and discharged) of (0) =

v(0). Plot v(i) for both the fully charged and discharged cases on the same

graph. On a separate sheet, also plot the fully charged and discharged (i)

curves on the same graph. Comment tersely#.

(f) Plot i, v(i) and v(0) versus time for the recharge on the same sheet. Comment

tersely. Note that v(i) should be nearly constant.

# It goes without saying that your terse comments should also be insight rich! Batteries - 28

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